[apple/libc.git] / stdlib / OpenBSD / ecvt.3

.\" $OpenBSD: ecvt.3,v 1.7 2004/01/25 14:48:32 jmc Exp $
.\"
.\" Copyright (c) 2002 Todd C. Miller <Todd.Miller@courtesan.com>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.\" Sponsored in part by the Defense Advanced Research Projects
.\" Agency (DARPA) and Air Force Research Laboratory, Air Force
.\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
.\"
.Dd December 1, 2002
.Dt ECVT 3
.Os
.Sh NAME
.Nm ecvt ,
.Nm fcvt ,
.Nm gcvt
.Nd convert double to
.Tn ASCII
string
.Sh SYNOPSIS
.Fd #include <stdlib.h>
.Ft char *
.Fn ecvt "double value" "int ndigit" "int *decpt" "int *sign"
.Ft char *
.Fn fcvt "double value" "int ndigit" "int *decpt" "int *sign"
.Ft char *
.Fn gcvt "double value" "int ndigit" "char *buf"
.Sh DESCRIPTION
.Bf -symbolic
These functions are provided for compatibility with legacy code.
New code should use the
.Xr snprintf 3
function for improved safety and portability.
.Ef
.Pp
The
.Fn ecvt ,
.Fn fcvt
and
.Fn gcvt
functions convert the double precision floating-point number
.Fa value
to a NUL-terminated
.Tn ASCII
string.
.Pp
The
.Fn ecvt
function converts
.Fa value
to a NUL-terminated string of exactly
.Fa ndigit
digits and returns a pointer to that string.
The result is padded with zeroes from left to right as needed.
There are no leading zeroes unless
.Fa value
itself is 0.
The least significant digit is rounded in an implementation-dependent manner.
The position of the decimal point relative to the beginning of the string
is stored in
.Fa decpt .
A negative value indicates that the decimal point is located
to the left of the returned digits (this occurs when there is no
whole number component to
.Fa value ) .
If
.Fa value
is zero, it is unspecified whether the integer pointed to by
.Fa decpt
will be 0 or 1.
The decimal point itself is not included in the returned string.
If the sign of the result is negative, the integer pointed to by
.Fa sign
is non-zero; otherwise, it is 0.
.Pp
If the converted value is out of range or is not representable,
the contents of the returned string are unspecified.
.Pp
The
.Fn fcvt
function is identical to
.Fn ecvt
with the exception that
.Fa ndigit
specifies the number of digits after the decimal point (zero-padded as
needed).
.Pp
The
.Fn gcvt
function converts
.Fa value
to a NUL-terminated string similar to the %g
.Xr printf 3
format specifier and stores the result in
.Fa buf .
It produces
.Fa ndigit
significant digits similar to the %f
.Xr printf 3
format specifier where possible.
If
.Fa ndigit
does allow sufficient precision, the result is stored in
exponential notation similar to the %e
.Xr printf 3
format specifier.
If
.Fa value
is less than zero,
.Fa buf
will be prefixed with a minus sign.
A decimal point is included in the returned string if
.Fa value
is not a whole number.
Unlike the
.Fn ecvt
and
.Fn fcvt
functions,
.Fa buf
is not zero-padded.
.Sh RETURN VALUES
The
.Fn ecvt ,
.Fn fcvt
and
.Fn gcvt
functions return a NUL-terminated string representation of
.Fa value .
.Sh WARNINGS
The
.Fn ecvt
and
.Fn fcvt
functions return a pointer to internal storage space that will be
overwritten by subsequent calls to either function.
.Pp
The maximum possible precision of the return value is limited by the
precision of a double and may not be the same on all architectures.
.Pp
The
.Xr snprintf 3
function is preferred over these functions for new code.
.Sh SEE ALSO
.Xr printf 3 ,
.Xr strtod 3
.Sh STANDARDS
The
.Fn ecvt ,
.Fn fcvt
and
.Fn gcvt
functions conform to
.St -p1003.1-2001 .
Commit	Line	Data
3d9156a7 A	1	.\" $OpenBSD: ecvt.3,v 1.7 2004/01/25 14:48:32 jmc Exp $
	2	.\"
	3	.\" Copyright (c) 2002 Todd C. Miller <Todd.Miller@courtesan.com>
	4	.\"
	5	.\" Permission to use, copy, modify, and distribute this software for any
	6	.\" purpose with or without fee is hereby granted, provided that the above
	7	.\" copyright notice and this permission notice appear in all copies.
