Skip to main content

Functions

Functions

Detailed list of all functions for the Clarity language.

+ (add)

input: int, ... | uint, ...

output: int | uint

signature: (+ i1 i2...)

description:

Adds a variable number of integer inputs and returns the result. In the event of an overflow, throws a runtime error.

example:

(+ 1 2 3)   ;; Returns 6
(+ 2 3) ;; Returns 5
(+ 1 2 3 4) ;; Returns 10
(+ 9 -3) ;; Returns 6
(+ -3 -2) ;; Returns -5

- (subtract)

input: int, ... | uint, ...

output: int | uint

signature: (- i1 i2...)

description:

Subtracts a variable number of integer inputs and returns the result. In the event of an underflow, throws a runtime error.

example:

(- 2 1 1) ;; Returns 0
(- 0 3) ;; Returns -3
(- 5 -3) ;; Returns 8
(- -4 -5) ;; Returns 1

* (multiply)

input: int, ... | uint, ...

output: int | uint

signature: (* i1 i2...)

description:

Multiplies a variable number of integer inputs and returns the result. In the event of an overflow, throws a runtime error.

example:

(* 2 3)   ;; Returns 6
(* 5 2) ;; Returns 10
(* 2 2 2) ;; Returns 8
(* 3 -2) ;; Returns -6
(* -1 -2) ;; Returns 2

/ (divide)

input: int, ... | uint, ...

output: int | uint

signature: (/ i1 i2...)

description:

Divides a variable number of integer inputs and returns the integer part of the result. In the event of division by zero, throws a runtime error.

example:

(/ 2 3)    ;; Returns 0
(/ 5 2) ;; Returns 2
(/ 4 2 2) ;; Returns 1
(/ -10 2) ;; Returns -5
(/ -8 -2) ;; Returns 4
(/ -9 4) ;; Returns -2

>= (greater than or equal)

input: int, int | uint, uint

output: bool

signature: (>= i1 i2)

description:

Compares two integers, returning true if i1 is greater than or equal to i2 and false otherwise.

example:

(>= 1 1) ;; Returns true
(>= 5 2) ;; Returns true

<= (less than or equal)

input: int, int | uint, uint

output: bool

signature: (<= i1 i2)

description:

Compares two integers, returning true if i1 is less than or equal to i2 and false otherwise.

example:

(<= 1 1) ;; Returns true
(<= 5 2) ;; Returns false

< (less than)

input: int, int | uint, uint

output: bool

signature: (< i1 i2)

description:

Compares two integers, returning true if i1 is less than i2 and false otherwise.

example:

(< 1 2) ;; Returns true
(< 5 2) ;; Returns false

> (greater than)

input: int, int | uint, uint

output: bool

signature: (> i1 i2)

description:

Compares two integers, returning true if i1 is greater than i2 and false otherwise.

example:

(> 1 2) ;; Returns false
(> 5 2) ;; Returns true

to-int

input: uint

output: int

signature: (to-int u)

description:

Tries to convert the uint argument to an int. Will cause a runtime error and abort if the supplied argument is >= `pow(2, 127)``

example:

(to-int u238) ;; Returns 238

to-uint

input: int

output: uint

signature: (to-uint i)

description:

Tries to convert the int argument to a uint. Will cause a runtime error and abort if the supplied argument is negative.

example:

(to-uint 238) ;; Returns u238

mod

input: int, int | uint, uint

output: int | uint

signature: (mod i1 i2)

description:

Returns the integer remainder from integer dividing i1 by i2. In the event of a division by zero, throws a runtime error.

example:

(mod 2 3) ;; Returns 2
(mod 5 2) ;; Returns 1
(mod 7 1) ;; Returns 0

pow

input: int, int | uint, uint

output: int | uint

signature: (pow i1 i2)

description:

Returns the result of raising i1 to the power of i2. In the event of an overflow, throws a runtime error.

example:

(pow 2 3) ;; Returns 8
(pow 2 2) ;; Returns 4
(pow 7 1) ;; Returns 7

sqrti

input: int | uint

output: int | uint

signature: (sqrti n)

description:

Returns the largest integer that is less than or equal to the square root of n. Fails on a negative numbers.

example:

(sqrti u11) ;; Returns u3
(sqrti 1000000) ;; Returns 1000
(sqrti u1) ;; Returns u1
(sqrti 0) ;; Returns 0

log2

input: int | uint

output: int | uint

signature: (log2 n)

description:

Returns the integer part of the power to which the number 2 must be raised to obtain the value n. Fails on zero or a negative number.

example:

(log2 u8)   ;; Returns u3
(log2 8) ;; Returns 3
(log2 u1) ;; Returns u0
(log2 1000) ;; Returns 9

xor

input: int, int | uint, uint

output: int | uint

signature: (xor i1 i2)

description:

Returns the result of bitwise exclusive or'ing i1 with i2.

example:

(xor 1 2) ;; Returns 3
(xor 120 280) ;; Returns 352

and

input: bool, ...

output: bool

signature: (and b1 b2 ...)

description:

Returns true if all boolean inputs are true. Importantly, the supplied arguments are evaluated in-order and lazily. Lazy evaluation means that if one of the arguments returns false, the function short-circuits, and no subsequent arguments are evaluated.

example:

(and true false) ;; Returns false
(and (is-eq (+ 1 2) 1) (is-eq 4 4)) ;; Returns false
(and (is-eq (+ 1 2) 3) (is-eq 4 4)) ;; Returns true

or

input: bool, ...

output: bool

signature: (or b1 b2 ...)

description:

Returns true if any boolean inputs are true. Importantly, the supplied arguments are evaluated in-order and lazily. Lazy evaluation means that if one of the arguments returns true, the function short-circuits, and no subsequent arguments are evaluated.

example:

(or true false) ;; Returns true
(or (is-eq (+ 1 2) 1) (is-eq 4 4)) ;; Returns true
(or (is-eq (+ 1 2) 1) (is-eq 3 4)) ;; Returns false
(or (is-eq (+ 1 2) 3) (is-eq 4 4)) ;; Returns true

not

input: bool

output: bool

signature: (not b1)

description:

Returns the inverse of the boolean input.

example:

(not true) ;; Returns false
(not (is-eq 1 2)) ;; Returns true

is-eq

input: A, A, ...

output: bool

signature: (is-eq v1 v2...)

description:

Compares the inputted values, returning true if they are all equal. Note that unlike the (and ...) function, (is-eq ...) will not short-circuit. All values supplied to is-eq must be the same type.

example:

