Compaq C
Compaq C Language Reference Manual
9.4 Error Codes (<errno.h>)
The
<errno.h>
header file defines several macros used for error reporting.
Macros
EDOM
ERANGE
Error codes that can be stored in
errno
. They expand to integral constant expressions with unique nonzero
values.
Variable or Macro
errno
An external variable or a macro that expands to a modifiable lvalue
with type
int
, depending on the operating system. The
errno
variable is used for holding implementation-defined error codes from
library routines. All error codes are positive integers. The value of
errno
is 0 at program startup, but is never set to 0 by any library function.
Therefore,
errno
should be set to 0 before calling a library function and then inspected
afterward.
9.5 ANSI C Limits (<limits.h> and <float.h>)
The
<limits.h>
and
<float.h>
header files define several macros that expand to various
implementation-specific limits and parameters, most of which describe
integer and floating-point properties of the hardware. See your
platform-specific Compaq C documentation for details.
9.6 Localization (<locale.h>)
The
<locale.h>
header file declares two functions and one type and defines several
macros.
Type
struct lconv
A structure containing members relating to the formatting of numeric
values. The structure contains the following members in any order, with
values shown in the comments:
char *decimal_point; /* "." */
char *thousands_sep; /* "" */
char *grouping; /* "" */
char *int_curr_symbol; /* "" */
char *currency_symbol; /* "" */
char *mon_decimal_point; /* "" */
char *mon_thousands_sep; /* "" */
char *mon_grouping; /* "" */
char *positive_sign; /* "" */
char *negative_sign; /* "" */
char int_frac_digits; /* CHAR_MAX */
char frac_digits; /* CHAR_MAX */
char p_cs_precedes; /* CHAR_MAX */
char p_sep_by_space; /* CHAR_MAX */
char n_cs_precedes; /* CHAR_MAX */
char n_sep_by_space; /* CHAR_MAX */
char p_sign_posn; /* CHAR_MAX */
char n_sign_posn; /* CHAR_MAX */
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These members are described under the
localeconv
function in this section.
Macros
NULL
LC_ALL
LC_COLLATE
LC_CTYPE
LC_MONETARY
LC_NUMERIC
LC_TIME
Expand to integral constant expressions with distinct values, and can
be used as the first argument to the
setlocale
function.
Functions
char *setlocale(int category, const char *locale);
Selects the appropriate portion of the program's locale as specified by
the category and locale arguments. This function can
be used to change or query the program's entire current locale or
portions thereof. The following values can be specified for the
category argument:
LC_ALL---affects the program's entire locale.
LC_COLLATE---affects the behavior of the
strcoll
and
strxfrm
functions.
LC_CTYPE---affects the behavior of the character-handling functions
and multibyte functions.
LC_MONETARY---affects the monetary-formatting information returned
by the
localeconv
function.
LC_NUMERIC---affects the decimal-point character for the formatted
I/O functions and string-conversion functions, as well as the
nonmonetary formatting information returned by the
localeconv
function.
LC_TIME---affects the behavior of the
strftime
function.
The following values can be specified for the locale
argument:
- "C"---specifies the minimal environment for C translation
- ""---specifies the use of the environment variable corresponding to
category. If this environment variable is not set, the
LANG
environment variable is used. If
LANG
is not set, an error is returned.
At program startup, the equivalent of the following is executed:
The
setlocale
function returns one of the following:
- If a pointer to a string is specified for locale and the
selection can be honored,
setlocale
returns a pointer to the string associated with the specified
category for the new locale. If the selection cannot be
honored,
setlocale
returns a null pointer and the program's locale is not changed.
- If a null pointer is specified for locale,
setlocale
returns a pointer to the string associated with the category
for the program's current locale. The program's locale is not changed.
In either case, the returned pointer to the string is such that a
subsequent call with that string value and its associated category will
restore that part of the program's locale. This string must not be
modified by the program, but it can be overwritten by subsequent calls
to
setlocale
.
struct lconv *localeconv(void);
Sets the components of an object with type
struct lconv
with values appropriate for formatting numeric quantities according to
the rules of the current locale. The structure members with type
char *
are pointers to strings, any of which (except
decimal_point
) can point to "", which indicates that the value has zero length or is
not available in the current locale. Structure members of type
char
are nonnegative numbers, any of which can be
CHAR_MAX
to indicate that the value is not available in the current locale.
