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Returns the absolute value of an integer as a long int .
#include <stdlib.h>long int labs (long int j);
j
A value of type long int .
Initializes a 48-bit uniformly distributed pseudorandom number sequences.
#include <stdlib.h>void lcong48 (unsigned short int param[7]);
param
An array that in turn specifies the initial Xi, the multiplier value a, and the addend value c.
This function generates pseudorandom numbers using the linear congruential algorithm and 48-bit integer arithmetic.You can use lcong48 to initialize the random number generator before you call any of the following functions:
drand48
lrand48
mrand48The lcong48 function specifies the initial Xi value, the multiplier value a, and the addend value c. The param array elements specify the following:
param[0-2] Xi param[3-5] Multiplier a value param[6] 16-bit addend c value After lcong48 has been called, a subsequent call to either srand48 or seed48 restores the standard a and c as specified previously.
The lcong48 function does not return a value.
See also drand48 , lrand48 , mrand48 , srand48 , and seed48 in this section.
Returns its first argument multiplied by 2 raised to the power of its second argument; that is, x(2n) .
#include <math.h>double ldexp (double x, int n);
x
A base value of type double that is to be multiplied by 2n .n
The integer exponent value to which 2 is raised.
x(2 n) The first argument multiplied by 2 raised to the power of the second argument. 0 Indicates underflow; errno is set to ERANGE. HUGE_VAL Indicates overflow; errno is set to ERANGE.
Returns the quotient and the remainder after the division of its arguments.
#include <stdlib.h>ldiv_t ldiv (long int numer, long int denom);
numer
A numerator of type long int .denom
A denominator of type long int .
The type ldiv_t is defined in the <stdlib.h> header file as follows:
typedef struct { long quot, rem; } ldiv_t;See also div in this section.
Signals Curses to leave the cursor at the current coordinates after an update to the window.
#include <curses.h>leaveok (WINDOW *win, bool boolf);
win
A pointer to the window.boolf
A Boolean TRUE or FALSE value. If boolf is TRUE, the cursor remains in place after the last update and the coordinate setting on win changes accordingly. If boolf is FALSE, the cursor moves to the currently specified (y,x) coordinates of win.
This function defaults to moving the cursor to the current coordinates of win. The bool type is defined in the <curses.h> header file as follows:
#define bool int
Sets the members of a structure of type struct lconv with values appropriate for formatting numeric quantities according to the rules of the current locale.
#include <locale.h>struct lconv *localeconv (void);
This function returns a pointer to the lconv structure defined in the <locale.h> header file. This structure should not be modified by the program. It is overwritten by calls to localeconv , or by calls to the setlocale function that change the LC_NUMERIC, LC_MONETARY, or LC_ALL categories.The members of the structure are:
Member Description char *decimal_point The radix character char *thousands_sep The character used to separate groups of digits char *grouping The string that defines how digits are grouped in non-monetary values. char *int_curr_symbol The international currency symbol char *currency_symbol The local currency symbol char *mon_decimal_point The radix character used to format monetary values char *mon_thousands_sep The character used to separate groups of digits in monetary values char *mon_grouping The string that defines how digits are grouped in a monetary value char *positive_sign The string used to indicate a non-negative monetary value char *negative_sign The string used to indicate a negative monetary value char int_frac_digits The number of digits displayed after the radix character in a monetary value formatted with the international currency symbol. char frac_digits The number of digits displayed after the radix character in a monetary value char p_cs_precedes For positive monetary values, this is set to 1 if the local or international currency symbol precedes the number, and it is set to 0 if the symbol succeeds the number. char p_sep_by_space For positive monetary values, this is set to 0 if there is no space between the currency symbol and the number. It is set to 1 if there is a space, and it is set to 2 if there is a space between the symbol and the sign string. char n_cs_precedes For negative monetary values, this is set to 1 if the local or international currency symbol precedes the number, and it is set to 0 if the symbol succeeds the number. char n_sep_by_space For negative monetary values, this is set to 0 if there is no space between the currency symbol and the number. It is set to 1 if there is a space, and it is set to 2 if there is a space between the symbol and the sign string. char p_sign_posn An integer used to indicate where the positive_sign string should be placed for a non-negative monetary quantity. char n_sign_posn An integer used to indicate where the negative_sign string should be placed for a negative monetary quantity. Members of the structure of type char * are pointers to strings, any of which (except decimal_point) can point to "", indicating that the associated value is not available in the current locale or is zero length. Members of the structure of type char are positive numbers, any of which can be CHAR_MAX, indicating that the associated value is not available in the current locale. CHAR_MAX is defined in the <limits.h> header file.