(is-eq 1 1) ;; Returns true
(is-eq true false) ;; Returns false
(is-eq \"abc\" 234 234) ;; Throws type error

if

input: bool, A, A

output: A

signature: (if bool1 expr1 expr2)

description:

The if function admits a boolean argument and two expressions which must return the same type. In the case that the boolean input is true, the if function evaluates and returns expr1. If the boolean input is false, the if function evaluates and returns expr2.

example:

(if true 1 2) ;; Returns 1
(if (> 1 2) 1 2) ;; Returns 2

let

input: ((name1 AnyType) (name2 AnyType) ...), AnyType, ... A

output: A

signature: (let ((name1 expr1) (name2 expr2) ...) expr-body1 expr-body2 ... expr-body-last)

description:

The let function accepts a list of variable name and expression pairs, evaluating each expression and binding it to the corresponding variable name. let bindings are sequential: when a let binding is evaluated, it may refer to prior binding. The context created by this set of bindings is used for evaluating its body expressions. The let expression returns the value of the last such body expression. Note: intermediary statements returning a response type must be checked`

example:

(let ((a 2) (b (+ 5 6 7))) (print a) (print b) (+ a b)) ;; Returns 20
(let ((a 5) (c (+ a 1)) (d (+ c 1)) (b (+ a c d))) (print a) (print b) (+ a b)) ;; Returns 23

map

input: Function(A, B, ..., N) -> X, sequence_A, sequence_B, ..., sequence_N

output: (list X)

signature: (map func sequence_A sequence_B ... sequence_N)

description:

The map function applies the function func to each corresponding element of the input sequences, and outputs a list of the same type containing the outputs from those function applications. Applicable sequence types are (list A), buff, string-ascii and string-utf8, for which the corresponding element types are, respectively, A, (buff 1), (string-ascii 1) and (string-utf8 1). The func argument must be a literal function name. Also, note that, no matter what kind of sequences the inputs are, the output is always a list.

example:

(map not (list true false true false)) ;; Returns (false true false true)
(map + (list 1 2 3) (list 1 2 3) (list 1 2 3)) ;; Returns (3 6 9)
(define-private (a-or-b (char (string-utf8 1))) (if (is-eq char u\"a\") u\"a\" u\"b\"))
(map a-or-b u\"aca\") ;; Returns (u\"a\" u\"b\" u\"a\")
(define-private (zero-or-one (char (buff 1))) (if (is-eq char 0x00) 0x00 0x01))
(map zero-or-one 0x000102) ;; Returns (0x00 0x01 0x01)

fold

input: Function(A, B) -> B, sequence_A, B

output: B

signature: (fold func sequence_A initial_B)

description:

The fold function condenses sequence_A into a value of type B by recursively applies the function func to each element of the input sequence and the output of a previous application of func.

fold uses initial_B in the initial application of func, along with the first element of sequence_A. The resulting value of type B is used for the next application of func, along with the next element of sequence_A and so on. fold returns the last value of type B returned by these successive applications func.

Applicable sequence types are (list A), buff, string-ascii and string-utf8, for which the corresponding element types are, respectively, A, (buff 1), (string-ascii 1) and (string-utf8 1). The func argument must be a literal function name.

example:

(fold * (list 2 2 2) 1) ;; Returns 8
(fold * (list 2 2 2) 0) ;; Returns 0
;; calculates (- 11 (- 7 (- 3 2)))
(fold - (list 3 7 11) 2) ;; Returns 5
(define-private (concat-string (a (string-ascii 20)) (b (string-ascii 20))) (unwrap-panic (as-max-len? (concat a b) u20)))
(fold concat-string \"cdef\" \"ab\") ;; Returns \"fedcab\"
(fold concat-string (list \"cd\" \"ef\") \"ab\") ;; Returns \"efcdab\"
(define-private (concat-buff (a (buff 20)) (b (buff 20))) (unwrap-panic (as-max-len? (concat a b) u20)))
(fold concat-buff 0x03040506 0x0102) ;; Returns 0x060504030102

append

input: list A, A

output: list

signature: (append (list 1 2 3 4) 5)

description:

The append function takes a list and another value with the same entry type, and outputs a list of the same type with max_len += 1.

example:

(append (list 1 2 3 4) 5) ;; Returns (1 2 3 4 5)

concat

input: sequence_A, sequence_A

output: sequence_A

signature: (concat sequence1 sequence2)

description:

The concat function takes two sequences of the same type, and returns a concatenated sequence of the same type, with the resulting sequence_len = sequence1_len + sequence2_len. Applicable sequence types are (list A), buff, string-ascii and string-utf8.

example:

(concat (list 1 2) (list 3 4)) ;; Returns (1 2 3 4)
(concat \"hello \" \"world\") ;; Returns \"hello world\"
(concat 0x0102 0x0304) ;; Returns 0x01020304

as-max-len?

input: sequence_A, uint

output: sequence_A

signature: (as-max-len? sequence max_length)

description:

The as-max-len? function takes a sequence argument and a uint-valued, literal length argument. The function returns an optional type. If the input sequence length is less than or equal to the supplied max_length, this returns (some sequence), otherwise it returns none. Applicable sequence types are (list A), buff, string-ascii and string-utf8. `

example:

(as-max-len? (list 2 2 2) u3) ;; Returns (some (2 2 2))
(as-max-len? (list 1 2 3) u2) ;; Returns none
(as-max-len? \"hello\" u10) ;; Returns (some \"hello\")
(as-max-len? 0x010203 u10) ;; Returns (some 0x010203)

len

input: sequence_A

output: uint

signature: (len sequence)

description:

The len function returns the length of a given sequence. Applicable sequence types are (list A), buff, string-ascii and string-utf8. `

example:

(len \"blockstack\") ;; Returns u10
(len (list 1 2 3 4 5)) ;; Returns u5
(len 0x010203) ;; Returns u3

element-at

input: sequence_A, uint

output: (optional A)

signature: (element-at sequence index)

description:

The element-at function returns the element at index in the provided sequence. Applicable sequence types are (list A), buff, string-ascii and string-utf8, for which the corresponding element types are, respectively, A, (buff 1), (string-ascii 1) and (string-utf8 1). `

example:

(element-at \"blockstack\" u5) ;; Returns (some \"s\")
(element-at (list 1 2 3 4 5) u5) ;; Returns none
(element-at (list 1 2 3 4 5) (+ u1 u2)) ;; Returns (some 4)
(element-at \"abcd\" u1) ;; Returns (some \"b\")
(element-at 0xfb01 u1) ;; Returns (some 0x01)

index-of

input: sequence_A, A

output: (optional uint)

signature: (index-of sequence item)

description:

