Updated: April 19, 2023 |

*Break a number into integral and fractional parts*

#include <math.h> double modf( doublevalue, double*iptr); float modff( floatvalue, float*iptr); long double modfl( long doublevalue, long double*iptr);

`value`- The value that you want to break into parts.
`iptr`- A pointer to a location where the function can store the integral part of the number.

- libm
- The general-purpose math library.
- libm-sve
- (QNX Neutrino 7.1 or later) A library that optimizes the code for ARMv8.2 chips that have Scalable Vector Extension hardware.

Your system requirements will determine how you should work with these libraries:

- If you want only selected processes to run with the SVE version, you can include both libraries in your OS image and use the -l m or -l m-sve option to qcc to link explicitly against the appropriate one.
- If you want all processes to use the SVE version, include libm-sve.so in your OS image and set up a symbolic link from libm.so to libm-sve.so. Use the -l m option to qcc to link against the library.

Note:
Compile your program with the -fno-builtin option to prevent the compiler from using a
built-in version of the function.

The modf(), modff(), and modfl() functions
break the given `value` into integral and fractional parts,
each of which has the same sign as the argument.
They store the integral part in the object pointed to by `iptr`.

To check for error situations, use feclearexcept() and fetestexcept(). For example:

- Call
`feclearexcept(FE_ALL_EXCEPT)`before calling modf(), modff(), or modfl(). - On return, if
`fetestexcept(FE_ALL_EXCEPT)`is nonzero, then an error has occurred.

The signed fractional part of `value`.

If value is: |
These functions return: | And set *iptr to: |
Errors: |
---|---|---|---|

±Inf | 0.0, with the same sign as value |
Inf, with the same sign as value |
— |

NaN | NaN | NaN | — |

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.

#include <stdio.h> #include <stdlib.h> #include <math.h> int main( void ) { double integral_value, fractional_part; fractional_part = modf( 4.5, &integral_value ); printf( "%f %f\n", fractional_part, integral_value ); fractional_part = modf( -4.5, &integral_value ); printf( "%f %f\n", fractional_part, integral_value ); return EXIT_SUCCESS; }

produces the output:

0.500000 4.000000 -0.500000 -4.000000

Safety: | |
---|---|

Cancellation point | No |

Interrupt handler | Yes |

Signal handler | Yes |

Thread | Yes |