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1 /*******************************************************************************
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2
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3 copyright: Copyright (c) 2004 Kris Bell. All rights reserved
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4
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5 license: BSD style: $(LICENSE)
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6
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7 version: Initial release: Nov 2005
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8
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9 author: Kris
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10
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11 A set of functions for converting between string and floating-
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12 point values.
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13
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14 Applying the D "import alias" mechanism to this module is highly
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15 recommended, in order to limit namespace pollution:
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16 ---
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17 import Float = tango.text.convert.Float;
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18
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19 auto f = Float.parse ("3.14159");
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20 ---
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21
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22 *******************************************************************************/
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23
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24 module tango.text.convert.Float;
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25
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26 private import tango.core.Exception;
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27
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28 private import Integer = tango.text.convert.Integer;
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29
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30 private alias real NumType;
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31
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32 private extern (C) NumType log10l(NumType x);
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33
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34 /******************************************************************************
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35
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36 Constants
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37
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38 ******************************************************************************/
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39
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40 private enum
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41 {
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42 Dec = 2, // default decimal places
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43 Exp = 10, // default switch to scientific notation
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44 }
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45
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46 /******************************************************************************
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47
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48 Convert a formatted string of digits to a floating-point
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49 number. Throws an exception where the input text is not
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50 parsable in its entirety.
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51
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52 ******************************************************************************/
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53
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54 NumType toFloat(T) (T[] src)
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55 {
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56 uint len;
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57
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58 auto x = parse (src, &len);
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59 if (len < src.length)
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60 throw new IllegalArgumentException ("Float.toFloat :: invalid number");
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61 return x;
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62 }
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63
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64 /******************************************************************************
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65
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66 Template wrapper to make life simpler. Returns a text version
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67 of the provided value.
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68
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69 See format() for details
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70
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71 ******************************************************************************/
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72
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73 char[] toString (NumType d, uint decimals=Dec, int e=Exp)
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74 {
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75 char[64] tmp = void;
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76
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77 return format (tmp, d, decimals, e).dup;
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78 }
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79
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80 /******************************************************************************
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81
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82 Template wrapper to make life simpler. Returns a text version
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83 of the provided value.
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84
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85 See format() for details
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86
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87 ******************************************************************************/
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88
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89 wchar[] toString16 (NumType d, uint decimals=Dec, int e=Exp)
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90 {
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91 wchar[64] tmp = void;
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92
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93 return format (tmp, d, decimals, e).dup;
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94 }
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95
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96 /******************************************************************************
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97
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98 Template wrapper to make life simpler. Returns a text version
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99 of the provided value.
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100
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101 See format() for details
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102
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103 ******************************************************************************/
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104
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105 dchar[] toString32 (NumType d, uint decimals=Dec, int e=Exp)
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106 {
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107 dchar[64] tmp = void;
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108
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109 return format (tmp, d, decimals, e).dup;
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110 }
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111
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112 /******************************************************************************
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113
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114 Convert a float to a string. This produces pretty good results
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115 for the most part, though one should use David Gay's dtoa package
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116 for best accuracy.
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117
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118 Note that the approach first normalizes a base10 mantissa, then
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119 pulls digits from the left side whilst emitting them (rightward)
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120 to the output.
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121
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122 The e parameter controls the number of exponent places emitted,
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123 and can thus control where the output switches to the scientific
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124 notation. For example, setting e=2 for 0.01 or 10.0 would result
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125 in normal output. Whereas setting e=1 would result in both those
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126 values being rendered in scientific notation instead. Setting e
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127 to 0 forces that notation on for everything.