Be aware that the value of the CHAR_MAX macro in the <limits.h> header depends on whether the program is compiled with the /UNSIGNED_CHAR qualifier:
- Use the CHAR_MAX macro as an indicator of a non-available value in the current locale only if the program is compiled without /UNSIGNED_CHAR (/NOUNSIGNED_CHAR is the default).
- If the program is compiled with /UNSIGNED_CHAR, use the SCHAR_MAX macro instead of the CHAR_MAX macro.
In /NOUNSIGNED_CHAR mode, the values of CHAR_MAX and SCHAR_MAX are the same; therefore, comparison with SCHAR_MAX gives correct results regardless of the /[NO]UNSIGNED_CHAR mode used.
The members grouping and mon_grouping point to a string that defines the size of each group of digits when formatting a number. Each group size is separated by a semicolon (;). For example, if grouping points to the string 5;3 and the thousands_sep character is a comma (,), the number 123450000 would be formatted as 1,234,50000.
The elements of grouping and mon_grouping are interpreted as follows:
Value Interpretation CHAR_MAX No further grouping is performed. 0 The previous element is to be used repeatedly 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 values of p_sign_posn and n_sign_posn are interpreted as follows:
Value Interpretation 0 Parentheses surround the number and currency symbol. 1 The sign string precedes the number and currency symbol. 2 The sign string succeeds the number and currency symbol. 3 The sign string immediately precedes the number and currency symbol. 4 The sign string immediately succeeds the number and currency symbol.
x Pointer to the lconv structure.
#include <stdlib.h> #include <stdio.h> #include <limits.h> #include <locale.h> #include <string.h> /* The following test program will set up the British English */ /* locale, and then extract the International Currency symbol */ /* and the International Fractional Digits fields for this */ /* locale and print them. */ int main() { /* Declare variables */ char *return_val; struct lconv *lconv_ptr; /* Load a locale */ return_val = (char *) setlocale(LC_ALL, "en_GB.iso8859-1"); /* Did the locale load successfully? */ if (return_val == NULL) { /* It failed to load the locale */ printf("ERROR : The locale is unknown"); exit(EXIT_FAILURE); } /* Get the lconv structure from the locale */ lconv_ptr = (struct lconv *) localeconv(); /* Compare the international currency symbol string with an */ /* empty string. If they are equal, then the international */ /* currency symbol is not defined in the locale. */ if (strcmp(lconv_ptr->int_curr_symbol, "")) { printf("International Currency Symbol = %s\n", lconv_ptr->int_curr_symbol); } else { printf("International Currency Symbol ="); printf("[Not available in this locale]\n"); } /* Compare International Fractional Digits with CHAR_MAX. */ /* If they are equal, then International Fractional Digits */ /* are not defined in this locale. */ if ((unsigned char) (lconv_ptr->int_frac_digits) != CHAR_MAX) { printf("International Fractional Digits = %d\n", lconv_ptr->int_frac_digits); } else { printf("International Fractional Digits ="); printf("[Not available in this locale]\n"); } }Running the example program produces the following result:
International Currency Symbol = GBP International Fractional Digits = 2
Converts a time value to broken-down local time.
#include <time.h>Function Variants Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-test macros defined enables a local-time-based entry point to this function that is equivalent to the behavior before OpenVMS Version 7.0.struct tm *localtime (const time_t *timer);
struct tm *localtime_r (const time_t *timer, struct tm *result); (ISO POSIX-1)
timer
A pointer to a time in seconds since the Epoch. You can generate this time by using the time function or you can supply a time.result
A pointer to a tm structure where the result is stored. The tm structure is defined in the <time.h> header file, and is also shown in Table REF-4.
The localtime and localtime_r functions convert the time (in seconds since the Epoch) pointed to by timer into a broken-down time, expressed as a local time, and store it in a tm structure.The difference between the localtime_r and localtime functions is that the former stores the result into a user-specified tm structure. The latter stores the result into thread-specific static memory allocated by the Compaq C RTL, and which is overwritten by subsequent calls to localtime ; you must make a copy if you want to save it.
On success, localtime returns a pointer to the tm structure; localtime_r returns its second argument. On failure, these functions return the NULL pointer.
The tm structure is defined in the <time.h> header file and described in Table REF-4.
