publish string-formatting

examples.txt

@@ -44,7 +44,7 @@ Defer
 # Recover
 Collection Functions
 String Functions
-# String Formatting
+String Formatting
 Regular Expressions
 # Bytes
 # JSON

examples/string-formatting/string-formatting.go

@@ -1,20 +1,110 @@
+// Go offers excellent support for string formatting in
+// the `printf` tradition. Here are some examples of
+// common string formatting tasks.
+
 package main
 
 import "fmt"
+import "os"
 
-type Point struct {
+type point struct {
     x, y int
 }
 
 func main() {
-    point := Point{1, 2}
 
-    fmt.Printf("default: %v\n", point)
-    fmt.Printf("default w/ vals: %+v\n", point)
-    fmt.Printf("go: %#v\n", point)
-    fmt.Printf("go type: %T\n", point)
+    // Go offers several printing "verbs" designed to
+    // format general Go values. For example, this prints
+    // an instance of our `point` struct.
+    p := point{1, 2}
+    fmt.Printf("%v \n", p)
 
-    fmt.Printf("boolean: %t\n", true)
+    // If the value is a struct, the `%+v` variant will
+    // include the struct's field names.
+    fmt.Printf("%+v \n", p)
+
+    // The `%#v` variant prints a Go syntax representation
+    // of the value, i.e. the source code snippet that
+    // would produce that value.
+    fmt.Printf("%#v \n", p)
+
+    // To print the type of a value, use `%T`.
+    fmt.Printf("%T \n", p)
+
+    // Formatting booleans is straight-forward.
+    fmt.Printf("%t \n", true)
+
+    // There are many options for formatting integers.
+    // Use `%d` for standard, base-10 formatting.
+    fmt.Printf("%d \n", 123)
+
+    // This prints a binary representation.
+    fmt.Printf("%b \n", 14)
+
+    // This prints the character corresponding to the
+    // given integer.
+    fmt.Printf("%c \n", 33)
+
+    // `%x` provides hex encoding.
+    fmt.Printf("%x \n", 456)
+
+    // There are also several formatting options for
+    // floats. For basic decimal formatting use `%f`.
+    fmt.Printf("%f", 78.9)
+
+    // `%e` and `%E` format the float in (slightly
+    // different versions of) scientific notation.
+    fmt.Printf("%e \n", 123400000.0)
+    fmt.Printf("%E \n", 123400000.0)
+
+    // For basic string printing use `%s`.
+    fmt.Printf("%s \n", "\"string\"")
+
+    // To double-quote strings as in Go source, use `%q`.
+    fmt.Printf("%q \n", "\"string\"")
+
+    // As with integers as seen earlier, `%x` renders
+    // the string in base-16, with two output characters
+    // per byte of input.
+    fmt.Printf("%x \n", "hex this")
+
+    // To print a representation of a pointer, use `%p`.
+    fmt.Printf("%p \n", &p)
+
+    // When formatting numbers you will often want to
+    // control the width and precision of the resulting
+    // figure. To specify the width of an integer, use a
+    // number after the `%` in the verb. By default the
+    // result will be right-justified and padded with
+    // spaces.
+    fmt.Printf("|%6d|%6d| \n", 12, 345)
+
+    // You can also specify the width of printed floats,
+    // though usually you'll also want to restrict the
+    // decimal precision at the same time with the
+    // width.precision syntax.
+    fmt.Printf("|%6.2f|%6.2f| \n", 1.2, 3.45)
+
+    // To left-justify, use the `-` flag.
+    fmt.Printf("|%-6.2f|%-6.2f| \n", 1.2, 3.45)
+
+    // You may also want to control width when formatting
+    // strings, especially to ensure that they align in
+    // table-like output. For basic right-justified width.
+    fmt.Printf("|%6s|%6s|\n", "foo", "b")
+
+    // To left-justify use the `-` flag as with numbers.
+    fmt.Printf("|%-6s|%-6s|\n", "foo", "b")
+
+    // So far we've seen `Printf`, which prints the
+    // formatted string to `os.Stdout`. `Sprintf` formats
+    // and returns a string without printing it anywhere.
+    s := fmt.Sprintf("a %s ", "string")
+    fmt.Println(s)
+
+    // You can format+print to `io.Writers` other than
+    // `os.Stdout` using `Fprintf`.
+    fmt.Fprintf(os.Stderr, "an %s \n", "error")
 }
 
-// todo: the rest
+// todo: #golang has excellent support for string formatting in the classic printf tradition: https://gobyexample.com/string-formatting.

examples/string-formatting/string-formatting.sh

@@ -1,6 +1,23 @@
 $ go run string-formatting.go 
-default: {1 2}
-default w/ vals: {x:1 y:2}
-go: main.Point{x:1, y:2}
-go type: main.Point
-boolean: true
+{1 2} 
+{x:1 y:2} 
+main.point{x:1, y:2} 
+main.point 
+true 
+123 
+1110 
+! 
+1c8 
+78.9000001.234000e+08 
+1.234000E+08 
+"string" 
+"\"string\"" 
+6865782074686973 
+0x42134100 
+|    12|   345| 
+|  1.20|  3.45| 
+|1.20  |3.45  | 
+|   foo|     b|
+|foo   |b     |
+a string 
+an error