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128
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129 TODO: this should be replaced, as it is not sufficiently accurate
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130
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131 ******************************************************************************/
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132
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133 T[] format(T, D=double, U=uint) (T[] dst, D x, U decimals=Dec, int e=Exp)
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134 {return format!(T)(dst, x, decimals, e);}
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135
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136 T[] format(T) (T[] dst, NumType x, uint decimals=Dec, int e=Exp)
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137 {
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138 static T[] inf = "-inf";
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139 static T[] nan = "-nan";
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140
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141 // extract the sign bit
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142 static bool signed (NumType x)
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143 {
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144 static if (NumType.sizeof is 4)
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145 return ((*cast(uint *)&x) & 0x8000_0000) != 0;
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146
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147 static if (NumType.sizeof is 8)
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148 return ((*cast(ulong *)&x) & 0x8000_0000_0000_0000) != 0;
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149 else
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150 {
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151 auto pe = cast(ubyte *)&x;
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152 return (pe[9] & 0x80) != 0;
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153 }
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154 }
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155
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156 // strip digits from the left of a normalized base-10 number
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157 static int toDigit (inout NumType v, inout int count)
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158 {
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159 int digit;
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160
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161 // Don't exceed max digits storable in a real
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162 // (-1 because the last digit is not always storable)
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163 if (--count <= 0)
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164 digit = 0;
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165 else
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166 {
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167 // remove leading digit, and bump
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168 digit = cast(int) v;
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169 v = (v - digit) * 10.0;
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170 }
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171 return digit + '0';
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172 }
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173
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174 // extract the sign
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175 bool sign = signed (x);
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176 if (sign)
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177 x = -x;
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178
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179 if (x !<>= x)
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180 return sign ? nan : nan[1..$];
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181
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182 if (x is x.infinity)
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183 return sign ? inf : inf[1..$];
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184
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185 // assume no exponent
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186 int exp = 0;
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187
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188 // don't scale if zero
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189 if (x > 0.0)
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190 {
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191 // extract base10 exponent
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192 exp = cast(int) log10l (x);
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193
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194 // round up a bit
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195 auto d = decimals;
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196 if (exp < 0)
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197 d -= exp;
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198 x += 0.5 / pow10 (d);
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199
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200 // extract base10 exponent
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201 exp = cast(int) log10l (x);
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202
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203 // normalize base10 mantissa (0 < m < 10)
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204 int len = exp;
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205 if (exp < 0)
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206 x *= pow10 (len = -exp);
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207 else
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208 x /= pow10 (exp);
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209
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210 // switch to short display if not enough space
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211 if (len >= e)
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212 e = 0;
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213 }
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214
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215 T* p = dst.ptr;
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216 int count = NumType.dig;
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217
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218 // emit sign
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219 if (sign)
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220 *p++ = '-';
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221
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222 // are we doing +/-exp format?
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223 if (e is 0)
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224 {
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225 assert (dst.length > decimals + 7);
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226
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227 // emit first digit, and decimal point
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228 *p++ = toDigit (x, count);
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229 if (decimals)
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230 {
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231 *p++ = '.';
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232 if (exp < 0)
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233 count += exp;
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234 }
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235
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236 // emit rest of mantissa
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237 while (decimals-- > 0)
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238 *p++ = toDigit (x, count);
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239
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240 // emit exponent, if non zero
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241 if (exp)
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242 {
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243 *p++ = 'e';
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244 *p++ = (exp < 0) ? '-' : '+';
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245 if (exp < 0)
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246 exp = -exp;
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247
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248 if (exp >= 100)
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249 {
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250 *p++ = (exp/100) + '0';
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251 exp %= 100;
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252 }
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253
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254 *p++ = (exp/10) + '0';
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255 *p++ = (exp%10) + '0';
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256 }
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257 }
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258 else
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259 {
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260 assert (dst.length >= (((exp < 0) ? 0 : exp) + decimals + 1));
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261
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262 // if fraction only, emit a leading zero
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263 if (exp < 0)
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264 *p++ = '0';
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265 else
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266 // emit all digits to the left of point
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267 for (; exp >= 0; --exp)
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268 *p++ = toDigit (x, count);
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269
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270 // emit point
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271 if (decimals)
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272 *p++ = '.';
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273
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274 // emit leading fractional zeros?
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275 for (++exp; exp < 0 && decimals > 0; --decimals, ++exp)
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276 *p++ = '0';
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277
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278 // output remaining digits, if any. Trailing
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279 // zeros are also returned from toDigit()
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280 while (decimals-- > 0)
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281 *p++ = toDigit (x, count);
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282 }
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283
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284 return dst [0..(p - dst.ptr)];
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285 }
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286
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287
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288 /******************************************************************************
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289
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290 Convert a formatted string of digits to a floating-point number.
