Re^2: Proper creation of a negative number

... with s///, consider the character class '[\$,]' in favour of the alternation '\$|,'. I expect, but don't know for certain, that the former would quicker ...

I certainly haven't Benchmark-ed it, but I think that with trie optimization for alternations (introduced with 5.10?), a humble alternation like a|b|c gets compiled to [abc] anyway. Even if not, any difference in speed would not, I think, be perceptible unless you were doing a gazillion matches.

... the '\r' modifier which allows you to chain s/// and y/// operations.

I knew about the /r modifier, but I hadn't really thought about chaining these operations in this way! Come to think of it, such chaining was probably a signficant motive for adding this feature. Granted, the left-associativity of =~ !~ looks a bit strange in conjunction with the right-assoc. of assignment (the RHS ends up in the middle of the expression), but I can live with that. Again, I've done no Benchmark-ing, but if forced, I think I'd say this trick was more likely to yield speed increases than attention to character class vs. alternation (at least in simple cases).

Give a man a fish: <%-(-(-(-<

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Re^3: Proper creation of a negative number by kcott (Archbishop) on Jul 09, 2015 at 03:59 UTC
You appear to have taken a side-issue and thrust it into the limelight. The main focus of my post was about chaining. The opening sentence talked about performing all operations in a single statement. The code was all about chaining. The three documentation links I provided at the end lead to information about chaining. And then there were side-issues: I pointed out that I had used transliteration, instead of substitution (which the OP's code had), because it was quicker. That was an unequivocal statement. [I didn't go into more depth on this issue as it detracted from the chaining operations I was demonstrating. However, it is documented in "perlperf - Perl Performance and Optimization Techniques" (specifically under "Search and replace or tr").] I then went on to say that, if the OP chose not to use transliteration, then a character class might be quicker than alternation. I said "I expect" and "don't know for certain"; and went on to suggest benchmarking. There was no unequivocal statement here. -- Ken	[reply]

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Re^3: Proper creation of a negative number
by kcott (Archbishop) on Jul 09, 2015 at 03:59 UTC

You appear to have taken a side-issue and thrust it into the limelight.

The main focus of my post was about chaining. The opening sentence talked about performing all operations in a single statement. The code was all about chaining. The three documentation links I provided at the end lead to information about chaining.

And then there were side-issues:

I pointed out that I had used transliteration, instead of substitution (which the OP's code had), because it was quicker. That was an unequivocal statement.

[I didn't go into more depth on this issue as it detracted from the chaining operations I was demonstrating. However, it is documented in "perlperf - Perl Performance and Optimization Techniques" (specifically under "Search and replace or tr").]

I then went on to say that, if the OP chose not to use transliteration, then a character class might be quicker than alternation. I said "I expect" and "don't know for certain"; and went on to suggest benchmarking. There was no unequivocal statement here.

-- Ken

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