6.6 Input and Output Functions

Functions that perform input from a stdio stream, and functions that output to a stdio stream, of mpq numbers. Passing a NULL pointer for a stream argument to any of these functions will make them read from stdin and write to stdout, respectively.

When using any of these functions, it is a good idea to include stdio.h before gmp.h, since that will allow gmp.h to define prototypes for these functions.

See also Formatted Output and Formatted Input.

Function: size_t mpq_out_str (FILE *stream, int base, const mpq_t op)

Output op on stdio stream stream, as a string of digits in base base. The base argument may vary from 2 to 62 or from -2 to -36. Output is in the form ‘num/den’ or if the denominator is 1 then just ‘num’.

For base in the range 2..36, digits and lower-case letters are used; for -2..-36, digits and upper-case letters are used; for 37..62, digits, upper-case letters, and lower-case letters (in that significance order) are used.

Return the number of bytes written, or if an error occurred, return 0.

Function: size_t mpq_inp_str (mpq_t rop, FILE *stream, int base)

Read a string of digits from stream and convert them to a rational in rop. Any initial white-space characters are read and discarded. Return the number of characters read (including white space), or 0 if a rational could not be read.

The input can be a fraction like ‘17/63’ or just an integer like ‘123’. Reading stops at the first character not in this form, and white space is not permitted within the string. If the input might not be in canonical form, then mpq_canonicalize must be called (see Rational Number Functions).

The base can be between 2 and 62, or can be 0 in which case the leading characters of the string determine the base, ‘0x’ or ‘0X’ for hexadecimal, 0b and 0B for binary, ‘0’ for octal, or decimal otherwise. The leading characters are examined separately for the numerator and denominator of a fraction, so for instance ‘0x10/11’ is 16/11, whereas ‘0x10/0x11’ is 16/17.