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Re: Palindrome array

by LanX (Chancellor)
on Dec 29, 2012 at 06:13 UTC ( #1010793=note: print w/replies, xml ) Need Help??

in reply to Palindrome array

The ugly truth is both don't work!

eq forces scalar context and is meant to compare strings

So in the first code you are checking if the sizes (after stringification) are equal.

DB<107> @a = 1..3 => (1, 2, 3) DB<108> @a eq "3" => 1

in the second you have scalar from reverse on RHS

DB<123> (reverse @a) => (3, 2, 1) DB<124> scalar (reverse @a) => 321 DB<125> "321" eq (reverse @a) => 1

please stop doing weird things!

you can try the (less weird) smart match operator ~~ to compare arrays.

DB<129> @a=(3,1,3) => (3, 1, 3) DB<130> @a ~~ [reverse @a] => 1 DB<131> @a ~~ [3,1,3] => 1 DB<132> @a=1..3 => (1, 2, 3) DB<133> @a ~~ [reverse @a] => ""

a poor man's solution with eq is to explicitly stringify on both sides.

DB<143> @a=(3,1,3) => (3, 1, 3) DB<144> @ar=reverse @a => (3, 1, 3) DB<145> "@a" => "3 1 3" DB<146> "@a" eq "@ar" => 1

But this depends on the nature of your array elements, don't be too surprised about:

DB<151> "@a" => "3 1 3" DB<152> @b=(3,"1 3") => (3, "1 3") DB<153> "@a" eq "@b" => 1

Cheers Rolf

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[atcroft]: james28909: What about October 5, 1582?
[stevieb]: atcroft: "Make both hands into fists..."... is something my Ma taught me in our native lang, but I was to ignorant and young to pay attention. Thanks for that :)
[atcroft]: stevieb: Sad to say that I only recently learned that particular trick, but I have since found it very useful.... :)
[james28909]: ill be back with a solution eventually
[stevieb]: it's a reminder to re-inforce it :P
[atcroft]: james28909: That particular questions was a bit of trick, actually (depending on the country you are in). More interesting is, if you are trying to subtract from an epoch time, for instance, you might have to consider when/if DST occurs for a location,
[atcroft]: because you may have to adjust the number of seconds you change from an epoch from 86400 (not to mention leap seconds)....
[atcroft]: james28909: Although if your program is using a database, you might be able to "pass the buck" to the database and ask it to do the date change for you....

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