As

As is a library to convert numeric types with overflow check in Go.

Instalation

go get -u github.com/lunemec/as

Example

package main

import (
    "fmt"

    "github.com/lunemec/as"
)

func main() {
	for _, n := range []int{127, 128} {
		num, err := as.Int8(n)
		if err != nil {
			fmt.Printf("Input invalid: %d, err: %s\n", num, err)
		} else {
			fmt.Printf("Input valid: %d\n", num)
		}
	}
	// Output: Input valid: 127
	// Input invalid: -128, err: 128 (int) overflows int8
}

Example using generics

package main

import (
    "fmt"

    "github.com/lunemec/as"
)

func main() {
	for _, n := range []int{127, 128} {
		num, err := as.T[int8](n)
		if err != nil {
			fmt.Printf("Input invalid: %d, err: %s\n", num, err)
		} else {
			fmt.Printf("Input valid: %d\n", num)
		}
	}
	// Output: Input valid: 127
	// Input invalid: -128, err: 128 (int) overflows int8
}

Example slices type conversion with overflow check

package main

import (
    "fmt"

    "github.com/lunemec/as"
)

func main() {
	out, err := as.SliceT[int, int8]([]int{127, 128})
	fmt.Printf("Output: %+v, error: %+v\n", out, err)
	// Output: Output: [127 0], error: 1 error occurred:
	// 	* at index [1]: 128 (int) overflows int8
}

Other considerations

Note this checking is not free, check benchmarks for each checked cast.

There are several Go proposals to have this functionality in the language but many of them even predate this library.

There are also libraries that allow for math operations while checking for overflow at the output.

Architecture support

As currently supports these architectures and correctly handles overflows for 64/32 bit numbers:

• 386
• amd64
• arm
• arm64

It may work for s390x or ppc64le, but I have no way to test that.