fp-go/v2/function/generic/switch.go

// Copyright (c) 2023 - 2025 IBM Corp.
// All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package generic

// Switch applies a handler to different cases. The handers are stored in a map. A key function
// extracts the case from a value.
func Switch[HF ~func(T) R, N ~map[K]HF, KF ~func(T) K, K comparable, T, R any](kf KF, n N, d HF) HF {
	return func(t T) R {
		f, ok := n[kf(t)]
		if ok {
			return f(t)
		}
		return d(t)
	}
}