[Python-Dev] trunc() (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Sun Jan 27 20:54:02 CET 2008

If I'm following this discussion properly, the advantage of trunc() is that a Real-class-that-isn't-float can define a trunc that can return an Integer-class-that-isn't-int, right?

Depends on what you compare to. Compared to int(), the advantage is that trunc() sends a clear message what its semantics is.

In that case, why not have the Real ABC grow trunc(), ceil(), floor(), and round() methods (replacing the _ varieties), and get rid of the builtins/math-module functions?

x.trunc() is just as clear as trunc(x), and doesn't require a builtin.

+1. Students just asked me why len() is not a method, and I didn't know a good answer; the same holds for many other builtins. This is a clear candidate for a method, IMO.

The syntax when used on float literals is ugly ("2.56 .round()"), but there's no use case for these methods on literals (just write "3").

Actually, it works fine for float literals:

py> 2.45.round() Traceback (most recent call last): File "", line 1, in AttributeError: 'float' object has no attribute 'round'

It's only int literals which have a problem with methods, but then, you won't call any of these on an int literal, normally.

Regards, Martin

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