Table REF-4 tm Structure int tm_sec ; Seconds after the minute (0-60) int tm_min ; Minutes after the hour (0-59) int tm_hour ; Hours since midnight (0-23) int tm_mday ; Day of the month (1-31) int tm_mon ; Months since January (1-11) int tm_year ; Years since 1900 int tm_wday ; Days since Sunday (0-6) int tm_yday ; Days since January 1 (0-365) int tm_isdst ; Daylight Savings Time flag
- tm_isdst = 0 for Standard Time
- tm_isdst = 1 for Daylight Time
long tm_gmtoff ;1 Seconds east of Greenwich (Negative values indicate seconds west of Greenwich) char * tm_zone ;1 Time zone string, for example "GMT"
The type time_t is defined in the <time.h> header file as follows:
typedef long int time_t |
Generally speaking, UTC-based time functions can affect in-memory time-zone information, which is process-wide data. However, if the system time zone remains the same during the execution of the application (which is the common case) and the cache of timezone files is enabled (which is the default), then the _r variant of the time functions asctime_r , ctime_r , gmtime_r and localtime_r , is both thread-safe and AST-reentrant. If, however, the system time zone can change during the execution of the application or the cache of timezone files is not enabled, then both variants of the UTC-based time functions belong to the third class of functions, which are neither thread-safe nor AST-reentrant. |
x Pointer to a tm structure. NULL Indicates failure.
Return the logarithm of their arguments.
#include <math.h>double log (double x);
double log10 (double x);
x
A real number of type double .
The log function performs a natural (base e) logarithm.The log10 functions performs a base 10 logarithm.
x The logarithm of the argument (in the appropriate base). --HUGE_VAL Indicates that the argument is 0 or negative; errno is set to ERANGE.
Provides a way to transfer control from a nested series of function invocations back to a predefined point without returning normally; that is, by not using a series of return statements. The longjmp function restores the context of the environment buffer.
#include <setjmp.h>void longjmp (jmp_buf env, int value);
env
The environment buffer, which must be an array of integers long enough to hold the register context of the calling function. The type jmp_buf is defined in the <setjmp.h> header file. The contents of the general-purpose registers, including the program counter (PC), are stored in the buffer.value
Passed from longjmp to setjmp , and then becomes the subsequent return value of the setjmp call. If value is passed as 0, it is converted to 1.
When setjmp is first called, it returns the value 0. If longjmp is then called, naming the same environment as the call to setjmp , control is returned to the setjmp call as if it had returned normally a second time. The return value of setjmp in this second return is the value you supply in the longjmp call. To preserve the true value of setjmp , the function calling setjmp must not be called again until the associated longjmp is called.The setjmp function preserves the hardware general purpose registers, and the longjmp function restores them. After a longjmp , all variables have their values as of the time of the longjmp except for local automatic variables not marked volatile . These variables have indeterminate values.
The setjmp and longjmp functions rely on the OpenVMS condition-handling facility to effect a nonlocal goto with a signal handler. The longjmp function is implemented by generating a Compaq C RTL specified signal and allowing the OpenVMS condition-handling facility to unwind back to the desired destination. The Compaq C RTL must be in control of signal handling for any Compaq C image.
For Compaq C to be in control of signal handling, you must establish all exception handlers through a call to the vaxc$establish function (rather than LIB$ESTABLISH). See Section 4.2.5 and the vaxc$establish function in this section for more information.
Note
There are Alpha specific, non-standard decc$setjmp and decc$fast_longjmp functions. To use these non-standard functions instead of the standard ones, a program must be compiled with __FAST_SETJMP or __UNIX_SETJMP macros defined.
Unlike the standard longjmp function, the decc$fast_longjmp function does not convert its second argument from 0 to 1. After a call to decc$fast_longjmp , a corresponding setjmp function returns with the exact value of the second argument specified in the decc$fast_longjmp call.
You cannot invoke the longjmp function from a OpenVMS condition handler. However, you may invoke longjmp from a signal handler that has been established for any signal supported by the Compaq C RTL, subject to the following nesting restrictions:
- The longjmp function will not work if invoked from nested signal handlers. The result of the longjmp function, when invoked from a signal handler that has been entered as a result of an exception generated in another signal handler, is undefined.
- Do not invoke the setjmp function from a signal handler unless the associated longjmp is to be issued before the handling of that signal is completed.
- Do not invoke the longjmp function from within an exit handler (established with atexit or SYS$DCLEXH). Exit handlers are invoked after image tear-down, so the destination address of the longjmp no longer exists.
- Invoking longjmp from within a signal handler to return to the main thread of execution might leave your program in an inconsistent state. Possible side effects include the inability to perform I/O or to receive any more UNIX signals.
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