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one.go
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one.go
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// Copyright (c) 2021 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package curry
import (
"fmt"
"reflect"
)
// One wraps the given function to require one less argument, passing in the
// given value instead. The value MUST NOT be nil.
//
// BUG(abg): Variadic functions are not supported.
func One(f interface{}, a interface{}) interface{} {
if f == nil {
panic("f is required")
}
if a == nil {
panic("a is required and cannot be nil")
}
fType := reflect.TypeOf(f)
if fType.Kind() != reflect.Func {
panic(fmt.Sprintf("%v (%v) is not a function", f, fType))
}
if fType.IsVariadic() {
panic(fmt.Sprintf("%v (%v) is variadic", f, fType))
}
in := args(fType)
out := returns(fType)
if len(in) == 0 {
panic(fmt.Sprintf("%v (%v) does not accept enough arguments to curry in %v", f, fType, a))
}
fVal := reflect.ValueOf(f)
aVal := reflect.ValueOf(a)
newFType := reflect.FuncOf(in[1:], out, false)
return reflect.MakeFunc(newFType, func(args []reflect.Value) []reflect.Value {
newArgs := make([]reflect.Value, 0, fType.NumIn())
newArgs = append(newArgs, aVal)
newArgs = append(newArgs, args...)
return fVal.Call(newArgs)
}).Interface()
}
func args(f reflect.Type) []reflect.Type {
in := make([]reflect.Type, f.NumIn())
for i := 0; i < f.NumIn(); i++ {
in[i] = f.In(i)
}
return in
}
func returns(f reflect.Type) []reflect.Type {
out := make([]reflect.Type, f.NumOut())
for i := 0; i < f.NumOut(); i++ {
out[i] = f.Out(i)
}
return out
}