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291 Good for general use, but use David Gay's dtoa package if serious
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292 rounding adjustments should be applied.
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293
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294 ******************************************************************************/
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295
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296 NumType parse(T) (T[] src, uint* ate=null)
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297 {
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298 T c;
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299 T* p;
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300 int exp;
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301 bool sign;
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302 uint radix;
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303 NumType value = 0.0;
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304
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305 // remove leading space, and sign
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306 c = *(p = src.ptr + Integer.trim (src, sign, radix));
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307
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308 // handle non-decimal representations
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309 if (radix != 10)
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310 {
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311 long v = Integer.parse (src, radix, ate);
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312 return *cast(NumType*) &v;
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313 }
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314
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315 // set begin and end checks
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316 auto begin = p;
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317 auto end = src.ptr + src.length;
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318
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319 // read leading digits; note that leading
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320 // zeros are simply multiplied away
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321 while (c >= '0' && c <= '9' && p < end)
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322 {
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323 value = value * 10 + (c - '0');
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324 c = *++p;
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325 }
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326
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327 // gobble up the point
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328 if (c is '.' && p < end)
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329 c = *++p;
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330
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331 // read fractional digits; note that we accumulate
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332 // all digits ... very long numbers impact accuracy
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333 // to a degree, but perhaps not as much as one might
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334 // expect. A prior version limited the digit count,
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335 // but did not show marked improvement. For maximum
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336 // accuracy when reading and writing, use David Gay's
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337 // dtoa package instead
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338 while (c >= '0' && c <= '9' && p < end)
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339 {
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340 value = value * 10 + (c - '0');
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341 c = *++p;
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342 --exp;
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343 }
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344
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345 // did we get something?
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346 if (value)
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347 {
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348 // parse base10 exponent?
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349 if ((c is 'e' || c is 'E') && p < end )
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350 {
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351 uint eaten;
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352 exp += Integer.parse (src[(++p-src.ptr) .. $], 0, &eaten);
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353 p += eaten;
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354 }
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355
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356 // adjust mantissa; note that the exponent has
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357 // already been adjusted for fractional digits
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358 if (exp < 0)
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359 value /= pow10 (-exp);
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360 else
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361 value *= pow10 (exp);
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362 }
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363 else
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364 // was it was nan instead?
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365 if (p is begin)
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366 if (p[0..3] == "inf")
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367 p += 3, value = value.infinity;
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368 else
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369 if (p[0..3] == "nan")
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370 p += 3, value = value.nan;
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371
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372 // set parse length, and return value
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373 if (ate)
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374 *ate = p - src.ptr;
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375
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376 if (sign)
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377 value = -value;
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378 return value;
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379 }
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380
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381 /******************************************************************************
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382
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383 Truncate trailing '0' and '.' from a string, such that 200.000
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384 becomes 200, and 20.10 becomes 20.1
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385
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386 Returns a potentially shorter slice of what you give it.
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387
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388 ******************************************************************************/
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389
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390 T[] truncate(T) (T[] s)
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391 {
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392 auto tmp = s;
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393 auto i = tmp.length;
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394 foreach (idx, c; tmp)
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395 if (c is '.')
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396 while (--i >= idx)
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397 if (tmp[i] != '0')
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398 {
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399 if (tmp[i] is '.')
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400 --i;
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401 s = tmp [0 .. i+1];
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402 while (--i >= idx)
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403 if (tmp[i] is 'e')
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404 return tmp;
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405 break;
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406 }
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407 return s;
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408 }
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409
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410 /******************************************************************************
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411
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412 Internal function to convert an exponent specifier to a floating
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413 point value.