The index-of function returns the first index at which item can be found, using is-eq checks, in the provided sequence. Applicable sequence types are (list A), buff, string-ascii and string-utf8, for which the corresponding element types are, respectively, A, (buff 1), (string-ascii 1) and (string-utf8 1). If the target item is not found in the sequence (or if an empty string or buffer is supplied), this function returns none.

example:

(index-of \"blockstack\" \"b\") ;; Returns (some u0)
(index-of \"blockstack\" \"k\") ;; Returns (some u4)
(index-of \"blockstack\" \"\") ;; Returns none
(index-of (list 1 2 3 4 5) 6) ;; Returns none
(index-of 0xfb01 0x01) ;; Returns (some u1)

list

input: A, ...

output: (list A)

signature: (list expr1 expr2 expr3 ...)

description:

The list function constructs a list composed of the inputted values. Each supplied value must be of the same type.

example:

(list (+ 1 2) 4 5) ;; Returns (3 4 5)

var-get

input: VarName

output: A

signature: (var-get var-name)

description:

The var-get function looks up and returns an entry from a contract's data map. The value is looked up using var-name.

example:

(define-data-var cursor int 6)
(var-get cursor) ;; Returns 6

var-set

input: VarName, AnyType

output: bool

signature: (var-set var-name expr1)

description:

The var-set function sets the value associated with the input variable to the inputted value. The function always returns true.

example:

(define-data-var cursor int 6)
(var-get cursor) ;; Returns 6
(var-set cursor (+ (var-get cursor) 1)) ;; Returns true
(var-get cursor) ;; Returns 7

map-get?

input: MapName, tuple

output: (optional (tuple))

signature: (map-get? map-name key-tuple)

description:

The map-get? function looks up and returns an entry from a contract's data map. The value is looked up using key-tuple. If there is no value associated with that key in the data map, the function returns a none option. Otherwise, it returns (some value).

example:

(define-map names-map { name: (string-ascii 10) } { id: int })
(map-set names-map { name: \"blockstack\" } { id: 1337 })
(map-get? names-map (tuple (name \"blockstack\"))) ;; Returns (some (tuple (id 1337)))
(map-get? names-map { name: \"blockstack\" }) ;; Same command, using a shorthand for constructing the tuple

map-set

input: MapName, tuple_A, tuple_B

output: bool

signature: (map-set map-name key-tuple value-tuple)

description:

The map-set function sets the value associated with the input key to the inputted value. This function performs a blind update; whether or not a value is already associated with the key, the function overwrites that existing association.

Note: the value-tuple requires 1 additional byte for storage in the materialized blockchain state, and therefore the maximum size of a value that may be inserted into a map is MAX_CLARITY_VALUE - 1.

example:

(define-map names-map { name: (string-ascii 10) } { id: int })
(map-set names-map { name: \"blockstack\" } { id: 1337 }) ;; Returns true
(map-set names-map (tuple (name \"blockstack\")) (tuple (id 1337))) ;; Same command, using a shorthand for constructing the tuple

map-insert

input: MapName, tuple_A, tuple_B

output: bool

signature: (map-insert map-name key-tuple value-tuple)

description:

The map-insert function sets the value associated with the input key to the inputted value if and only if there is not already a value associated with the key in the map. If an insert occurs, the function returns true. If a value already existed for this key in the data map, the function returns false.

Note: the value-tuple requires 1 additional byte for storage in the materialized blockchain state, and therefore the maximum size of a value that may be inserted into a map is MAX_CLARITY_VALUE - 1.

example:

(define-map names-map { name: (string-ascii 10) } { id: int })
(map-insert names-map { name: \"blockstack\" } { id: 1337 }) ;; Returns true
(map-insert names-map { name: \"blockstack\" } { id: 1337 }) ;; Returns false
(map-insert names-map (tuple (name \"blockstack\")) (tuple (id 1337))) ;; Same command, using a shorthand for constructing the tuple

map-delete

input: MapName, tuple

output: bool

signature: (map-delete map-name key-tuple)

description:

The map-delete function removes the value associated with the input key for the given map. If an item exists and is removed, the function returns true. If a value did not exist for this key in the data map, the function returns false.

example:

(define-map names-map { name: (string-ascii 10) } { id: int })
(map-insert names-map { name: \"blockstack\" } { id: 1337 }) ;; Returns true
(map-delete names-map { name: \"blockstack\" }) ;; Returns true
(map-delete names-map { name: \"blockstack\" }) ;; Returns false
(map-delete names-map (tuple (name \"blockstack\"))) ;; Same command, using a shorthand for constructing the tuple

tuple

input: (key-name A), (key-name-2 B), ...

output: (tuple (key-name A) (key-name-2 B) ...)

signature: (tuple (key0 expr0) (key1 expr1) ...)

description:

The tuple special form constructs a typed tuple from the supplied key and expression pairs. A get function can use typed tuples as input to select specific values from a given tuple. Key names may not appear multiple times in the same tuple definition. Supplied expressions are evaluated and associated with the expressions' paired key name.

There is a shorthand using curly brackets of the form {key0: expr0, key1: expr, ...}`

example:

(tuple (name \"blockstack\") (id 1337)) ;; using tuple
{name: \"blockstack\", id: 1337} ;; using curly brackets

get

input: KeyName, (tuple) | (optional (tuple))

output: A

signature: (get key-name tuple)

description:

The get function fetches the value associated with a given key from the supplied typed tuple. If an Optional value is supplied as the inputted tuple, get returns an Optional type of the specified key in the tuple. If the supplied option is a (none) option, get returns (none).

example:

(define-map names-map { name: (string-ascii 12) } { id: int })
(map-insert names-map { name: \"blockstack\" } { id: 1337 }) ;; Returns true
(get id (tuple (name \"blockstack\") (id 1337))) ;; Returns 1337
(get id (map-get? names-map (tuple (name \"blockstack\")))) ;; Returns (some 1337)
(get id (map-get? names-map (tuple (name \"non-existent\")))) ;; Returns none

merge

input: tuple, tuple

output: tuple

signature: (merge tuple { key1: val1 })

description:

The merge function returns a new tuple with the combined fields, without mutating the supplied tuples.

example:

(define-map users { id: int } { name: (string-ascii 12), address: (optional principal) })
(map-insert users { id: 1337 } { name: \"john\", address: none }) ;; Returns true
(let ((user (unwrap-panic (map-get? users { id: 1337 }))))
(merge user { address: (some 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) })) ;; Returns (tuple (address (some SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF)) (name \"john\"))

begin

input: AnyType, ... A

output: A

signature: (begin expr1 expr2 expr3 ... expr-last)

description:

