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`compat.norational`

- Rational-less arithmetic__Module:__**compat.norational**-
Until release 0.8.7, Gauche didn’t have exact rational numbers. It was able to read the rational number literals such as

`2/3`

, but they are immediately coerced to inexact real numbers (except when it represents a whole integer). And if you divided an exact integer by another exact integer, the result could be coerced to an inexact real if the result wasn’t a whole integer.As of 0.8.8, this is not the case anymore. Exact division always yields exact result, except when the divisor is zero.

(/ 2 3) ⇒ 2/3 (/ 5) ⇒ 1/5 (/ 4 2) ⇒ 2

This is more precise, but has one drawback: exact rational arithmetic is much slower than the integer and inexact real arithmetic. If you inadvertently produce a rational number in the early stage of calculation, and continue to apply exact arithmetic, performance would be degraded miserably.

The proper way to solve this is to insert

`exact->inexact`

to appropriate places. However, to ease the transition, you can just import this module and the division`/`

behaves in the way it used to.(use compat.norational) (/ 2 3) ⇒ 0.6666666666666666 (/ 5) ⇒ 0.2 (/ 4 2) ⇒ 2

The effect is not global, but only to the modules you explicitly import

`compat.norational`

.This module only redefines

`/`

. So if your code has exact rational literals, they are treated as exact rationals rather than coerced to inexact reals. You should prefix rational literals with`#i`

to force Gauche to coerce them to inexact reals:gosh> 1/3 1/3 gosh> #i1/3 0.3333333333333333

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This document was generated by *Shiro Kawai* on *May 28, 2012* using *texi2html 1.82*.