83 lines
2.1 KiB
Go
83 lines
2.1 KiB
Go
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package main
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import (
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"fmt"
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"os"
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)
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type point struct {
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x, y int
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}
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// common string formatting tasks
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func main() {
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// prints an instance of point struct
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p := point{1, 2}
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fmt.Printf("struct1: %v\n", p)
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// the %+v variant will include the struct’s field names
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fmt.Printf("struct2: %+v\n", p)
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// the %#v variant prints a Go syntax representation of the value
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fmt.Printf("struct3: %#v\n", p)
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// the %T variant prints the type of a value
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fmt.Printf("type: %T\n", p)
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// formatting booleans straight-forward
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fmt.Printf("bool: %t\n", true)
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// use %d for standard, base-10 formatting
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fmt.Printf("int: %d\n", 123)
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// prints a binary representation
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fmt.Printf("bin: %b\n", 14)
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// prints the character corresponding to the given integer
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fmt.Printf("char: %c\n", 33)
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// %x provides hex encoding
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fmt.Printf("hex: %x\n", 456)
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// decimal formatting use %f
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fmt.Printf("float1: %f\n", 78.9)
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// %e and %E format the float in (different versions of) scientific notation
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fmt.Printf("float2: %e\n", 123400000.0)
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fmt.Printf("float3: %E\n", 123400000.0)
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// basic string printing use %s
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fmt.Printf("str1: %s\n", "\"string\"")
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// to double-quote strings use %q
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fmt.Printf("str2: %q\n", "\"string\"")
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// %x renders the string in base-16, with two output characters per byte of input
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fmt.Printf("str3: %x\n", "hex this")
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// use %p to print a representation of a pointer
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fmt.Printf("pointer: %p\n", &p)
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// to specify the width of an integer, use a number after the % in the verb
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fmt.Printf("width1: |%6d|%6d|\n", 12, 345)
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// to specify the width of printed floats
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fmt.Printf("width2: |%6.2f|%6.2f|\n", 1.2, 3.45)
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// to left-justify, use the - flag
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fmt.Printf("width3: |%-6.2f|%-6.2f|\n", 1.2, 3.45)
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// specify width when formatting strings
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fmt.Printf("width4: |%6s|%6s|\n", "foo", "b")
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// and left-justify strings with - too
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fmt.Printf("width5: |%-6s|%-6s|\n", "foo", "b")
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// Sprintf formats and returns a string without printing it anywhere
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s := fmt.Sprintf("sprintf: a %s", "string")
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fmt.Println(s)
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// format+print to io.Writers other than os.Stdout using Fprintf
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fmt.Fprintf(os.Stderr, "io: an %s\n", "error")
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}
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