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46 .TH WCSTOD 3C "Aug 25, 2019"
47 .SH NAME
48 wcstod, wcstof, wcstold, wstod, watof \- convert wide character string to
49 floating-point number
50 .SH SYNOPSIS
51 .nf
52 #include <wchar.h>
53
54 \fBdouble\fR \fBwcstod\fR(\fBconst wchar_t *restrict\fR \fInptr\fR,
55 \fBwchar_t **restrict\fR \fIendptr\fR);
56 .fi
57
58 .LP
59 .nf
60 \fBfloat\fR \fBwcstof\fR(\fBconst wchar_t *restrict\fR \fInptr\fR,
61 \fBwchar_t **restrict\fR \fIendptr\fR);
62 .fi
63
64 .LP
65 .nf
66 \fBlong double\fR \fBwcstold\fR(\fBconst wchar_t *restrict\fR \fInptr\fR,
67 \fBwchar_t **restrict\fR \fIendptr\fR);
68 .fi
69
70 .LP
71 .nf
72 \fBdouble\fR \fBwstod\fR(\fBconst wchar_t *\fR\fInptr\fR, \fBwchar_t **\fR\fIendptr\fR);
73 .fi
74
75 .LP
76 .nf
77 \fBdouble\fR \fBwatof\fR(\fBwchar_t *\fR\fInptr\fR);
78 .fi
79
80 .SH DESCRIPTION
81 The \fBwcstod()\fR, \fBwcstof()\fR, and \fBwcstold()\fR functions convert the
82 initial portion of the wide-character string pointed to by \fInptr\fR to
83 \fBdouble\fR, \fBfloat\fR, and \fBlong double\fR representation, respectively.
84 They first decompose the input wide-character string into three parts:
85 .RS +4
86 .TP
87 1.
88 An initial, possibly empty, sequence of white-space wide-character codes (as
89 specified by \fBiswspace\fR(3C))
90 .RE
91 .RS +4
92 .TP
93 2.
94 A subject sequence interpreted as a floating-point constant or representing
95 infinity or NaN
96 .RE
97 .RS +4
98 .TP
99 3.
100 A final wide-character string of one or more unrecognized wide-character
101 codes, including the terminating null wide-character code of the input
102 wide-character string.
103 .RE
104 .sp
105 .LP
106 Then they attempt to convert the subject sequence to a floating-point number,
107 and return the result.
108 .sp
109 .LP
110 The expected form of the subject sequence is an optional plus or minus sign,
111 then one of the following:
112 .RS +4
113 .TP
114 .ie t \(bu
115 .el o
116 A non-empty sequence of decimal digits optionally containing a radix character,
117 then an optional exponent part
118 .RE
119 .RS +4
120 .TP
121 .ie t \(bu
122 .el o
123 A 0x or 0X, then a non-empty sequence of hexadecimal digits optionally
124 containing a radix character, then an optional binary exponent part
125 .RE
126 .RS +4
127 .TP
128 .ie t \(bu
129 .el o
130 One of INF or INFINITY, or any other wide string equivalent except for case
131 .RE
132 .RS +4
133 .TP
134 .ie t \(bu
135 .el o
136 One of NAN or NAN(\fIn-wchar-sequence\fR(\fIopt\fR)), or any other wide string
137 ignoring case in the NAN part, where:
138 .sp
139 .in +2
140 .nf
141 n-wchar-sequence:
142 digit
143 nondigit
144 n-wchar-sequence digit
145 n-wchar-sequence nondigit
146 .fi
147 .in -2
148
149 .RE
150 .sp
151 .LP
152 In default mode for \fBwcstod()\fR, only decimal, INF/INFINITY, and
153 NAN/NAN(\fIn-wchar-sequence\fR) forms are recognized. In C99/SUSv3 mode,
154 hexadecimal strings are also recognized.
155 .sp
156 .LP
157 In default mode for \fBwcstod()\fR, the \fIn-wchar-sequence\fR in the
158 NAN(\fIn-wchar-sequence\fR) form can contain any character except ')' (right
159 parenthesis) or '\e0' (null). In C99/SUSv3 mode, the \fIn-wchar-sequence\fR can
160 contain only upper and lower case letters, digits, and '_' (underscore).
161 .sp
162 .LP
163 The \fBwcstof()\fR and \fBwcstold()\fR functions always function in
164 C99/SUSv3-conformant mode.
165 .sp
166 .LP
167 The subject sequence is defined as the longest initial subsequence of the input
168 wide string, starting with the first non-white-space wide character, that is of
169 the expected form. The subject sequence contains no wide characters if the
170 input wide string is not of the expected form.
