overflow

Check for int/int8/int16/int64/int32 integer overflow in Golang arithmetic.

Install

go get github.com/johncgriffin/overflow

Note that because Go has no template types, the majority of repetitive code is generated by overflow_template.sh. If you have to change an algorithm, change it there and regenerate the Go code via:

go generate

Synopsis

package main

import "fmt"
import "math"
import "github.com/JohnCGriffin/overflow"

func main() {

	addend := math.MaxInt64 - 5

	for i := 0; i < 10; i++ {
		sum, ok := overflow.Add(addend, i)
		fmt.Printf("%v+%v -> (%v,%v)\n",
			addend, i, sum, ok)
	}

}

yields the output

9223372036854775802+0 -> (9223372036854775802,true)
9223372036854775802+1 -> (9223372036854775803,true)
9223372036854775802+2 -> (9223372036854775804,true)
9223372036854775802+3 -> (9223372036854775805,true)
9223372036854775802+4 -> (9223372036854775806,true)
9223372036854775802+5 -> (9223372036854775807,true)
9223372036854775802+6 -> (0,false)
9223372036854775802+7 -> (0,false)
9223372036854775802+8 -> (0,false)
9223372036854775802+9 -> (0,false)

For int, int64, and int32 types, provide Add, Add32, Add64, Sub, Sub32, Sub64, etc.
Unsigned types not covered at the moment, but such additions are welcome.

Stay calm and panic

There's a good case to be made that a panic is an unidiomatic but proper response. Iff you believe that there's no valid way to continue your program after math goes wayward, you can use the easier Addp, Mulp, Subp, and Divp versions which return the normal result or panic.