man pages section 3: Basic Library Functions

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Updated: July 2014
 
 

econvert(3C)

Name

econvert, fconvert, gconvert, seconvert, sfconvert, sgconvert, qeconvert, qfconvert, qgconvert - output conversion

Synopsis

#include <floatingpoint.h>

char *econvert(double value, int ndigit, int *decpt, int *sign,
     char *buf);
char *fconvert(double value, int ndigit, int *decpt, int *sign,
     char *buf);
char *gconvert(double value, int ndigit, int trailing, char *buf);
char *seconvert(single *value, int ndigit, int *decpt, int *sign,
     char *buf);
char *sfconvert(single *value, int ndigit, int *decpt, int *sign,
     char *buf);
char *sgconvert(single *value, int ndigit, int trailing, char *buf);
char *qeconvert(quadruple *value, int ndigit, int *decpt, int *sign,
     char *buf);
char *qfconvert(quadruple *value, int ndigit, int *decpt, int *sign
     char *buf);
char *qgconvert(quadruple *value, int ndigit, int trailing, char *buf);

Description

The econvert() function converts the value to a null-terminated string of ndigit ASCII digits in buf and returns a pointer to buf. buf should contain at least ndigit+1 characters. The position of the decimal point relative to the beginning of the string is stored indirectly through decpt. Thus buf == "314" and *decpt == 1 corresponds to the numerical value 3.14, while buf == "314" and *decpt == −1 corresponds to the numerical value .0314. If the sign of the result is negative, the word pointed to by sign is nonzero; otherwise it is zero. The least significant digit is rounded.

The fconvert() function works much like econvert(), except that the correct digit has been rounded as if for sprintf(%w.nf) output with n=ndigit digits to the right of the decimal point. ndigit can be negative to indicate rounding to the left of the decimal point. The return value is a pointer to buf. buf should contain at least 310+max(0,ndigit) characters to accomodate any double-precision value.

The gconvert() function converts the value to a null-terminated ASCII string in buf and returns a pointer to buf. It produces ndigit significant digits in fixed-decimal format, like sprintf(%w.nf), if possible, and otherwise in floating-decimal format, like sprintf(%w.ne); in either case buf is ready for printing, with sign and exponent. The result corresponds to that obtained by

(void) sprintf(buf,``%w.ng'',value) ;

If trailing = 0, trailing zeros and a trailing point are suppressed, as in sprintf(%g). If trailing != 0, trailing zeros and a trailing point are retained, as in sprintf(%#g).

The seconvert(), sfconvert(), and sgconvert() functions are single-precision versions of these functions, and are more efficient than the corresponding double-precision versions. A pointer rather than the value itself is passed to avoid C's usual conversion of single-precision arguments to double.

The qeconvert(), qfconvert(), and qgconvert() functions are quadruple-precision versions of these functions. The qfconvert() function can overflow the decimal_record field ds if value is too large. In that case, buf[0] is set to zero.

The ecvt(), fcvt() and gcvt() functions are versions of econvert(), fconvert(), and gconvert(), respectively, that are documented on the ecvt(3C) manual page. They constitute the default implementation of these functions and conform to the X/Open CAE Specification, System Interfaces and Headers, Issue 4, Version 2.

Usage

IEEE Infinities and NaNs are treated similarly by these functions. ``NaN'' is returned for NaN, and ``Inf'' or ``Infinity'' for Infinity. The longer form is produced when ndigit >= 8.

Attributes

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
MT-Level
MT-Safe

See Also

ecvt(3C),sprintf(3C), attributes(5)