Structure members include the following:
char *decimal_point
The decimal-point character used to format nonmonetary quantities.
char *thousands_sep
The character used to separate groups of digits before the decimal
point in formatted nonmonetary quantities.
char *grouping
A string whose elements indicate the size of each group of digits in
formatted nonmonetary quantities.
char *int_curr_symbol
The international currency symbol applicable to the current locale. The
first three characters contain the alphabetic international currency
symbol in accordance with those specified in ISO 4217 Codes for the
Representation of Currency and Funds. The fourth character
(immediately preceding the null character) is the character used to
separate the international currency symbol from the monetary quantity.
char *currency_symbol
The local currency symbol applicable to the current locale.
char *mon_decimal_point
The decimal-point character used to format monetary quantities.
char *mon_thousands_sep
The character used to separate groups of digits before the decimal
point in formatted monetary quantities.
char *mon_grouping
A string whose elements indicate the size of each group of digits in
formatted monetary quantities.
char *positive_sign
The string used to indicate a nonnegative formatted monetary quantity.
char *negative_sign
The string used to indicate a negative formatted monetary quantity.
char int_frac_digits
The number of fractional digits to be displayed in internationally
formatted monetary quantities.
char frac_digits
The number of fractional digits to be displayed in formatted monetary
quantities.
char p_cs_precedes
Set to 1 if the
currency_symbol
precedes the value for a nonnegative formatted monetary quantity; set
to 0 if the
currency_symbol
follows the value.
char p_sep_by_space
Set to 1 if the
currency_symbol
is separated by a space from the value for a nonnegative formatted
monetary quantity; set to 0 if there is no space.
char n_cs_precedes
Set to 1 if the
currency_symbol
precedes the value for a negative formatted monetary quantity; set to 0
if the
currency_symbol
follows the value.
char n_sep_by_space
Set to 1 if the
currency_symbol
is separated by a space from the value for a negative formatted
monetary quantity; set to 0 if there is no space.
char p_sign_posn
Set to a value indicating the positioning of the
positive_sign
for a nonnegative formatted monetary quantity.
char n_sign_posn
Set to a value indicating the positioning of the
negative_sign
for a negative formatted monetary quantity.
The elements of
grouping
and
mon_grouping
are interpreted according to the following:
-
CHAR_MAX
---no further grouping is to be performed.
- 0---the previous element is to be repeatedly used for the remainder
of the digits.
- other---the integer value is the number of digits that
comprise the current group. The next element is examined to determine
the size of the next group of digits before the current group.
The value of
p_sign_posn
and
n_sign_posn
is interpreted as follows:
- 0---parentheses surround the quantity and
currency_symbol
- 1---the sign string precedes the quantity and
currency_symbol
- 2---the sign string follows the quantity and
currency_symbol
- 3---the sign string immediately precedes the
currency_symbol
- 4---the sign string immediately follows the
currency_symbol
The
localeconv
function returns a pointer to the filled in structure. The structure
must not be modified by the program, but might be overwritten by
subsequent calls to
localeconv
or to
setlocale
with categories
LC_ALL
,
LC_MONETARY
, or
LC_NUMERIC
.
9.7 Mathematics (<math.h>)
The
<math.h>
header file defines types, macros, and several mathematical functions.
The functions take
double
arguments and return double-precision values.
The behavior of the functions in this header is defined for all
representable values of their input arguments. Each function executes
as if it were a single operation, without generating any externally
visible exceptions.
For all functions, a domain error occurs if an input argument
is outside the domain over which the mathematical function is defined.
The description of each function lists any domain errors. On a domain
error, the function returns an implementation-defined value; the value
of the
EDOM
macro is stored in
errno
.
For all functions, a range error occurs if the result of the
function cannot be represented as a
double
value. If the result overflows (the magnitude of the result is so large
that it cannot be represented in an object of the specified type), the
function returns the value of the macro
HUGE_VAL
, with the same sign (except for the
tan
function) as the correct value of the function; the value of the
ERANGE
macro is stored in
errno
. If the result underflows (the magnitude of the result is so small
that it cannot be represented in an object of the specified type), the
function returns 0; whether the value of the
ERANGE
macro is stored in
errno
is implementation-defined.
Macros
HUGE_VAL
Expands to a positive
double
expression.
INFINITY
Expands to a constant expression of type
float
representing positive or unsigned infinity, if available; otherwise,
expands to a positive constant of type
float
that overflows at translation time.
