add floating-point precision to four decimal places

[ahaooahaz]

Fixes Or Enhances

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• [ ] Tests exist or have been written that cover this particular change.

@go-playground/validator-maintainers

[coveralls]

coverage: 74.001% (+0.01%) from 73.991% when pulling b71b5017a60fcbb4683e94e9edf559b72348c6d8 on ahaooahaz:feature/float into 5bf55dc757cad229e8297d42640ec036e2360df7 on go-playground:master.

[deankarn]

@ahaooahaz Thank you for the PR, but I already have one up that should correct the issue without truncating the decimal precision https://github.com/go-playground/validator/pull/1146

Will try to get it merged and published after work.

[ahaooahaz]

@deankarn Floating-point numbers that lose precision should be a problem caused by reflection, I think the problem appears in validator.go:77 current.Field(f.idx), if use current.Field(f.idx).Float() it already lose precision ,I saw your code modify the 32-bit and 64-bit tool functions from string to float respectively, but this is not the actual cause of the problem

[deankarn]

@ahaooahaz there is actually no problem per se.

This is a floating point precision thing and because the float32 is returned as a float64 it's actuating gaining precision.

Here's why my other PR fixes the issue without number truncation which can introduce other issues, especially where the code was implemented. The parsing code has been updated using asFloat32 and asFloat64 making it now behave identically to reflect.Float() function which both check the bit precision aka float32 vs float64

func asFloat64(param string) float64 {
    i, _ := strconv.ParseFloat(param, 64)
    return i
}

func asFloat32(param string) float64 {
    i, _ := strconv.ParseFloat(param, 32)
    return i
}

func main() {

    f32 := float32(0.1)
    f64 := float64(0.1)

    fmt.Println(float64(f32), reflect.ValueOf(f32).Float(), asFloat32("0.1"))
    fmt.Println(f64, reflect.ValueOf(f64).Float(), asFloat64("0.1"))
        //
    // output
    //
    // 0.10000000149011612 0.10000000149011612 0.10000000149011612
    // 0.1 0.1 0.1
}

[ahaooahaz]

@deankarn ohhh, I get it, GREAT WORKS!!