171 .sp
172 .LP
173 If the subject sequence has the expected form for a floating-point number, the
174 sequence of wide characters starting with the first digit or the radix
175 character (whichever occurs first) is interpreted as a floating constant
176 according to the rules of the C language, except that the radix character is
177 used in place of a period, and that if neither an exponent part nor a radix
178 character appears in a decimal floating-point number, or if a binary exponent
179 part does not appear in a hexadecimal floating-point number, an exponent part
180 of the appropriate type with value zero is assumed to follow the last digit in
181 the string. If the subject sequence begins with a minus sign, the sequence is
182 interpreted as negated. A wide-character sequence INF or INFINITY is
183 interpreted as an infinity. A wide-character sequence NAN or
184 NAN(\fIn-wchar-sequence\fR(\fIopt\fR)) is interpreted as a quiet NaN. A pointer
185 to the final wide string is stored in the object pointed to by \fIendptr\fR,
186 provided that \fIendptr\fR is not a null pointer.
187 .sp
188 .LP
189 If the subject sequence has either the decimal or hexadecimal form, the value
190 resulting from the conversion is rounded correctly according to the prevailing
191 floating point rounding direction mode. The conversion also raises floating
192 point inexact, underflow, or overflow exceptions as appropriate.
193 .sp
194 .LP
195 The radix character is defined in the program's locale (category
196 \fBLC_NUMERIC\fR). In the POSIX locale, or in a locale where the radix
197 character is not defined, the radix character defaults to a period ('.').
198 .sp
199 .LP
200 If the subject sequence is empty or does not have the expected form, no
201 conversion is performed; the value of \fInptr\fR is stored in the object
202 pointed to by \fIendptr\fR, provided that \fIendptr\fR is not a null pointer.
203 .sp
204 .LP
205 The \fBwcstod()\fR function does not change the setting of \fBerrno\fR if
206 successful.
207 .sp
208 .LP
209 The \fBwstod()\fR function is identical to \fBwcstod()\fR.
210 .sp
211 .LP
212 The \fBwatof\fR(\fIstr\fR) function is equivalent to \fBwstod(\fR\fInptr\fR\fB,
213 (wchar_t **)NULL)\fR.
214 .SH RETURN VALUES
215 Upon successful completion, these functions return the converted value. If no
216 conversion could be performed, \fB0\fR is returned.
217 .sp
218 .LP
219 If the correct value is outside the range of representable values,
220 \fB\(+-HUGE_VAL\fR, \fB\(+-HUGE_VALF\fR, or \fB\(+-HUGE_VALL\fR is returned
221 (according to the sign of the value), a floating point overflow exception is
222 raised, and \fBerrno\fR is set to \fBERANGE\fR.
223 .sp
224 .LP
225 If the correct value would cause an underflow, the correctly rounded result
226 (which may be normal, subnormal, or zero) is returned, a floating point
227 underflow exception is raised, and \fBerrno\fR is set to \fBERANGE\fR.
228 .SH ERRORS
229 The \fBwcstod()\fR and \fBwstod()\fR functions will fail if:
230 .sp
231 .ne 2
232 .na
233 \fBERANGE\fR
234 .ad
235 .RS 10n
236 The value to be returned would cause overflow or underflow.
237 .RE
238
239 .sp
240 .LP
241 The \fBwcstod()\fR and \fBwcstod()\fR functions may fail if:
242 .sp
243 .ne 2
244 .na
245 \fBEINVAL\fR
246 .ad
247 .RS 10n
248 No conversion could be performed.
249 .RE
250
251 .SH USAGE
252 Because 0 is returned on error and is also a valid return on success, an
253 application wishing to check for error situations should set \fBerrno\fR to 0
254 call \fBwcstod()\fR, \fBwcstof()\fR, \fBwcstold()\fR, or \fBwstod()\fR, then
255 check \fBerrno\fR and if it is non-zero, assume an error has occurred.
256 .SH ATTRIBUTES
257 See \fBattributes\fR(5) for descriptions of the following attributes:
258 .sp
259
260 .sp
261 .TS
262 box;
263 l | l
264 l | l .
265 ATTRIBUTE TYPE ATTRIBUTE VALUE
266 _
267 Interface Stability T{
268 \fBwcstod()\fR, \fBwcstof()\fR, and \fBwcstold()\fR are Standard.
269 T}
270 _
271 MT-Level MT-Safe
272 .TE
273
274 .SH SEE ALSO
275 \fBiswspace\fR(3C), \fBlocaleconv\fR(3C), \fBscanf\fR(3C), \fBsetlocale\fR(3C),
276 \fBwcstol\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)