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414
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415 ******************************************************************************/
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416
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417 private NumType pow10 (uint exp)
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418 {
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419 static NumType[] Powers =
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420 [
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421 1.0e1L,
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422 1.0e2L,
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423 1.0e4L,
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424 1.0e8L,
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425 1.0e16L,
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426 1.0e32L,
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427 1.0e64L,
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428 1.0e128L,
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429 1.0e256L,
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430 ];
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431
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432 if (exp >= 512)
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433 throw new IllegalArgumentException ("Float.pow10 :: exponent too large");
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434
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435 NumType mult = 1.0;
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436 foreach (NumType power; Powers)
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437 {
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438 if (exp & 1)
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439 mult *= power;
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440 if ((exp >>= 1) is 0)
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441 break;
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442 }
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443 return mult;
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444 }
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445
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446
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447 /******************************************************************************
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448
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449 ******************************************************************************/
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450
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451 debug (UnitTest)
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452 {
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453 unittest
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454 {
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455 char[64] tmp;
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456
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457 auto f = parse ("nan");
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458 assert (format(tmp, f) == "nan");
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459 f = parse ("inf");
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460 assert (format(tmp, f) == "inf");
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461 f = parse ("-nan");
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462 assert (format(tmp, f) == "-nan");
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463 f = parse (" -inf");
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464 assert (format(tmp, f) == "-inf");
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465
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466 assert (format (tmp, 3.14159, 6) == "3.141590");
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467 assert (format (tmp, 3.14159, 4) == "3.1416");
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468 assert (parse ("3.5") == 3.5);
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469 assert (format(tmp, parse ("3.14159"), 6) == "3.141590");
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470 }
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471 }
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472
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473
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474 debug (Float)
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475 {
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476 import tango.io.Console;
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477
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478 void main()
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479 {
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480 char[20] tmp;
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481
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482 Cout (format(tmp, 1)).newline;
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483 Cout (format(tmp, 0)).newline;
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484 Cout (format(tmp, 0.000001)).newline;
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485
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486 Cout (format(tmp, 3.14159, 6, 0)).newline;
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487 Cout (format(tmp, 3e100, 6, 3)).newline;
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488 Cout (format(tmp, 314159, 6)).newline;
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489 Cout (format(tmp, 314159123213, 6, 15)).newline;
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490 Cout (format(tmp, 3.14159, 6, 2)).newline;
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491 Cout (format(tmp, 3.14159, 6, 2)).newline;
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492 Cout (format(tmp, 0.00003333, 6, 2)).newline;
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493 Cout (format(tmp, 0.00333333, 6, 3)).newline;
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494 Cout (format(tmp, 0.03333333, 6, 2)).newline;
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495 Cout.newline;
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496
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497 Cout (format(tmp, -3.14159, 6, 0)).newline;
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498 Cout (format(tmp, -3e100, 6, 3)).newline;
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499 Cout (format(tmp, -314159, 6)).newline;
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500 Cout (format(tmp, -314159123213, 6, 15)).newline;
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501 Cout (format(tmp, -3.14159, 6, 2)).newline;
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502 Cout (format(tmp, -3.14159, 6, 2)).newline;
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503 Cout (format(tmp, -0.00003333, 6, 2)).newline;
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504 Cout (format(tmp, -0.00333333, 6, 3)).newline;
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505 Cout (format(tmp, -0.03333333, 6, 2)).newline;
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506 Cout.newline;
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507
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508 Cout (truncate(format(tmp, 30, 6))).newline;
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509 Cout (truncate(format(tmp, 3.14159, 6, 0))).newline;
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510 Cout (truncate(format(tmp, 3e100, 6, 3))).newline;
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511 Cout (truncate(format(tmp, 314159, 6))).newline;
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512 Cout (truncate(format(tmp, 314159123213, 6, 15))).newline;
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513 Cout (truncate(format(tmp, 3.14159, 6, 2))).newline;
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514 Cout (truncate(format(tmp, 3.14159, 6, 2))).newline;
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515 Cout (truncate(format(tmp, 0.00003333, 6, 2))).newline;
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516 Cout (truncate(format(tmp, 0.00333333, 6, 3))).newline;
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517 Cout (truncate(format(tmp, 0.03333333, 6, 2))).newline;
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518
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519 }
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520 }
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