Functions and their types

Functions in Tact could be defined in different ways:

• Global static function
• Extension functions
• Mutable functions
• Native functions
• Receiver functions
• Getter functions

Global static functions

You can define global function anywhere in you program:

fun pow(a: Int, c: Int): Int {
  let res: Int = a;
  repeat(c) {
    res = res * a;
  }
  return res;
}

Extension function

Extension functions allows you to implement extension for any possible type.

Warning Name of the first argument MUST be named self and type of this argument is the type you are extending.

extends fun pow(self: Int, c: Int) {
  let res: Int = a;
  repeat(c) {
    res = res * a;
  }
  return res;
}

Mutable functions

Mutable functions are performing mutation of a value replacing it with an execution result. To perform mutation function must change self value.

extends mutates fun pow(self: Int, c: Int) {
  let res: Int = a;
  repeat(c) {
    res = res * a;
  }
  self = res;
}

Native functions

Native functions are direct binding to a func functions:

Note Native functions could be also mutable and extension one

@name(store_uint)
native storeUint(s: Builder, value: Int, bits: Int): Builder;
 
@name(load_int)
extends mutates native loadInt(self: Slice, l: Int): Int;

Receiver functions

Receiver functions are special function that are responsible of receiving messages in contracts and could be defined only within a contract or trait.

contract Treasure {
 
  // ...
  
  // This means that this contract can receive comment "Increment" and this function would be called for such messages
  receive("Increment") {
    self.counter = self.counter + 1;
  }
}

Getter Functions

Getter functions that defines getters on smart contract and can be defined only within a contract or trait.

contract Treasure {
 
  // ...
  
  get fun counter(): Int {
    return self.counter;
  }
}