NAN
Expands to a constant expression of type
float
representing a quiet NaN.
Trigonometric Functions
double acos(double x);
Returns the value, in radians, of the arc cosine of x in the
range [0,Pi sign]. A domain error occurs for arguments not in the
interval [--1,+1].
double asin(double x);
Returns the value, in radians, of the arc sine of x in the
range [--Pi sign/2,+Pi sign/2]. A domain error occurs for arguments not
in the interval [--1,+1].
double atan(double x);
Returns the value, in radians, of the arc tangent of x in the
range [--Pi sign/2,+Pi sign/2].
double atan2(double y, double x);
Returns the value, in radians, of the arc tangent of
y/x, using the signs of both arguments to determine
the quadrant of the return value. The value returned is in the range
[--Pi sign,+Pi sign]. A domain error may occur if both arguments are 0.
double cos(double x);
Returns the value, in radians, of the cosine of x.
double sin(double x);
Returns the value, in radians, of the sine of x.
double tan(double x);
Returns the value, in radians, of the tangent of x.
Hyperbolic Functions
double cosh(double x);
Returns the value of the hyperbolic cosine of x. A range error
occurs if the magnitude of x is too large.
double sinh(double x);
Returns the value of the hyperbolic sine of x. A range error
occurs if the magnitude of x is too large.
double tanh(double x);
Returns the value of the hyperbolic tangent of x.
Exponential and Logarithmic Functions
double exp(double x);
Returns the value of the exponential function of x. A range
error occurs if the magnitude of x is too large.
double frexp(double value, int *eptr);
Breaks the floating-point number value into a normalized
fraction in the interval [1/2, 1) or 0, which it returns, and an
integral power of 2, which it stores in the
int
object pointed to by eptr. If value is 0, both parts
of the result are 0.
double ldexp(double x, int exp);
Multiplies a floating-point number by an integral power of 2, and
returns the value x x 2exp. A range error
may occur.
double log(double x);
Returns the natural logarithm of x. A domain error occurs if
the argument is negative. A range error may occur if the argument is 0.
double log10(double x);
Returns the base-ten logarithm of x. A domain error occurs if
x is negative. A range error may occur if x is 0.
double modf(double value, double *iptr);
Breaks the argument value into integral and fractional parts,
each of which has the same sign as the argument. The
modf
function returns the signed fractional part and stores the integral
part as a
double
in the object pointed to by iptr.
Power Functions
double pow(double x, double y);
Returns the value xy. A domain error
occurs if x is negative and y is not an integral
value. A domain error occurs if the result cannot be represented when
x is 0 and y is less than or equal to 0. A range
error may occur.
double sqrt(double x);
Returns the nonnegative square root of x. A domain error
occurs if x is negative.
Nearest Integer, Absolute Value, and Remainder Functions
double ceil(double x);
Returns the smallest integral value not less than x.
double fabs(double x);
Returns the absolute value of a floating-point number x.
double floor(double x);
Returns the largest integral value not greater than x.
double fmod(double x, double y);
Computes the floating-point remainder of x/y. The
fmod
function returns the value x -- i * y, for
some integer i such that if y is nonzero, the result
has the same sign as x and magnitude less than the magnitude
of y. The function returns 0 if y is 0.
9.8 Nonlocal Jumps (<setjmp.h>)
The
<setjmp.h>
header file contains declarations that provide a way to avoid the
normal function call and return sequence, typically to permit an
intermediate return from a nested function call.
Macro
int setjmp(jmp_buf env)
Sets up the local
jmp_buf
buffer and initializes it for the jump (the jump itself is performed
with
longjmp
.) This macro saves the program's calling environment in the
environment buffer specified by the env argument for later use
by the
longjmp
function. If the return is from a direct invocation,
setjmp
returns 0. If the return is from a call to
longjmp
,
setjmp
returns a nonzero value.
Type
jmp_buf
An array type suitable for holding the information needed to restore a
calling environment.
Function
Restores the context of the environment buffer env that was
saved by invocation of the
setjmp
function in
the same invocation of the program. The
longjmp
function does
not work if called from a nested signal handler; the result is undefined.
The value specified by value is passed from
longjmp
to
setjmp
. After
longjmp
is completed, program execution continues as if the
corresponding invocation of
setjmp
had just returned
value. If value is passed to
setjmp
as 0, it is converted to 1.
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