gopl-zh.github.com/vendor/gopl.io/ch12/display/display_test.go

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// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
package display
import (
"io"
"net"
"os"
"reflect"
"sync"
"testing"
"gopl.io/ch7/eval"
)
// NOTE: we can't use !+..!- comments to excerpt these tests
// into the book because it defeats the Example mechanism,
// which requires the // Output comment to be at the end
// of the function.
func Example_expr() {
e, _ := eval.Parse("sqrt(A / pi)")
Display("e", e)
// Output:
// Display e (eval.call):
// e.fn = "sqrt"
// e.args[0].type = eval.binary
// e.args[0].value.op = 47
// e.args[0].value.x.type = eval.Var
// e.args[0].value.x.value = "A"
// e.args[0].value.y.type = eval.Var
// e.args[0].value.y.value = "pi"
}
func Example_slice() {
Display("slice", []*int{new(int), nil})
// Output:
// Display slice ([]*int):
// (*slice[0]) = 0
// slice[1] = nil
}
func Example_nilInterface() {
var w io.Writer
Display("w", w)
// Output:
// Display w (<nil>):
// w = invalid
}
func Example_ptrToInterface() {
var w io.Writer
Display("&w", &w)
// Output:
// Display &w (*io.Writer):
// (*&w) = nil
}
func Example_struct() {
Display("x", struct{ x interface{} }{3})
// Output:
// Display x (struct { x interface {} }):
// x.x.type = int
// x.x.value = 3
}
func Example_interface() {
var i interface{} = 3
Display("i", i)
// Output:
// Display i (int):
// i = 3
}
func Example_ptrToInterface2() {
var i interface{} = 3
Display("&i", &i)
// Output:
// Display &i (*interface {}):
// (*&i).type = int
// (*&i).value = 3
}
func Example_array() {
Display("x", [1]interface{}{3})
// Output:
// Display x ([1]interface {}):
// x[0].type = int
// x[0].value = 3
}
func Example_movie() {
//!+movie
type Movie struct {
Title, Subtitle string
Year int
Color bool
Actor map[string]string
Oscars []string
Sequel *string
}
//!-movie
//!+strangelove
strangelove := Movie{
Title: "Dr. Strangelove",
Subtitle: "How I Learned to Stop Worrying and Love the Bomb",
Year: 1964,
Color: false,
Actor: map[string]string{
"Dr. Strangelove": "Peter Sellers",
"Grp. Capt. Lionel Mandrake": "Peter Sellers",
"Pres. Merkin Muffley": "Peter Sellers",
"Gen. Buck Turgidson": "George C. Scott",
"Brig. Gen. Jack D. Ripper": "Sterling Hayden",
`Maj. T.J. "King" Kong`: "Slim Pickens",
},
Oscars: []string{
"Best Actor (Nomin.)",
"Best Adapted Screenplay (Nomin.)",
"Best Director (Nomin.)",
"Best Picture (Nomin.)",
},
}
//!-strangelove
Display("strangelove", strangelove)
// We don't use an Output: comment since displaying
// a map is nondeterministic.
/*
//!+output
Display strangelove (display.Movie):
strangelove.Title = "Dr. Strangelove"
strangelove.Subtitle = "How I Learned to Stop Worrying and Love the Bomb"
strangelove.Year = 1964
strangelove.Color = false
strangelove.Actor["Gen. Buck Turgidson"] = "George C. Scott"
strangelove.Actor["Brig. Gen. Jack D. Ripper"] = "Sterling Hayden"
strangelove.Actor["Maj. T.J. \"King\" Kong"] = "Slim Pickens"
strangelove.Actor["Dr. Strangelove"] = "Peter Sellers"
strangelove.Actor["Grp. Capt. Lionel Mandrake"] = "Peter Sellers"
strangelove.Actor["Pres. Merkin Muffley"] = "Peter Sellers"
strangelove.Oscars[0] = "Best Actor (Nomin.)"
strangelove.Oscars[1] = "Best Adapted Screenplay (Nomin.)"
strangelove.Oscars[2] = "Best Director (Nomin.)"
strangelove.Oscars[3] = "Best Picture (Nomin.)"
strangelove.Sequel = nil
//!-output
*/
}
// This test ensures that the program terminates without crashing.
func Test(t *testing.T) {
// Some other values (YMMV)
Display("os.Stderr", os.Stderr)
// Output:
// Display os.Stderr (*os.File):
// (*(*os.Stderr).file).fd = 2
// (*(*os.Stderr).file).name = "/dev/stderr"
// (*(*os.Stderr).file).nepipe = 0
var w io.Writer = os.Stderr
Display("&w", &w)
// Output:
// Display &w (*io.Writer):
// (*&w).type = *os.File
// (*(*(*&w).value).file).fd = 2
// (*(*(*&w).value).file).name = "/dev/stderr"
// (*(*(*&w).value).file).nepipe = 0
var locker sync.Locker = new(sync.Mutex)
Display("(&locker)", &locker)
// Output:
// Display (&locker) (*sync.Locker):
// (*(&locker)).type = *sync.Mutex
// (*(*(&locker)).value).state = 0
// (*(*(&locker)).value).sema = 0
Display("locker", locker)
// Output:
// Display locker (*sync.Mutex):
// (*locker).state = 0
// (*locker).sema = 0
// (*(&locker)) = nil
locker = nil
Display("(&locker)", &locker)
// Output:
// Display (&locker) (*sync.Locker):
// (*(&locker)) = nil
ips, _ := net.LookupHost("golang.org")
Display("ips", ips)
// Output:
// Display ips ([]string):
// ips[0] = "173.194.68.141"
// ips[1] = "2607:f8b0:400d:c06::8d"
// Even metarecursion! (YMMV)
Display("rV", reflect.ValueOf(os.Stderr))
// Output:
// Display rV (reflect.Value):
// (*rV.typ).size = 8
// (*rV.typ).ptrdata = 8
// (*rV.typ).hash = 871609668
// (*rV.typ)._ = 0
// ...
// a pointer that points to itself
type P *P
var p P
p = &p
if false {
Display("p", p)
// Output:
// Display p (display.P):
// ...stuck, no output...
}
// a map that contains itself
type M map[string]M
m := make(M)
m[""] = m
if false {
Display("m", m)
// Output:
// Display m (display.M):
// ...stuck, no output...
}
// a slice that contains itself
type S []S
s := make(S, 1)
s[0] = s
if false {
Display("s", s)
// Output:
// Display s (display.S):
// ...stuck, no output...
}
// a linked list that eats its own tail
type Cycle struct {
Value int
Tail *Cycle
}
var c Cycle
c = Cycle{42, &c}
if false {
Display("c", c)
// Output:
// Display c (display.Cycle):
// c.Value = 42
// (*c.Tail).Value = 42
// (*(*c.Tail).Tail).Value = 42
// ...ad infinitum...
}
}