go_pure

A static analysis tool for go-lang that ensures designated functions are pure.

Functions decorated by code>@pure</code is throw to purity check.

The norm of function purity is :

• Do not refer to mutable variables that is declared outside the function scope
• Do not call impure functions

These implies that the function always returns the same result when same arguments are passed.

Note that pure functions can have side effect, it can change the content of arguments of pointer type. It also allows print.

Example

package a

import "fmt"

// @pure
func f() {
    var gopher int32
    print(gopher)
}

var global_var int32 = 1
const global_const = 1

// @pure
func factorial(n int32) int32 {
    if n <= 0 {
        //fmt.Println("call")   // impure
        //return global_var     // impure
        return global_const     // pure
    } else {
        return n * factorial(n-1)
    }
}

// @pure
func fibonacci(n int) int {
    if n <= 0 {
        return 0;
    }

    previous := 0
    current  := 1

    for i := 1 ; i <= n ; i++ {
        next := previous + current
        previous = current
        current = next
    }
    return current
}

Install

$ go get github.com/marx-saul/go_pure/cmd/go_pure

Usage

$ go vet -vettool=`which go_pure` your-package