Re: How to check if a variable's value is equal to a member of a list of values

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Re^2: How to check if a variable's value is equal to a member of a list of values by Jenda (Abbot) on Mar 25, 2013 at 13:20 UTC
And if the hash happens to grow too big, you can tie it to an optimized cached on disk hash using DB_File, BerkeleyDB or similar module. One thing though, it's not necessary to store the 1 in the values. Keep them empty and use exists() `my %set; @set{@values} = (); ... if (exists $set{$key}) ...` [download] Update: Fixed a syntax error (incorrect type of parens). Thanks go to choroba. Jenda Enoch was right! Enjoy the last years of Rome.	[reply] [d/l]
Re^3: How to check if a variable's value is equal to a member of a list of values by cls33 (Novice) on Mar 25, 2013 at 15:24 UTC
Seems like I'm on the right track, but this is a more elegant implementation. I was not previously familiar with the ability to suck an entire array into a hash using the @hash{@array}=() syntax. One quick syntactical question... using this method, how would I set each hash key to a defined static value? Using something like: @hash{@array}='MyValue'; Only seems to set the value for the first key...	[reply]
Re^4: How to check if a variable's value is equal to a member of a list of values by LanX (Saint) on Mar 25, 2013 at 15:36 UTC
> I was not previously familiar with the ability to suck an entire array into a hash it's called "hash slice"! see perldata#Slices > using this method, how would I set each hash key to a defined static value? assign a list of same length `DB<156> @array=1..5 => (1, 2, 3, 4, 5) DB<157> @hash{@array} = ('my val') x @array => ("my val", "my val", "my val", "my val", "my val") DB<158> \%hash => { 1 => "my val", 2 => "my val", 3 => "my val", 4 => "my val", 5 => + "my val" }` [download] Cheers Rolf ( addicted to the Perl Programming Language) UPDATE for completeness TIMTOWTDI: `$hash{$_}="my val" for @array` has less of a memory footprint. and `my %hash = map { $_ => "my val" } @array;` is DRYer and makes sure the whole hash is reinitiated.	[reply] [d/l] [select]
Re^4: How to check if a variable's value is equal to a member of a list of values by choroba (Cardinal) on Mar 25, 2013 at 15:37 UTC
You have to provide a list of values on the right hand side. For example, you can try: `@hash1{@array} = ('value') x @array; @hash2{@array} = 0 .. $#array;` [download] لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l]
Re^5: How to check if a variable's value is equal to a member of a list of values by cls33 (Novice) on Mar 25, 2013 at 16:30 UTC
Re^6: How to check if a variable's value is equal to a member of a list of values by choroba (Cardinal) on Mar 25, 2013 at 16:35 UTC
Re^2: How to check if a variable's value is equal to a member of a list of values by gnosti (Chaplain) on Mar 25, 2013 at 18:54 UTC
I don't see the OP mentioning whether the values to be checked are integer or floating point. Uncertainties in representing floating point values could make hash test useless.	[reply]
Re^3: How to check if a variable's value is equal to a member of a list of values by McA (Priest) on Mar 25, 2013 at 19:31 UTC
This is an interesting point. Do you know what value is taken for the hash key? The string representation or the floating point binary representation? When the first is true than what you said falls in the whole class of floating point related problems, e.g. equality of floats. McA	[reply]
Re^4: How to check if a variable's value is equal to a member of a list of values by BrowserUk (Patriarch) on Mar 25, 2013 at 20:01 UTC
Do you know what value is taken for the hash key? Hash keys are always strings. With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply]

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