The begin function evaluates each of its input expressions, returning the return value of the last such expression. Note: intermediary statements returning a response type must be checked.

example:

(begin (+ 1 2) 4 5) ;; Returns 5

hash160

input: buff|uint|int

output: (buff 20)

signature: (hash160 value)

description:

The hash160 function computes RIPEMD160(SHA256(x)) of the inputted value. If an integer (128 bit) is supplied the hash is computed over the little-endian representation of the integer.

example:

(hash160 0) ;; Returns 0xe4352f72356db555721651aa612e00379167b30f

sha256

input: buff|uint|int

output: (buff 32)

signature: (sha256 value)

description:

The sha256 function computes SHA256(x) of the inputted value. If an integer (128 bit) is supplied the hash is computed over the little-endian representation of the integer.

example:

(sha256 0) ;; Returns 0x374708fff7719dd5979ec875d56cd2286f6d3cf7ec317a3b25632aab28ec37bb

sha512

input: buff|uint|int

output: (buff 64)

signature: (sha512 value)

description:

The sha512 function computes SHA512(x) of the inputted value. If an integer (128 bit) is supplied the hash is computed over the little-endian representation of the integer.

example:

(sha512 1) ;; Returns 0x6fcee9a7b7a7b821d241c03c82377928bc6882e7a08c78a4221199bfa220cdc55212273018ee613317c8293bb8d1ce08d1e017508e94e06ab85a734c99c7cc34

sha512/256

input: buff|uint|int

output: (buff 32)

signature: (sha512/256 value)

description:

The sha512/256 function computes SHA512/256(x) (the SHA512 algorithm with the 512/256 initialization vector, truncated to 256 bits) of the inputted value. If an integer (128 bit) is supplied the hash is computed over the little-endian representation of the integer.

example:

(sha512/256 1) ;; Returns 0x515a7e92e7c60522db968d81ff70b80818fc17aeabbec36baf0dda2812e94a86

keccak256

input: buff|uint|int

output: (buff 32)

signature: (keccak256 value)

description:

The keccak256 function computes KECCAK256(value) of the inputted value. Note that this differs from the NIST SHA-3 (that is, FIPS 202) standard. If an integer (128 bit) is supplied the hash is computed over the little-endian representation of the integer.

example:

(keccak256 0) ;; Returns 0xf490de2920c8a35fabeb13208852aa28c76f9be9b03a4dd2b3c075f7a26923b4

secp256k1-recover?

input: (buff 32), (buff 65)

output: (response (buff 33) uint)

signature: (secp256k1-recover? message-hash signature)

description:

The secp256k1-recover? function recovers the public key used to sign the message which sha256 is message-hash with the provided signature. If the signature does not match, it will return the error code (err u1).. If the signature is invalid, it will return the error code (err u2).. The signature includes 64 bytes plus an additional recovery id (00..03) for a total of 65 bytes.

example:

(secp256k1-recover? 0xde5b9eb9e7c5592930eb2e30a01369c36586d872082ed8181ee83d2a0ec20f04
0x8738487ebe69b93d8e51583be8eee50bb4213fc49c767d329632730cc193b873554428fc936ca3569afc15f1c9365f6591d6251a89fee9c9ac661116824d3a1301)
;; Returns (ok 0x03adb8de4bfb65db2cfd6120d55c6526ae9c52e675db7e47308636534ba7786110)

secp256k1-verify

input: (buff 32), (buff 64) | (buff 65), (buff 33)

output: bool

signature: (secp256k1-verify message-hash signature public-key)

description:

The secp256k1-verify function verifies that the provided signature of the message-hash was signed with the private key that generated the public key. The message-hash is the sha256 of the message. The signature includes 64 bytes plus an optional additional recovery id (00..03) for a total of 64 or 65 bytes.

example:

(secp256k1-verify 0xde5b9eb9e7c5592930eb2e30a01369c36586d872082ed8181ee83d2a0ec20f04
0x8738487ebe69b93d8e51583be8eee50bb4213fc49c767d329632730cc193b873554428fc936ca3569afc15f1c9365f6591d6251a89fee9c9ac661116824d3a1301
0x03adb8de4bfb65db2cfd6120d55c6526ae9c52e675db7e47308636534ba7786110) ;; Returns true
(secp256k1-verify 0xde5b9eb9e7c5592930eb2e30a01369c36586d872082ed8181ee83d2a0ec20f04
0x8738487ebe69b93d8e51583be8eee50bb4213fc49c767d329632730cc193b873554428fc936ca3569afc15f1c9365f6591d6251a89fee9c9ac661116824d3a13
0x03adb8de4bfb65db2cfd6120d55c6526ae9c52e675db7e47308636534ba7786110) ;; Returns true
(secp256k1-verify 0x0000000000000000000000000000000000000000000000000000000000000000
0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
0x03adb8de4bfb65db2cfd6120d55c6526ae9c52e675db7e47308636534ba7786110) ;; Returns false

print

input: A

output: A

signature: (print expr)

description:

The print function evaluates and returns its input expression. On Stacks Core nodes configured for development (as opposed to production mining nodes), this function prints the resulting value to STDOUT (standard output).

example:

(print (+ 1 2 3)) ;; Returns 6

contract-call?

input: ContractName, PublicFunctionName, Arg0, ...

output: (response A B)

signature: (contract-call? .contract-name function-name arg0 arg1 ...)

description:

The contract-call? function executes the given public function of the given contract. You may not use this function to call a public function defined in the current contract. If the public function returns err, any database changes resulting from calling contract-call? are aborted. If the function returns ok, database changes occurred.

example:


;; instantiate the sample-contracts/tokens.clar contract first!
(as-contract (contract-call? .tokens mint! u19)) ;; Returns (ok u19)

as-contract

input: A

output: A

signature: (as-contract expr)

description:

The as-contract function switches the current context's tx-sender value to the contract's principal and executes expr with that context. It returns the resulting value of expr.

example:

(as-contract tx-sender) ;; Returns S1G2081040G2081040G2081040G208105NK8PE5.docs-test

contract-of

input: Trait

output: principal

signature: (contract-of .contract-name)

description:

The contract-of function returns the principal of the contract implementing the trait.

example:

(use-trait token-a-trait 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF.token-a.token-trait)
(define-public (forward-get-balance (user principal) (contract <token-a-trait>))
(begin
(ok (contract-of contract)))) ;; returns the principal of the contract implementing <token-a-trait>

principal-of?

input: (buff 33)

output: (response principal uint)

signature: (principal-of? public-key)

description:

The principal-of? function returns the principal derived from the provided public key. If the public-key is invalid, it will return the error code (err u1).. `

example:

(principal-of? 0x03adb8de4bfb65db2cfd6120d55c6526ae9c52e675db7e47308636534ba7786110) ;; Returns (ok ST1AW6EKPGT61SQ9FNVDS17RKNWT8ZP582VF9HSCP)

at-block

input: (buff 32), A

output: A

signature: (at-block id-block-hash expr)

description:

The at-block function evaluates the expression expr as if it were evaluated at the end of the block indicated by the block-hash argument. The expr closure must be read-only.

