liquid/generics/compare.go

package generics

import (
	"reflect"
)

var (
	int64Type   = reflect.TypeOf(int64(0))
	float64Type = reflect.TypeOf(float64(0))
)

// Equal returns a bool indicating whether a == b after conversion.
func Equal(a, b interface{}) bool {
	if a == nil || b == nil {
		return a == b
	}
	ra, rb := reflect.ValueOf(a), reflect.ValueOf(b)
	switch joinKind(ra.Kind(), rb.Kind()) {
	case reflect.Array, reflect.Slice:
		if ra.Len() != rb.Len() {
			return false
		}
		for i := 0; i < ra.Len(); i++ {
			if !Equal(ra.Index(i).Interface(), rb.Index(i).Interface()) {
				return false
			}
		}
		return true
	case reflect.Bool:
		return ra.Bool() == rb.Bool()
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return ra.Convert(int64Type).Int() == rb.Convert(int64Type).Int()
	case reflect.Float32, reflect.Float64:
		return ra.Convert(float64Type).Float() == rb.Convert(float64Type).Float()
	case reflect.String:
		return ra.String() == rb.String()
	default:
		return a == b
	}
}

// Less returns a bool indicating whether a < b.
func Less(a, b interface{}) bool {
	if a == nil || b == nil {
		return false
	}
	ra, rb := reflect.ValueOf(a), reflect.ValueOf(b)
	switch joinKind(ra.Kind(), rb.Kind()) {
	case reflect.Bool:
		return !ra.Bool() && rb.Bool()
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return ra.Convert(int64Type).Int() < rb.Convert(int64Type).Int()
	case reflect.Float32, reflect.Float64:
		return ra.Convert(float64Type).Float() < rb.Convert(float64Type).Float()
	case reflect.String:
		return ra.String() < rb.String()
	default:
		return false
	}
}

func joinKind(a, b reflect.Kind) reflect.Kind {
	if a == b {
		return a
	}
	switch a {
	case reflect.Array, reflect.Slice:
		if b == reflect.Array || b == reflect.Slice {
			return reflect.Slice
		}
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		if isIntKind(b) {
			return reflect.Int64
		}
		if isFloatKind(b) {
			return reflect.Float64
		}
	case reflect.Float32, reflect.Float64:
		if isIntKind(b) || isFloatKind(b) {
			return reflect.Float64
		}
	}
	return reflect.Invalid
}

func isIntKind(k reflect.Kind) bool {
	switch k {
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return true
	default:
		return false
	}
}

func isFloatKind(k reflect.Kind) bool {
	switch k {
	case reflect.Float32, reflect.Float64:
		return true
	default:
		return false
	}
}