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compat.norational- Rational-less arithmetic
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
to appropriate places. However, to ease the transition, you can
just import this module and the division
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
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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