Note: The block identifying hash must be a hash returned by the id-header-hash block information property. This hash uniquely identifies Stacks blocks and is unique across Stacks forks. While the hash returned by header-hash is unique within the context of a single fork, it is not unique across Stacks forks.

The function returns the result of evaluating expr.

example:

(define-data-var data int 1)
(at-block 0x0000000000000000000000000000000000000000000000000000000000000000 block-height) ;; Returns u0
(at-block (get-block-info? id-header-hash 0) (var-get data)) ;; Throws NoSuchDataVariable because `data` wasn't initialized at block height 0

get-block-info?

input: BlockInfoPropertyName, BlockHeightInt

output: (optional buff) | (optional uint)

signature: (get-block-info? prop-name block-height-expr)

description:

The get-block-info? function fetches data for a block of the given block height. The value and type returned are determined by the specified BlockInfoPropertyName. If the provided BlockHeightInt does not correspond to an existing block prior to the current block, the function returns none. The currently available property names are time, header-hash, burnchain-header-hash, id-header-hash, miner-address, and vrf-seed.

The time property returns an integer value of the block header time field. This is a Unix epoch timestamp in seconds which roughly corresponds to when the block was mined. Warning: this does not increase monotonically with each block and block times are accurate only to within two hours. See BIP113 for more information.

The header-hash, burnchain-header-hash, id-header-hash, and vrf-seed properties return a 32-byte buffer.

The miner-address property returns a principal corresponding to the miner of the given block.

The id-header-hash is the block identifier value that must be used as input to the at-block function.

example:

(get-block-info? time u0) ;; Returns (some u1557860301)
(get-block-info? header-hash u0) ;; Returns (some 0x374708fff7719dd5979ec875d56cd2286f6d3cf7ec317a3b25632aab28ec37bb)
(get-block-info? vrf-seed u0) ;; Returns (some 0xf490de2920c8a35fabeb13208852aa28c76f9be9b03a4dd2b3c075f7a26923b4)

err

input: A

output: (response A B)

signature: (err value)

description:

The err function constructs a response type from the input value. Use err for creating return values in public functions. An err value indicates that any database changes during the processing of the function should be rolled back.

example:

(err true) ;; Returns (err true)

ok

input: A

output: (response A B)

signature: (ok value)

description:

The ok function constructs a response type from the input value. Use ok for creating return values in public functions. An ok value indicates that any database changes during the processing of the function should materialize.

example:

(ok 1) ;; Returns (ok 1)

some

input: A

output: (optional A)

signature: (some value)

description:

The some function constructs a optional type from the input value.

example:

(some 1) ;; Returns (some 1)
(is-none (some 2)) ;; Returns false

default-to

input: A, (optional A)

output: A

signature: (default-to default-value option-value)

description:

The default-to function attempts to 'unpack' the second argument: if the argument is a (some ...) option, it returns the inner value of the option. If the second argument is a (none) value, default-to it returns the value of default-value.

example:

(define-map names-map { name: (string-ascii 12) } { id: int })
(map-set names-map { name: \"blockstack\" } { id: 1337 })
(default-to 0 (get id (map-get? names-map (tuple (name \"blockstack\"))))) ;; Returns 1337
(default-to 0 (get id (map-get? names-map (tuple (name \"non-existant\"))))) ;; Returns 0

asserts!

input: bool, C

output: bool

signature: (asserts! bool-expr thrown-value)

description:

The asserts! function admits a boolean argument and asserts its evaluation: if bool-expr is true, asserts! returns true and proceeds in the program execution. If the supplied argument is returning a false value, asserts! returns thrown-value and exits the current control-flow.

example:

(asserts! (is-eq 1 1) (err 1)) ;; Returns true

unwrap!

input: (optional A) | (response A B), C

output: A

signature: (unwrap! option-input thrown-value)

description:

The unwrap! function attempts to 'unpack' the first argument: if the argument is an option type, and the argument is a (some ...) option, unwrap! returns the inner value of the option. If the argument is a response type, and the argument is an (ok ...) response, unwrap! returns the inner value of the ok. If the supplied argument is either an (err ...) or a (none) value, unwrap! returns thrown-value from the current function and exits the current control-flow.

example:

(define-map names-map { name: (string-ascii 12) } { id: int })
(map-set names-map { name: \"blockstack\" } { id: 1337 })
(define-private (get-name-or-err (name (string-ascii 12)))
(let ((raw-name (unwrap! (map-get? names-map { name: name }) (err 1))))
(ok raw-name)))

(get-name-or-err \"blockstack\") ;; Returns (ok (tuple (id 1337)))
(get-name-or-err \"non-existant\") ;; Returns (err 1)

unwrap-err!

input: (response A B), C

output: B

signature: (unwrap-err! response-input thrown-value)

description:

The unwrap-err! function attempts to 'unpack' the first argument: if the argument is an (err ...) response, unwrap-err! returns the inner value of the err. If the supplied argument is an (ok ...) value, unwrap-err! returns thrown-value from the current function and exits the current control-flow.

example:

(unwrap-err! (err 1) false) ;; Returns 1

unwrap-panic

input: (optional A) | (response A B)

output: A

signature: (unwrap-panic option-input)

description:

The unwrap function attempts to 'unpack' its argument: if the argument is an option type, and the argument is a (some ...) option, this function returns the inner value of the option. If the argument is a response type, and the argument is an (ok ...) response, it returns the inner value of the ok. If the supplied argument is either an (err ...) or a (none) value, unwrap throws a runtime error, aborting any further processing of the current transaction.

example:

(define-map names-map { name: (string-ascii 12) } { id: int })
(map-set names-map { name: \"blockstack\" } { id: 1337 })
(unwrap-panic (map-get? names-map { name: \"blockstack\" })) ;; Returns (tuple (id 1337))
(unwrap-panic (map-get? names-map { name: \"non-existant\" })) ;; Throws a runtime exception

unwrap-err-panic

input: (response A B)

output: B

signature: (unwrap-err-panic response-input)

description:

The unwrap-err function attempts to 'unpack' the first argument: if the argument is an (err ...) response, unwrap returns the inner value of the err. If the supplied argument is an (ok ...) value, unwrap-err throws a runtime error, aborting any further processing of the current transaction.

example:

(unwrap-err-panic (err 1)) ;; Returns 1
(unwrap-err-panic (ok 1)) ;; Throws a runtime exception

match

input: (optional A) name expression expression | (response A B) name expression name expression

output: C

signature: `(match opt-input some-binding-name some-branch none-branch) |

(match-resp input ok-binding-name ok-branch err-binding-name err-branch)`

description:

The match function is used to test and destructure optional and response types.

