...
Run Format

Source file src/strconv/fp_test.go

Documentation: strconv

     1  // Copyright 2009 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  package strconv_test
     6  
     7  import (
     8  	"bufio"
     9  	"fmt"
    10  	"os"
    11  	"strconv"
    12  	"strings"
    13  	"testing"
    14  )
    15  
    16  func pow2(i int) float64 {
    17  	switch {
    18  	case i < 0:
    19  		return 1 / pow2(-i)
    20  	case i == 0:
    21  		return 1
    22  	case i == 1:
    23  		return 2
    24  	}
    25  	return pow2(i/2) * pow2(i-i/2)
    26  }
    27  
    28  // Wrapper around strconv.ParseFloat(x, 64).  Handles dddddp+ddd (binary exponent)
    29  // itself, passes the rest on to strconv.ParseFloat.
    30  func myatof64(s string) (f float64, ok bool) {
    31  	a := strings.SplitN(s, "p", 2)
    32  	if len(a) == 2 {
    33  		n, err := strconv.ParseInt(a[0], 10, 64)
    34  		if err != nil {
    35  			return 0, false
    36  		}
    37  		e, err1 := strconv.Atoi(a[1])
    38  		if err1 != nil {
    39  			println("bad e", a[1])
    40  			return 0, false
    41  		}
    42  		v := float64(n)
    43  		// We expect that v*pow2(e) fits in a float64,
    44  		// but pow2(e) by itself may not. Be careful.
    45  		if e <= -1000 {
    46  			v *= pow2(-1000)
    47  			e += 1000
    48  			for e < 0 {
    49  				v /= 2
    50  				e++
    51  			}
    52  			return v, true
    53  		}
    54  		if e >= 1000 {
    55  			v *= pow2(1000)
    56  			e -= 1000
    57  			for e > 0 {
    58  				v *= 2
    59  				e--
    60  			}
    61  			return v, true
    62  		}
    63  		return v * pow2(e), true
    64  	}
    65  	f1, err := strconv.ParseFloat(s, 64)
    66  	if err != nil {
    67  		return 0, false
    68  	}
    69  	return f1, true
    70  }
    71  
    72  // Wrapper around strconv.ParseFloat(x, 32).  Handles dddddp+ddd (binary exponent)
    73  // itself, passes the rest on to strconv.ParseFloat.
    74  func myatof32(s string) (f float32, ok bool) {
    75  	a := strings.SplitN(s, "p", 2)
    76  	if len(a) == 2 {
    77  		n, err := strconv.Atoi(a[0])
    78  		if err != nil {
    79  			println("bad n", a[0])
    80  			return 0, false
    81  		}
    82  		e, err1 := strconv.Atoi(a[1])
    83  		if err1 != nil {
    84  			println("bad p", a[1])
    85  			return 0, false
    86  		}
    87  		return float32(float64(n) * pow2(e)), true
    88  	}
    89  	f64, err1 := strconv.ParseFloat(s, 32)
    90  	f1 := float32(f64)
    91  	if err1 != nil {
    92  		return 0, false
    93  	}
    94  	return f1, true
    95  }
    96  
    97  func TestFp(t *testing.T) {
    98  	f, err := os.Open("testdata/testfp.txt")
    99  	if err != nil {
   100  		t.Fatal("testfp: open testdata/testfp.txt:", err)
   101  	}
   102  	defer f.Close()
   103  
   104  	s := bufio.NewScanner(f)
   105  
   106  	for lineno := 1; s.Scan(); lineno++ {
   107  		line := s.Text()
   108  		if len(line) == 0 || line[0] == '#' {
   109  			continue
   110  		}
   111  		a := strings.Split(line, " ")
   112  		if len(a) != 4 {
   113  			t.Error("testdata/testfp.txt:", lineno, ": wrong field count")
   114  			continue
   115  		}
   116  		var s string
   117  		var v float64
   118  		switch a[0] {
   119  		case "float64":
   120  			var ok bool
   121  			v, ok = myatof64(a[2])
   122  			if !ok {
   123  				t.Error("testdata/testfp.txt:", lineno, ": cannot atof64 ", a[2])
   124  				continue
   125  			}
   126  			s = fmt.Sprintf(a[1], v)
   127  		case "float32":
   128  			v1, ok := myatof32(a[2])
   129  			if !ok {
   130  				t.Error("testdata/testfp.txt:", lineno, ": cannot atof32 ", a[2])
   131  				continue
   132  			}
   133  			s = fmt.Sprintf(a[1], v1)
   134  			v = float64(v1)
   135  		}
   136  		if s != a[3] {
   137  			t.Error("testdata/testfp.txt:", lineno, ": ", a[0], " ", a[1], " ", a[2], " (", v, ") ",
   138  				"want ", a[3], " got ", s)
   139  		}
   140  	}
   141  	if s.Err() != nil {
   142  		t.Fatal("testfp: read testdata/testfp.txt: ", s.Err())
   143  	}
   144  }
   145  

View as plain text