[theseoafs]

OO languages do not have to do this. Ruby doesn't, for instance (that is, it turns the language into a "mess of boxing and unboxing", but that's invisible to the programmer and makes working with integers so much more efficient). There's simply no reason to allocate integers on the heap -- it's a bad design desicion.

[ForHackernews]

Python statically allocates small integers (-5 to 256), so you're not actually creating a new object unless you're creating one outside that range.

http://www.laurentluce.com/posts/python-integer-objects-impl...

[theseoafs]

Dynamic allocation isn't the only cost there -- a cost that's just as big when you're doing number crunching in Python is cache efficiency. If every number is on the heap, and every number in Python is ~20 bytes long, you're going to have caching problems, even if your numbers only ever range from -5 to 256.

[icebraining]

How does Ruby know that 'a' is an integer and not any other type? Java and C# can use the variable types to track this, but I don't see how would a dynamic language work without tagging the value.

[gregwebs]

My understanding from 5 years ago is that in MRI the leading bit is reserved to indicate whether something is an integer. This of course reduces the size of numbers that fit into a machine word but it seems like a pretty good tradeoff.

[icebraining]

Yeah, apparently they're called tagged pointers. The More You Know.

EDIT: And here's Guido explaining why he didn't want that in Python: https://mail.python.org/pipermail/python-dev/2004-July/04614...

[lispm]

Most Lisp systems use tags. Several data types will have tags included in the data word, like fixnums, characters. Other data types have an extra word.

[dragonwriter]

Ruby -- or more precisely, MRI, though some other interpretations may do something similar -- uses the a fixed set of object_ids (which is what is stored on the stack to locate an object on the heap) for small integers, so if the object_id is within that range, the interpreter uses it directly to calculate the value, and doesn't need to go to the heap to get a value. (MRI does a similar thing with the values nil, true, and false, as well.)

[ForHackernews]

Python does the same thing for integers in the range (-5, 256)

[mantrax5]

One easy way to know is to run it a few times and observe the behavior.

This is why JIT runtimes need a "warm up time" to get really fast, say V8 for JavaScript.