good good study, day day up!

vendor/gopl.io/ch12/format/format.go

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+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 332.
+
+// Package format provides an Any function that can format any value.
+//!+
+package format
+
+import (
+	"reflect"
+	"strconv"
+)
+
+// Any formats any value as a string.
+func Any(value interface{}) string {
+	return formatAtom(reflect.ValueOf(value))
+}
+
+// formatAtom formats a value without inspecting its internal structure.
+func formatAtom(v reflect.Value) string {
+	switch v.Kind() {
+	case reflect.Invalid:
+		return "invalid"
+	case reflect.Int, reflect.Int8, reflect.Int16,
+		reflect.Int32, reflect.Int64:
+		return strconv.FormatInt(v.Int(), 10)
+	case reflect.Uint, reflect.Uint8, reflect.Uint16,
+		reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return strconv.FormatUint(v.Uint(), 10)
+	// ...floating-point and complex cases omitted for brevity...
+	case reflect.Bool:
+		return strconv.FormatBool(v.Bool())
+	case reflect.String:
+		return strconv.Quote(v.String())
+	case reflect.Chan, reflect.Func, reflect.Ptr, reflect.Slice, reflect.Map:
+		return v.Type().String() + " 0x" +
+			strconv.FormatUint(uint64(v.Pointer()), 16)
+	default: // reflect.Array, reflect.Struct, reflect.Interface
+		return v.Type().String() + " value"
+	}
+}
+
+//!-

vendor/gopl.io/ch12/format/format_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 format_test
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	"gopl.io/ch12/format"
+)
+
+func Test(t *testing.T) {
+	// The pointer values are just examples, and may vary from run to run.
+	//!+time
+	var x int64 = 1
+	var d time.Duration = 1 * time.Nanosecond
+	fmt.Println(format.Any(x))                  // "1"
+	fmt.Println(format.Any(d))                  // "1"
+	fmt.Println(format.Any([]int64{x}))         // "[]int64 0x8202b87b0"
+	fmt.Println(format.Any([]time.Duration{d})) // "[]time.Duration 0x8202b87e0"
+	//!-time
+}