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Constant value

Constant value are literals or function calls that always resolve to the same value.

10, "Hello world"

Function as constant values​

A function could be treated as constant value, if they return the same value, the expression that the function invoke is constant.

warning

pub functions can't be treated as constant value when they are imported. If the function is cloned and the function could be treated as constant value, calling the cloned function will be treated as constant value in the module where it was imported.

Let as constant values​

Let is constant if all assignments and the expression are constant

//constant let
let x = 10
    y = 20
    x + y
//no constant let
let x = noConstsntFunction 10
    y = 20
    x + y

Collections as constant values​

Collection are constants if their elements are constants

//constant collection
[10, 20, 30]

//no constant collection
{(noContantFunction 10):"key"}
Note

If an if or match is constant then the expression is evaluated in compile time