2.1.3.5 Floating Point Rounding Mode

 

IEEE floating point specifies four possible rounding modes:

:nearest

In this mode, the inexact results are rounded to the nearer of the two possible result values. If the neither possibility is nearer, then the even alternative is chosen. This form of rounding is also called ``round to even'', and is the form of rounding specified for the Common Lisp  round function.

:positive-infinity

This mode rounds inexact results to the possible value closer to positive infinity. This is analogous to the Common Lisp  ceiling function.

:negative-infinity

This mode rounds inexact results to the possible value closer to negative infinity. This is analogous to the Common Lisp  floor function.

:zero

This mode rounds inexact results to the possible value closer to zero. This is analogous to the Common Lisp  truncate function.

 
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