zz

ch7/ch7-01.md

@@ -9,12 +9,12 @@
 package fmt
 func Fprintf(w io.Writer, format string, args ...interface{}) (int, error)
 func Printf(format string, args ...interface{}) (int, error) {
-    return Fprintf(os.Stdout, format, args...)
+	return Fprintf(os.Stdout, format, args...)
 }
 func Sprintf(format string, args ...interface{}) string {
-    var buf bytes.Buffer
-    Fprintf(&buf, format, args...)
-    return buf.String()
+	var buf bytes.Buffer
+	Fprintf(&buf, format, args...)
+	return buf.String()
 }
 ```
 Fprintf的前綴F表示文件(File)也表明格式化輸齣結果應該被寫入第一個參數提供的文件中。在Printf函數中的第一個參數os.Stdout是*os.File類型；在Sprintf函數中的第一個參數&buf是一個指向可以寫入字節的內存緩衝區，然而它
@@ -23,17 +23,17 @@ Fprintf的前綴F表示文件(File)也表明格式化輸齣結果應該被寫入
 卽使Fprintf函數中的第一個參數也不是一個文件類型。它是io.Writer類型這是一個接口類型定義如下：
 ``` go
 package io
-     // Writer is the interface that wraps the basic Write method.
-     type Writer interface {
+// Writer is the interface that wraps the basic Write method.
+type Writer interface {
+	// Write writes len(p) bytes from p to the underlying data stream.
+	// It returns the number of bytes written from p (0 <= n <= len(p))
+	// and any error encountered that caused the write to stop early.
+	// Write must return a non-nil error if it returns n < len(p).
+	// Write must not modify the slice data, even temporarily.
+	//
+	// Implementations must not retain p.
+	Write(p []byte) (n int, err error)
 }
-// Write writes len(p) bytes from p to the underlying data stream.
-// It returns the number of bytes written from p (0 <= n <= len(p))
-// and any error encountered that caused the write to stop early.
-// Write must return a non-nil error if it returns n < len(p).
-// Write must not modify the slice data, even temporarily.
-//
-// Implementations must not retain p.
-Write(p []byte) (n int, err error)
 ```
 
 io.Writer類型定義了函數Fprintf和這個函數調用者之間的約定。一方面這個約定需要調用者提供具體類型的值就像\*os.File和\*bytes.Buffer，這些類型都有一個特定籤名和行爲的Write的函數。另一方面這個約定保證了Fprintf接受任何滿足io.Writer接口的值都可以工作。Fprintf函數可能沒有假定寫入的是一個文件或是一段內存，而是寫入一個可以調用Write函數的值。