	8	.\"
	9	.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	10	.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	11	.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	12	.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	13	.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
	14	.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
	15	.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
	16	.\"
	17	.\" Sponsored in part by the Defense Advanced Research Projects
	18	.\" Agency (DARPA) and Air Force Research Laboratory, Air Force
	19	.\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
	20	.\"
	21	.Dd December 1, 2002
	22	.Dt ECVT 3
	23	.Os
	24	.Sh NAME
	25	.Nm ecvt ,
	26	.Nm fcvt ,
	27	.Nm gcvt
	28	.Nd convert double to
	29	.Tn ASCII
	30	string
	31	.Sh SYNOPSIS
	32	.Fd #include <stdlib.h>
	33	.Ft char *
	34	.Fn ecvt "double value" "int ndigit" "int decpt" "int sign"
	35	.Ft char *
	36	.Fn fcvt "double value" "int ndigit" "int decpt" "int sign"
	37	.Ft char *
	38	.Fn gcvt "double value" "int ndigit" "char *buf"
	39	.Sh DESCRIPTION
	40	.Bf -symbolic
	41	These functions are provided for compatibility with legacy code.
	42	New code should use the
	43	.Xr snprintf 3
	44	function for improved safety and portability.
	45	.Ef
	46	.Pp
	47	The
	48	.Fn ecvt ,
	49	.Fn fcvt
	50	and
	51	.Fn gcvt
	52	functions convert the double precision floating-point number
	53	.Fa value
	54	to a NUL-terminated
	55	.Tn ASCII
	56	string.
	57	.Pp
	58	The
	59	.Fn ecvt
	60	function converts
	61	.Fa value
	62	to a NUL-terminated string of exactly
	63	.Fa ndigit
	64	digits and returns a pointer to that string.
65	The result is padded with zeroes from left to right as needed.
66	There are no leading zeroes unless
67	.Fa value
68	itself is 0.
69	The least significant digit is rounded in an implementation-dependent manner.
70	The position of the decimal point relative to the beginning of the string
71	is stored in
72	.Fa decpt .
73	A negative value indicates that the decimal point is located
74	to the left of the returned digits (this occurs when there is no
75	whole number component to
76	.Fa value ) .
77	If
78	.Fa value
79	is zero, it is unspecified whether the integer pointed to by
80	.Fa decpt
81	will be 0 or 1.
82	The decimal point itself is not included in the returned string.
83	If the sign of the result is negative, the integer pointed to by
84	.Fa sign
85	is non-zero; otherwise, it is 0.
86	.Pp
87	If the converted value is out of range or is not representable,
88	the contents of the returned string are unspecified.
89	.Pp
90	The
91	.Fn fcvt
92	function is identical to
93	.Fn ecvt
94	with the exception that
95	.Fa ndigit
96	specifies the number of digits after the decimal point (zero-padded as
97	needed).
98	.Pp
99	The
100	.Fn gcvt
101	function converts
102	.Fa value
103	to a NUL-terminated string similar to the %g
104	.Xr printf 3
105	format specifier and stores the result in
106	.Fa buf .
107	It produces
108	.Fa ndigit
109	significant digits similar to the %f
110	.Xr printf 3
111	format specifier where possible.
112	If
113	.Fa ndigit
114	does allow sufficient precision, the result is stored in
115	exponential notation similar to the %e
116	.Xr printf 3
117	format specifier.
118	If
119	.Fa value
120	is less than zero,
121	.Fa buf
122	will be prefixed with a minus sign.
123	A decimal point is included in the returned string if
124	.Fa value
125	is not a whole number.
126	Unlike the
127	.Fn ecvt
128	and
129	.Fn fcvt
130	functions,
131	.Fa buf
132	is not zero-padded.
133	.Sh RETURN VALUES
134	The
135	.Fn ecvt ,
136	.Fn fcvt
137	and
138	.Fn gcvt
139	functions return a NUL-terminated string representation of
140	.Fa value .
141	.Sh WARNINGS
142	The
143	.Fn ecvt
144	and
145	.Fn fcvt
146	functions return a pointer to internal storage space that will be
147	overwritten by subsequent calls to either function.
148	.Pp
149	The maximum possible precision of the return value is limited by the
150	precision of a double and may not be the same on all architectures.
151	.Pp
152	The
153	.Xr snprintf 3
154	function is preferred over these functions for new code.
155	.Sh SEE ALSO
156	.Xr printf 3 ,
157	.Xr strtod 3
158	.Sh STANDARDS
159	The
160	.Fn ecvt ,
161	.Fn fcvt
162	and
163	.Fn gcvt
164	functions conform to
165	.St -p1003.1-2001 .