make_examples.go

Documentation: math/bits

     1  // Copyright 2017 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build ignore
     6  
     7  // This program generates example_test.go.
     8  
     9  package main
    10  
    11  import (
    12  	"bytes"
    13  	"fmt"
    14  	"log"
    15  	"math/bits"
    16  	"os"
    17  )
    18  
    19  const header = `// Copyright 2017 The Go Authors. All rights reserved.
    20  // Use of this source code is governed by a BSD-style
    21  // license that can be found in the LICENSE file.
    22  
    23  // Code generated by go run make_examples.go. DO NOT EDIT.
    24  
    25  package bits_test
    26  
    27  import (
    28  	"fmt"
    29  	"math/bits"
    30  )
    31  `
    32  
    33  func main() {
    34  	w := bytes.NewBuffer([]byte(header))
    35  
    36  	for _, e := range []struct {
    37  		name string
    38  		in   int
    39  		out  [4]any
    40  		out2 [4]any
    41  	}{
    42  		{
    43  			name: "LeadingZeros",
    44  			in:   1,
    45  			out:  [4]any{bits.LeadingZeros8(1), bits.LeadingZeros16(1), bits.LeadingZeros32(1), bits.LeadingZeros64(1)},
    46  		},
    47  		{
    48  			name: "TrailingZeros",
    49  			in:   14,
    50  			out:  [4]any{bits.TrailingZeros8(14), bits.TrailingZeros16(14), bits.TrailingZeros32(14), bits.TrailingZeros64(14)},
    51  		},
    52  		{
    53  			name: "OnesCount",
    54  			in:   14,
    55  			out:  [4]any{bits.OnesCount8(14), bits.OnesCount16(14), bits.OnesCount32(14), bits.OnesCount64(14)},
    56  		},
    57  		{
    58  			name: "RotateLeft",
    59  			in:   15,
    60  			out:  [4]any{bits.RotateLeft8(15, 2), bits.RotateLeft16(15, 2), bits.RotateLeft32(15, 2), bits.RotateLeft64(15, 2)},
    61  			out2: [4]any{bits.RotateLeft8(15, -2), bits.RotateLeft16(15, -2), bits.RotateLeft32(15, -2), bits.RotateLeft64(15, -2)},
    62  		},
    63  		{
    64  			name: "Reverse",
    65  			in:   19,
    66  			out:  [4]any{bits.Reverse8(19), bits.Reverse16(19), bits.Reverse32(19), bits.Reverse64(19)},
    67  		},
    68  		{
    69  			name: "ReverseBytes",
    70  			in:   15,
    71  			out:  [4]any{nil, bits.ReverseBytes16(15), bits.ReverseBytes32(15), bits.ReverseBytes64(15)},
    72  		},
    73  		{
    74  			name: "Len",
    75  			in:   8,
    76  			out:  [4]any{bits.Len8(8), bits.Len16(8), bits.Len32(8), bits.Len64(8)},
    77  		},
    78  	} {
    79  		for i, size := range []int{8, 16, 32, 64} {
    80  			if e.out[i] == nil {
    81  				continue // function doesn't exist
    82  			}
    83  			f := fmt.Sprintf("%s%d", e.name, size)
    84  			fmt.Fprintf(w, "\nfunc Example%s() {\n", f)
    85  			switch e.name {
    86  			case "RotateLeft", "Reverse", "ReverseBytes":
    87  				fmt.Fprintf(w, "\tfmt.Printf(\"%%0%db\\n\", %d)\n", size, e.in)
    88  				if e.name == "RotateLeft" {
    89  					fmt.Fprintf(w, "\tfmt.Printf(\"%%0%db\\n\", bits.%s(%d, 2))\n", size, f, e.in)
    90  					fmt.Fprintf(w, "\tfmt.Printf(\"%%0%db\\n\", bits.%s(%d, -2))\n", size, f, e.in)
    91  				} else {
    92  					fmt.Fprintf(w, "\tfmt.Printf(\"%%0%db\\n\", bits.%s(%d))\n", size, f, e.in)
    93  				}
    94  				fmt.Fprintf(w, "\t// Output:\n")
    95  				fmt.Fprintf(w, "\t// %0*b\n", size, e.in)
    96  				fmt.Fprintf(w, "\t// %0*b\n", size, e.out[i])
    97  				if e.name == "RotateLeft" && e.out2[i] != nil {
    98  					fmt.Fprintf(w, "\t// %0*b\n", size, e.out2[i])
    99  				}
   100  			default:
   101  				fmt.Fprintf(w, "\tfmt.Printf(\"%s(%%0%db) = %%d\\n\", %d, bits.%s(%d))\n", f, size, e.in, f, e.in)
   102  				fmt.Fprintf(w, "\t// Output:\n")
   103  				fmt.Fprintf(w, "\t// %s(%0*b) = %d\n", f, size, e.in, e.out[i])
   104  			}
   105  			fmt.Fprintf(w, "}\n")
   106  		}
   107  	}
   108  
   109  	if err := os.WriteFile("example_test.go", w.Bytes(), 0666); err != nil {
   110  		log.Fatal(err)
   111  	}
   112  }
   113
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