Re^5: Problem with a sort result: weird subtraction behaviour?

Infact it is something strange: while in motorbike this morning i thought i was wrong (in my previous post): the results of subtraction must be valid too when sorting: big minus less is greater than zero; equal minus equal is 0 and little minus big is less than zero:

perl -e "print join qq(\n),sort {$a - $b} @ARGV" 33 1 2 99
1
2
33
99
# same result using <=> or -
[download]

using big nums give me incorrect ordering using subtraction when one number is ten digits or more:

perl -e "print join qq(\n),sort {$a - $b} @ARGV" 10000000000 3 2
10000000000
2
3
[download]

There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.

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Re^6: Problem with a sort result: weird subtraction behaviour? by kzwix (Sexton) on Jan 27, 2016 at 14:32 UTC
Discipulus, rdfield, you are both correct: This is a problem with long integers. What I don't understand is: Why are the integers correctly remembered, correctly displayed, but incorrectly compared to 0 ? Because, let's face it, it's the core of the problem: When it's a "small" number, it is correctly evaluated as positive, negative, or null. When it is a "big" number, then there may be problems in evaluating the sign. Much like if some bit from the big number was used as a sign bit, or whatever, where the real good practice would merely be to check the sign at the start of the number string... I mean, if it starts with a "+" or a digit, then it's positive. If it starts with a "-", it's negative. We keep that "sign", unless all digits are 0 -> in which case it is merely null. Did I miss something, there ?	[reply]
Re^7: Problem with a sort result: weird subtraction behaviour? by choroba (Cardinal) on Jan 27, 2016 at 18:47 UTC
The problem is that the code that implements the behaviour is in C. There's no number string, there are different integer types with different byte sizes. ($q=q:Sq=~/;[c](.)(.)/;chr(-\|\|-\|5+lengthSq)`"S\|oS2"`map{chr \|+ord }map{substrSq`S_+\|`\|}3E\|-\|`7**2-3:)=~y+S\|`+$1,++print+eval$q,q,a, [download]	[reply] [d/l]