Editando: switch.go
// run // Copyright 2009 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. // Test switch statements. package main import "os" func assert(cond bool, msg string) { if !cond { print("assertion fail: ", msg, "\n") panic(1) } } func main() { i5 := 5 i7 := 7 hello := "hello" switch true { case i5 < 5: assert(false, "<") case i5 == 5: assert(true, "!") case i5 > 5: assert(false, ">") } switch { case i5 < 5: assert(false, "<") case i5 == 5: assert(true, "!") case i5 > 5: assert(false, ">") } switch x := 5; true { case i5 < x: assert(false, "<") case i5 == x: assert(true, "!") case i5 > x: assert(false, ">") } switch x := 5; true { case i5 < x: assert(false, "<") case i5 == x: assert(true, "!") case i5 > x: assert(false, ">") } switch i5 { case 0: assert(false, "0") case 1: assert(false, "1") case 2: assert(false, "2") case 3: assert(false, "3") case 4: assert(false, "4") case 5: assert(true, "5") case 6: assert(false, "6") case 7: assert(false, "7") case 8: assert(false, "8") case 9: assert(false, "9") default: assert(false, "default") } switch i5 { case 0, 1, 2, 3, 4: assert(false, "4") case 5: assert(true, "5") case 6, 7, 8, 9: assert(false, "9") default: assert(false, "default") } switch i5 { case 0: case 1: case 2: case 3: case 4: assert(false, "4") case 5: assert(true, "5") case 6: case 7: case 8: case 9: default: assert(i5 == 5, "good") } switch i5 { case 0: dummy := 0 _ = dummy fallthrough case 1: dummy := 0 _ = dummy fallthrough case 2: dummy := 0 _ = dummy fallthrough case 3: dummy := 0 _ = dummy fallthrough case 4: dummy := 0 _ = dummy assert(false, "4") case 5: dummy := 0 _ = dummy fallthrough case 6: dummy := 0 _ = dummy fallthrough case 7: dummy := 0 _ = dummy fallthrough case 8: dummy := 0 _ = dummy fallthrough case 9: dummy := 0 _ = dummy fallthrough default: dummy := 0 _ = dummy assert(i5 == 5, "good") } fired := false switch i5 { case 0: dummy := 0 _ = dummy fallthrough // tests scoping of cases case 1: dummy := 0 _ = dummy fallthrough case 2: dummy := 0 _ = dummy fallthrough case 3: dummy := 0 _ = dummy fallthrough case 4: dummy := 0 _ = dummy assert(false, "4") case 5: dummy := 0 _ = dummy fallthrough case 6: dummy := 0 _ = dummy fallthrough case 7: dummy := 0 _ = dummy fallthrough case 8: dummy := 0 _ = dummy fallthrough case 9: dummy := 0 _ = dummy fallthrough default: dummy := 0 _ = dummy fired = !fired assert(i5 == 5, "good") } assert(fired, "fired") count := 0 switch i5 { case 0: count = count + 1 fallthrough case 1: count = count + 1 fallthrough case 2: count = count + 1 fallthrough case 3: count = count + 1 fallthrough case 4: count = count + 1 assert(false, "4") case 5: count = count + 1 fallthrough case 6: count = count + 1 fallthrough case 7: count = count + 1 fallthrough case 8: count = count + 1 fallthrough case 9: count = count + 1 fallthrough default: assert(i5 == count, "good") } assert(fired, "fired") switch hello { case "wowie": assert(false, "wowie") case "hello": assert(true, "hello") case "jumpn": assert(false, "jumpn") default: assert(false, "default") } fired = false switch i := i5 + 2; i { case i7: fired = true default: assert(false, "fail") } assert(fired, "var") // switch on nil-only comparison types switch f := func() {}; f { case nil: assert(false, "f should not be nil") default: } switch m := make(map[int]int); m { case nil: assert(false, "m should not be nil") default: } switch a := make([]int, 1); a { case nil: assert(false, "m should not be nil") default: } // switch on interface. switch i := interface{}("hello"); i { case 42: assert(false, `i should be "hello"`) case "hello": assert(true, "hello") default: assert(false, `i should be "hello"`) } // switch on implicit bool converted to interface // was broken: see issue 3980 switch i := interface{}(true); { case i: assert(true, "true") case false: assert(false, "i should be true") default: assert(false, "i should be true") } // switch on interface with constant cases differing by type. // was rejected by compiler: see issue 4781 type T int type B bool type F float64 type S string switch i := interface{}(float64(1.0)); i { case nil: assert(false, "i should be float64(1.0)") case (*int)(nil): assert(false, "i should be float64(1.0)") case 1: assert(false, "i should be float64(1.0)") case T(1): assert(false, "i should be float64(1.0)") case F(1.0): assert(false, "i should be float64(1.0)") case 1.0: assert(true, "true") case "hello": assert(false, "i should be float64(1.0)") case S("hello"): assert(false, "i should be float64(1.0)") case true, B(false): assert(false, "i should be float64(1.0)") case false, B(true): assert(false, "i should be float64(1.0)") } // switch on array. switch ar := [3]int{1, 2, 3}; ar { case [3]int{1, 2, 3}: assert(true, "[1 2 3]") case [3]int{4, 5, 6}: assert(false, "ar should be [1 2 3]") default: assert(false, "ar should be [1 2 3]") } // switch on channel switch c1, c2 := make(chan int), make(chan int); c1 { case nil: assert(false, "c1 did not match itself") case c2: assert(false, "c1 did not match itself") case c1: assert(true, "chan") default: assert(false, "c1 did not match itself") } // empty switch switch { } // empty switch with default case. fired = false switch { default: fired = true } assert(fired, "fail") // Default and fallthrough. count = 0 switch { default: count++ fallthrough case false: count++ } assert(count == 2, "fail") // fallthrough to default, which is not at end. count = 0 switch i5 { case 5: count++ fallthrough default: count++ case 6: count++ } assert(count == 2, "fail") i := 0 switch x := 5; { case i < x: os.Exit(0) case i == x: case i > x: os.Exit(1) } // Unified IR converts the tag and all case values to empty // interface, when any of the case values aren't assignable to the // tag value's type. Make sure that `case nil:` compares against the // tag type's nil value (i.e., `(*int)(nil)`), not nil interface // (i.e., `any(nil)`). switch (*int)(nil) { case nil: // ok case any(nil): assert(false, "case any(nil) matched") default: assert(false, "default matched") } }
Cancelar
Kerym Chaeceran