GNU Emacs Lisp Reference Manual

3.7: Rounding Operations

The functions ffloor, fceiling, fround and ftruncate take a floating point argument and return a floating point result whose value is a nearby integer. ffloor returns the nearest integer below; fceiling, the nearest integer above; ftruncate, the nearest integer in the direction towards zero; fround, the nearest integer.

Function: ffloor float

This function rounds float to the next lower integral value, and returns that value as a floating point number.

Function: fceiling float

This function rounds float to the next higher integral value, and returns that value as a floating point number.

Function: ftruncate float

This function rounds float towards zero to an integral value, and returns that value as a floating point number.

Function: fround float

This function rounds float to the nearest integral value, and returns that value as a floating point number.