expr

expr/expr.go

@@ -1,9 +1,128 @@
 package expr
 
 // 如为真返回参数一，否则返回参数二
-func If[T any](e bool, v1, v2 T) T {
+func Ternary[T any](e bool, v1, v2 T) T {
 	if e {
 		return v1
 	}
 	return v2
 }
+
+func TernaryF[T any](condition bool, ifFunc func() T, elseFunc func() T) T {
+	if condition {
+		return ifFunc()
+	}
+
+	return elseFunc()
+}
+
+type ifElse[T any] struct {
+	result T
+	done   bool
+}
+
+func If[T any](condition bool, result T) *ifElse[T] {
+	if condition {
+		return &ifElse[T]{result, true}
+	}
+
+	var t T
+	return &ifElse[T]{t, false}
+}
+
+func IfF[T any](condition bool, resultF func() T) *ifElse[T] {
+	if condition {
+		return &ifElse[T]{resultF(), true}
+	}
+
+	var t T
+	return &ifElse[T]{t, false}
+}
+
+func (i *ifElse[T]) ElseIf(condition bool, result T) *ifElse[T] {
+	if !i.done && condition {
+		i.result = result
+		i.done = true
+	}
+
+	return i
+}
+
+func (i *ifElse[T]) ElseIfF(condition bool, resultF func() T) *ifElse[T] {
+	if !i.done && condition {
+		i.result = resultF()
+		i.done = true
+	}
+
+	return i
+}
+
+func (i *ifElse[T]) Else(result T) T {
+	if i.done {
+		return i.result
+	}
+
+	return result
+}
+
+func (i *ifElse[T]) ElseF(resultF func() T) T {
+	if i.done {
+		return i.result
+	}
+
+	return resultF()
+}
+
+type switchCase[T comparable, R any] struct {
+	predicate T
+	result    R
+	done      bool
+}
+
+func Switch[T comparable, R any](predicate T) *switchCase[T, R] {
+	var result R
+
+	return &switchCase[T, R]{
+		predicate,
+		result,
+		false,
+	}
+}
+
+func SwitchF[T comparable, R any](predicate func() T) *switchCase[T, R] {
+	return Switch[T, R](predicate())
+}
+
+func (s *switchCase[T, R]) Case(val T, result R) *switchCase[T, R] {
+	if !s.done && s.predicate == val {
+		s.result = result
+		s.done = true
+	}
+
+	return s
+}
+
+func (s *switchCase[T, R]) CaseF(val T, cb func() R) *switchCase[T, R] {
+	if !s.done && s.predicate == val {
+		s.result = cb()
+		s.done = true
+	}
+
+	return s
+}
+
+func (s *switchCase[T, R]) Default(result R) R {
+	if !s.done {
+		s.result = result
+	}
+
+	return s.result
+}
+
+func (s *switchCase[T, R]) DefaultF(cb func() R) R {
+	if !s.done {
+		s.result = cb()
+	}
+
+	return s.result
+}

expr/expr_test.go

@@ -1,9 +1,31 @@
 package expr
 
-import "testing"
+import (
+	"testing"
 
-func TestIf(t *testing.T) {
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTernary(t *testing.T) {
 	v1 := 10
 	v2 := 4
-	t.Log(If(v1 > v2, v1, v2))
+	t.Log(Ternary(v1 > v2, v1, v2))
+}
+
+func TestIf(t *testing.T) {
+	is := assert.New(t)
+
+	is.Equal(1, If(true, 1).ElseIf(false, 2).Else(3))
+	is.Equal(1, If(true, 1).ElseIf(true, 2).Else(3))
+	is.Equal(2, If(false, 1).ElseIf(true, 2).Else(3))
+	is.Equal(3, If(false, 1).ElseIf(false, 2).Else(3))
+}
+
+func TestSwitch(t *testing.T) {
+	is := assert.New(t)
+
+	is.Equal(1, Switch[int, int](42).Case(42, 1).Case(1, 2).Default(3))
+	is.Equal(1, Switch[int, int](42).Case(42, 1).Case(42, 2).Default(3))
+	is.Equal(1, Switch[int, int](42).Case(1, 1).Case(42, 2).Default(3))
+	is.Equal(1, Switch[int, int](42).Case(1, 1).Case(1, 2).Default(3))
 }