If the input is an optional, it tests whether the provided input is a some or none option, and evaluates some-branch or none-branch in each respective case.

Within the some-branch, the contained value of the input argument is bound to the provided some-binding-name name.

Only one of the branches will be evaluated (similar to if statements).

If the input is a response, it tests whether the provided input is an ok or err response type, and evaluates ok-branch or err-branch in each respective case.

Within the ok-branch, the contained ok value of the input argument is bound to the provided ok-binding-name name.

Within the err-branch, the contained err value of the input argument is bound to the provided err-binding-name name.

Only one of the branches will be evaluated (similar to if statements).

Note: Type checking requires that the type of both the ok and err parts of the response object be determinable. For situations in which one of the parts of a response is untyped, you should use unwrap-panic or unwrap-err-panic instead of match.

example:


(define-private (add-10 (x (optional int)))
(match x
value (+ 10 value)
10))
(add-10 (some 5)) ;; Returns 15
(add-10 none) ;; Returns 10

(define-private (add-or-pass-err (x (response int (string-ascii 10))) (to-add int))
(match x
value (ok (+ to-add value))
err-value (err err-value)))
(add-or-pass-err (ok 5) 20) ;; Returns (ok 25)
(add-or-pass-err (err \"ERROR\") 20) ;; Returns (err \"ERROR\")

try!

input: (optional A) | (response A B)

output: A

signature: (try! option-input)

description:

The try! function attempts to 'unpack' the first argument: if the argument is an option type, and the argument is a (some ...) option, try! returns the inner value of the option. If the argument is a response type, and the argument is an (ok ...) response, try! returns the inner value of the ok. If the supplied argument is either an (err ...) or a none value, try! returns either none or the (err ...) value from the current function and exits the current control-flow.

example:

(define-map names-map { name: (string-ascii 12) } { id: int })
(map-set names-map { name: \"blockstack\" } { id: 1337 })
(try! (map-get? names-map { name: \"blockstack\" })) ;; Returns (tuple (id 1337))
(define-private (checked-even (x int))
(if (is-eq (mod x 2) 0)
(ok x)
(err false)))
(define-private (double-if-even (x int))
(ok (* 2 (try! (checked-even x)))))
(double-if-even 10) ;; Returns (ok 20)
(double-if-even 3) ;; Returns (err false)

is-ok

input: (response A B)

output: bool

signature: (is-ok value)

description:

is-ok tests a supplied response value, returning true if the response was ok, and false if it was an err.

example:

(is-ok (ok 1)) ;; Returns true
(is-ok (err 1)) ;; Returns false

is-none

input: (optional A)

output: bool

signature: (is-none value)

description:

is-none tests a supplied option value, returning true if the option value is (none), and false if it is a (some ...).

example:

(define-map names-map { name: (string-ascii 12) } { id: int })
(map-set names-map { name: \"blockstack\" } { id: 1337 })
(is-none (get id (map-get? names-map { name: \"blockstack\" }))) ;; Returns false
(is-none (get id (map-get? names-map { name: \"non-existant\" }))) ;; Returns true

is-err

input: (response A B)

output: bool

signature: (is-err value)

description:

is-err tests a supplied response value, returning true if the response was an err, and false if it was an ok.

example:

(is-err (ok 1)) ;; Returns false
(is-err (err 1)) ;; Returns true

is-some

input: (optional A)

output: bool

signature: (is-some value)

description:

is-some tests a supplied option value, returning true if the option value is (some ...), and false if it is a none.

example:


(define-map names-map { name: (string-ascii 12) } { id: int })
(map-set names-map { name: \"blockstack\" } { id: 1337 })
(is-some (get id (map-get? names-map { name: \"blockstack\" }))) ;; Returns true
(is-some (get id (map-get? names-map { name: \"non-existant\" }))) ;; Returns false

filter

input: Function(A) -> bool, sequence_A

output: sequence_A

signature: (filter func sequence)

description:

The filter function applies the input function func to each element of the input sequence, and returns the same sequence with any elements removed for which func returned false. Applicable sequence types are (list A), buff, string-ascii and string-utf8, for which the corresponding element types are, respectively, A, (buff 1), (string-ascii 1) and (string-utf8 1). The func argument must be a literal function name. `

example:


(filter not (list true false true false)) ;; Returns (false false)
(define-private (is-a (char (string-utf8 1))) (is-eq char u\"a\"))
(filter is-a u\"acabd\") ;; Returns u\"aa\"
(define-private (is-zero (char (buff 1))) (is-eq char 0x00))
(filter is-zero 0x00010002) ;; Returns 0x0000

ft-get-balance

input: TokenName, principal

output: uint

signature: (ft-get-balance token-name principal)

description:

ft-get-balance returns token-name balance of the principal principal. The token type must have been defined using define-fungible-token.

example:

(define-fungible-token stackaroo)
(ft-mint? stackaroo u100 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR)
(ft-get-balance stackaroo 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR) ;; Returns u100

nft-get-owner?

input: AssetName, A

output: (optional principal)

signature: (nft-get-owner? asset-class asset-identifier)

description:

nft-get-owner? returns the owner of an asset, identified by asset-identifier, or none if the asset does not exist. The asset type must have been defined using define-non-fungible-token, and the supplied asset-identifier must be of the same type specified in that definition.

example:

(define-non-fungible-token stackaroo (string-ascii 40))
(nft-mint? stackaroo \"Roo\" 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF)
(nft-get-owner? stackaroo \"Roo\") ;; Returns (some SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF)
(nft-get-owner? stackaroo \"Too\") ;; Returns none

ft-transfer?

input: TokenName, uint, principal, principal

output: (response bool uint)

signature: (ft-transfer? token-name amount sender recipient)

description:

ft-transfer? is used to increase the token balance for the recipient principal for a token type defined using define-fungible-token by debiting the sender principal. In contrast to stx-transfer?, any user can transfer the assets. When used, relevant guards need to be added.

