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Re^7: Reliably parsing an integer

by haukex (Bishop)
on Jun 30, 2020 at 09:11 UTC ( #11118712=note: print w/replies, xml ) Need Help??


in reply to Re^6: Reliably parsing an integer
in thread Reliably parsing an integer

I have seen that 'int' can do weird things, and I am not convinced that there is no floating-point corner case somewhere on some hardware that spits out something that looks like an integer, because some inaccuracy cancels out when generating a string from it.

Of course, if you could show an example of this, that'd be much better than a vauge worry. int is documented to return an integer, and hippo's valid_int includes a check that the input is not floating-point.

If you're worried about a cutoff happening at 9,007,199,254,740,991 instead of 9,007,199,254,740,992, both of which are over nine quadrillion, then I suggest you're worrying about the wrong thing: since you're saying you want this to be portable to different machines and different Perls, this cutoff is arbitrary anyway!

If you want a precise cutoff, you should choose a specific one that you are pretty certain will work on all expected architectures, like say 2**31-1, and if you wanted to code super defensively, you can even compare this cutoff to the integer limits I linked to and report an error otherwise.

Besides, the "eq" is actually converting the integer back to a string, which will cost performance.

hippo beat me to it: Perl's internal conversions are very fast, I suspect it'll be negligible. But let's not guess - Benchmark!

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