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Re^8: Array/List Strangeness

by Taulmarill (Deacon)
on Aug 05, 2009 at 13:29 UTC ( [id://786110] : note . print w/replies, xml ) Need Help??

in reply to Re^7: Array/List Strangeness
in thread Array/List Strangeness

I admit that i might have misunderstood something here .... although i'm not sure what....

Could we from now on agree not to talk about (non)existing array elements, but about elements <= $#array and elements > $#array. That might make things easier for my twisted, sleep deprived mind.

update: also i'd like $[ to stay 0.

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Re^9: Array/List Strangeness
by LanX (Saint) on Aug 05, 2009 at 16:28 UTC
    Could we from now on agree not to talk about (non)existing array elements,

    Well we have an exists function, why shouldn't we talk about (non)existing array elements? :-)

    Existence is an an important point to describe the behaviors of slicing, i.e. mostly returning undef for non-existing elements. (And I think what ikegami meant)

    Let's express it in LRTs (Lanx's Rule of Thumb ;-)

    1. Arrayslices (and hashslices) always return values for all requested elements. Not existing elements are represented as 'undef'.

    DB<1> @a=1..2 DB<2> x @a[0,1] 0 1 1 2 DB<3> x @a[0,3] 0 1 1 undef DB<4> x @a[2,3] 0 undef 1 undef DB<5> @a=() DB<6> x @a[1,2] 0 undef 1 undef
    2. Listlices work alike if and only if at least one of the requested elements exists. Otherwise it returns an empty list.

    DB<5> x (1,2)[0,1] 0 1 1 2 DB<6> x (1,2)[0,3] 0 1 1 undef DB<7> x (1,2)[2,3] # DIFFERENT! empty array DB<8> x ()[0..3] # DIFFERENT! empty array DB<9> x (undef,undef)[0,2] 0 undef 1 undef

    Note: Maybe the x command in the debugger should better say "empty list" instead of "empty array"....

    Please correct me if I missed something with this "model" of slice behavior.

    Cheers Rolf