This function returns (ok true) if the transfer is successful. In the event of an unsuccessful transfer it returns one of the following error codes:

(err u1) -- sender does not have enough balance to transfer (err u2) -- sender and recipient are the same principal (err u3) -- amount to send is non-positive `

example:

(define-fungible-token stackaroo)
(ft-mint? stackaroo u100 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR)
(ft-transfer? stackaroo u50 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) ;; Returns (ok true)
(ft-transfer? stackaroo u60 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) ;; Returns (err u1)

nft-transfer?

input: AssetName, A, principal, principal

output: (response bool uint)

signature: (nft-transfer? asset-class asset-identifier sender recipient)

description:

nft-transfer? is used to change the owner of an asset identified by asset-identifier from sender to recipient. The asset-class must have been defined by define-non-fungible-token and asset-identifier must be of the type specified in that definition. In contrast to stx-transfer?, any user can transfer the asset. When used, relevant guards need to be added.

This function returns (ok true) if the transfer is successful. In the event of an unsuccessful transfer it returns one of the following error codes:

(err u1) -- sender does not own the asset (err u2) -- sender and recipient are the same principal (err u3) -- asset identified by asset-identifier does not exist `

example:

(define-non-fungible-token stackaroo (string-ascii 40))
(nft-mint? stackaroo \"Roo\" 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR)
(nft-transfer? stackaroo \"Roo\" 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) ;; Returns (ok true)
(nft-transfer? stackaroo \"Roo\" 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) ;; Returns (err u1)
(nft-transfer? stackaroo \"Stacka\" 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) ;; Returns (err u3)

nft-mint?

input: AssetName, A, principal

output: (response bool uint)

signature: (nft-mint? asset-class asset-identifier recipient)

description:

nft-mint? is used to instantiate an asset and set that asset's owner to the recipient principal. The asset must have been defined using define-non-fungible-token, and the supplied asset-identifier must be of the same type specified in that definition.

If an asset identified by asset-identifier already exists, this function will return an error with the following error code:

(err u1)

Otherwise, on successfuly mint, it returns (ok true). `

example:

(define-non-fungible-token stackaroo (string-ascii 40))
(nft-mint? stackaroo \"Roo\" 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) ;; Returns (ok true)

ft-mint?

input: TokenName, uint, principal

output: (response bool uint)

signature: (ft-mint? token-name amount recipient)

description:

ft-mint? is used to increase the token balance for the recipient principal for a token type defined using define-fungible-token. The increased token balance is not transfered from another principal, but rather minted.

If a non-positive amount is provided to mint, this function returns (err 1). Otherwise, on successfuly mint, it returns (ok true). `

example:

(define-fungible-token stackaroo)
(ft-mint? stackaroo u100 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) ;; Returns (ok true)

ft-get-supply

input: TokenName

output: uint

signature: (ft-get-supply token-name)

description:

ft-get-balance returns token-name circulating supply. The token type must have been defined using define-fungible-token.

example:

(define-fungible-token stackaroo)
(ft-mint? stackaroo u100 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR)
(ft-get-supply stackaroo) ;; Returns u100

ft-burn?

input: TokenName, uint, principal

output: (response bool uint)

signature: (ft-burn? token-name amount sender)

description:

ft-burn? is used to decrease the token balance for the sender principal for a token type defined using define-fungible-token. The decreased token balance is not transfered to another principal, but rather destroyed, reducing the circulating supply.

If a non-positive amount is provided to burn, this function returns (err 1). Otherwise, on successfuly burn, it returns (ok true).

example:


(define-fungible-token stackaroo)
(ft-mint? stackaroo u100 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) ;; Returns (ok true)
(ft-burn? stackaroo u50 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) ;; Returns (ok true)

nft-burn?

input: AssetName, A, principal

output: (response bool uint)

signature: (nft-burn? asset-class asset-identifier recipient)

description:

nft-burn? is used to burn an asset and remove that asset's owner from the recipient principal. The asset must have been defined using define-non-fungible-token, and the supplied asset-identifier must be of the same type specified in that definition.

If an asset identified by asset-identifier doesn't exist, this function will return an error with the following error code:

(err u1)

Otherwise, on successfuly burn, it returns (ok true). `

example:

(define-non-fungible-token stackaroo (string-ascii 40))
(nft-mint? stackaroo \"Roo\" 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) ;; Returns (ok true)
(nft-burn? stackaroo \"Roo\" 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF) ;; Returns (ok true)

stx-get-balance

input: principal

output: uint

signature: (stx-get-balance owner)

description:

stx-get-balance is used to query the STX balance of the owner principal.

This function returns the STX balance of the owner principal. In the event that the owner principal isn't materialized, it returns 0.

example:

(stx-get-balance 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR) ;; Returns u0
(stx-get-balance (as-contract tx-sender)) ;; Returns u1000

stx-transfer?

input: uint, principal, principal

output: (response bool uint)

signature: (stx-transfer? amount sender recipient)

description:

stx-transfer? is used to increase the STX balance for the recipient principal by debiting the sender principal. The sender principal must be equal to the current context's tx-sender.

This function returns (ok true) if the transfer is successful. In the event of an unsuccessful transfer it returns one of the following error codes:

(err u1) -- sender does not have enough balance to transfer (err u2) -- sender and recipient are the same principal (err u3) -- amount to send is non-positive (err u4) -- the sender principal is not the current tx-sender

example:


(as-contract
(stx-transfer? u60 tx-sender 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR)) ;; Returns (ok true)
(as-contract
(stx-transfer? u50 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR tx-sender)) ;; Returns (err u4)

stx-burn?

input: uint, principal

output: (response bool uint)

signature: (stx-burn? amount sender)

description:

stx-burn? debits the sender principal's STX holdings by amount, destroying the STX. The sender principal must be equal to the current context's tx-sender.

This function returns (ok true) if the transfer is successful. In the event of an unsuccessful transfer it returns one of the following error codes:

(err u1) -- sender does not have enough balance to transfer (err u3) -- amount to send is non-positive (err u4) -- the sender principal is not the current tx-sender

example:

(as-contract
(stx-burn? u60 tx-sender)) ;; Returns (ok true)
(as-contract
(stx-burn? u50 'SZ2J6ZY48GV1EZ5V2V5RB9MP66SW86PYKKQ9H6DPR)) ;; Returns (err u4)

define-constant

input: MethodSignature, MethodBody

output: Not Applicable

signature: (define-constant name expression)

description:

define-constant is used to define a private constant value in a smart contract. The expression passed into the definition is evaluated at contract launch, in the order that it is supplied in the contract. This can lead to undefined function or undefined variable errors in the event that a function or variable used in the expression has not been defined before the constant.

