Scheme Programmer's Manual

NAME

* - multiplication

LIBRARY

(import (rnrs))                     ;R6RS
(import (rnrs base))                ;R6RS
(import (scheme r5rs))              ;R7RS
(import (scheme base))              ;R7RS

SYNOPSIS

(* number ...)

DESCRIPTION

This procedure returns the product of its arguments.

IMPLEMENTATION NOTES

Chez Scheme: An exact zero is returned when any of the arguments to * is an exact zero.

RETURN VALUES

The return value is exact if all arguments are exact. If any argument is inexact then the result is inexact, unless one of the arguments is an exact zero, in which case the return value can optionally be an exact zero.

In non-R6RS implementations

EXAMPLES

; Examples apply to R6RS. An R5RS/R7RS implementation ; might e.g. not provide rational or complex numbers. (* 6 7) => 42 (* 2 1/3) => 2/3 (* 2 1.57) => 3.14 (* 5 1+2i) => 5+10i

; Examples from R6RS (* 4) => 4 (*) => 1 (* 5 +inf.0) => +inf.0 (* -5 +inf.0) => -inf.0 (* +inf.0 +inf.0) => +inf.0 (* +inf.0 -inf.0) => -inf.0 (* 0 +inf.0) => 0 or +nan.0 (* 0 +nan.0) => 0 or +nan.0 (* 1.0 0) => 0 or 0.0

COMPATIBILITY

R6RS is the only report on Scheme to require a full implementation of the numeric tower. In R7RS code, the feature identifiers exact-closed, exact-complex, ieee-float, and ratios should be consulted before performing arithmetic that requires one of these features.

In R7RS, (* 0 +inf.0) may return 0, or +nan.0, or report that inexact numbers are not supported, or report that non-rational real numbers are not supported, or fail silently or noisily in other implementation-specific ways.

ERRORS

This procedure can raise exceptions with the following condition types:

&assertion (R6RS): An argument was outside its domain.
&implementation-restriction (R6RS): May be raised when applied to mixed non-rational real and non-real complex arguments. Otherwise an unspecified number object is returned.
R7RS: The assertions described above are errors. Implementations may signal an error, extend the procedure's domain of definition to include such arguments, or fail catastrophically.

STANDARDS

R4RS, IEEE Scheme, R5RS, R6RS, R7RS

AUTHORS

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