Like other kinds of definition statements, define-constant may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).

example:


(define-constant four (+ 2 2))
(+ 4 four) ;; Returns 8

define-private

input: MethodSignature, MethodBody

output: Not Applicable

signature: (define-private (function-name (arg-name-0 arg-type-0) (arg-name-1 arg-type-1) ...) function-body)

description:

define-private is used to define private functions for a smart contract. Private functions may not be called from other smart contracts, nor may they be invoked directly by users. Instead, these functions may only be invoked by other functions defined in the same smart contract.

Like other kinds of definition statements, define-private may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).

Private functions may return any type.

example:

(define-private (max-of (i1 int) (i2 int))
(if (> i1 i2)
i1
i2))
(max-of 4 6) ;; Returns 6

define-public

input: MethodSignature, MethodBody

output: Not Applicable

signature: (define-public (function-name (arg-name-0 arg-type-0) (arg-name-1 arg-type-1) ...) function-body)

description:

define-public is used to define a public function and transaction for a smart contract. Public functions are callable from other smart contracts and may be invoked directly by users by submitting a transaction to the Stacks blockchain.

Like other kinds of definition statements, define-public may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).

Public functions must return a ResponseType (using either ok or err). Any datamap modifications performed by a public function is aborted if the function returns an err type. Public functions may be invoked by other contracts via contract-call?.

example:

(define-public (hello-world (input int))
(begin (print (+ 2 input))
(ok input)))

define-read-only

input: MethodSignature, MethodBody

output: Not Applicable

signature: (define-read-only (function-name (arg-name-0 arg-type-0) (arg-name-1 arg-type-1) ...) function-body)

description:

define-read-only is used to define a public read-only function for a smart contract. Such functions are callable from other smart contracts.

Like other kinds of definition statements, define-read-only may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).

Read-only functions may return any type. However, read-only functions may not perform any datamap modifications, or call any functions which perform such modifications. This is enforced both during type checks and during the execution of the function. Public read-only functions may be invoked by other contracts via contract-call?.

example:

(define-read-only (just-return-one-hundred)
(* 10 10))

define-map

input: MapName, TypeDefinition, TypeDefinition

output: Not Applicable

signature: (define-map map-name key-type value-type)

description:

define-map is used to define a new datamap for use in a smart contract. Such maps are only modifiable by the current smart contract.

Maps are defined with a key type and value type, often these types are tuple types.

Like other kinds of definition statements, define-map may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).

example:

(define-map squares { x: int } { square: int })
(define-private (add-entry (x int))
(map-insert squares { x: 2 } { square: (* x x) }))
(add-entry 1)
(add-entry 2)
(add-entry 3)
(add-entry 4)
(add-entry 5)

define-data-var

input: VarName, TypeDefinition, Value

output: Not Applicable

signature: (define-data-var var-name type value)

description:

define-data-var is used to define a new persisted variable for use in a smart contract. Such variable are only modifiable by the current smart contract.

Persisted variable are defined with a type and a value.

Like other kinds of definition statements, define-data-var may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).

example:

(define-data-var size int 0)
(define-private (set-size (value int))
(var-set size value))
(set-size 1)
(set-size 2)

define-fungible-token

input: TokenName, <uint>

output: Not Applicable

signature: (define-fungible-token token-name <total-supply>)

description:

define-fungible-token is used to define a new fungible token class for use in the current contract.

The second argument, if supplied, defines the total supply of the fungible token. This ensures that all calls to the ft-mint? function will never be able to create more than total-supply tokens. If any such call were to increase the total supply of tokens passed that amount, that invocation of ft-mint? will result in a runtime error and abort.

Like other kinds of definition statements, define-fungible-token may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).

Tokens defined using define-fungible-token may be used in ft-transfer?, ft-mint?, and ft-get-balance functions`

example:

(define-fungible-token stacks)
(define-fungible-token limited-supply-stacks u100)

define-non-fungible-token

input: AssetName, TypeSignature

output: Not Applicable

signature: (define-non-fungible-token asset-name asset-identifier-type)

description:

define-non-fungible-token is used to define a new non-fungible token class for use in the current contract. Individual assets are identified by their asset identifier, which must be of the type asset-identifier-type. Asset identifiers are unique identifiers.

Like other kinds of definition statements, define-non-fungible-token may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).

Assets defined using define-non-fungible-token may be used in nft-transfer?, nft-mint?, and nft-get-owner? functions`

example:

(define-non-fungible-token names (buff 50))

define-trait

input: VarName, [MethodSignature]

output: Not Applicable

signature: (define-trait trait-name ((func1-name (arg1-type arg2-type ...) (return-type))))

description:

define-trait is used to define a new trait definition for use in a smart contract. Other contracts can implement a given trait and then have their contract identifier being passed as function arguments in order to be called dynamically with contract-call?.

Traits are defined with a name, and a list functions defined with a name, a list of argument types, and return type.

Like other kinds of definition statements, define-trait may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).

example:

(define-trait token-trait
((transfer? (principal principal uint) (response uint uint))
(get-balance (principal) (response uint uint))))

use-trait

input: VarName, TraitIdentifier

output: Not Applicable

signature: (use-trait trait-alias trait-identifier)

description:

use-trait is used to bring a trait, defined in another contract, to the current contract. Subsequent references to an imported trait are signaled with the syntax <trait-alias>.

Traits import are defined with a name, used as an alias, and a trait identifier. Trait identifiers can either be using the sugared syntax (.token-a.token-trait), or be fully qualified ('SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF.token-a.token-trait).

Like other kinds of definition statements, use-trait may only be used at the top level of a smart contract definition (i.e., you cannot put such a statement in the middle of a function body).

example:

(use-trait token-a-trait 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF.token-a.token-trait)
(define-public (forward-get-balance (user principal) (contract <token-a-trait>))
(begin
(ok 1)))

impl-trait

input: TraitIdentifier

output: Not Applicable

signature: (impl-trait trait-identifier)

description:

impl-trait can be use for asserting that a contract is fully implementing a given trait. Additional checks are being performed when the contract is being published, rejecting the deployment if the contract is violating the trait specification.

Trait identifiers can either be using the sugared syntax (.token-a.token-trait), or be fully qualified ('SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF.token-a.token-trait).

Like other kinds of definition statements, impl-trait may only be used at the top level of a smart contract definition (i.e., you cannot put such a statement in the middle of a function body).

example:

(impl-trait 'SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF.token-a.token-trait)
(define-public (get-balance (account principal))
(ok u0))
(define-public (transfer? (from principal) (to principal) (amount uint))
(ok u0))