Re^3: Merging Arrays without duplicates

@seen{@A} = ();
is the same as

$seen{$A[0]}) = undef;
$seen{$A[1]}) = undef;
$seen{$A[2]}) = undef;
$seen{$A[3]}) = undef;
...
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@merged = (@A, grep{!exists $seen{$_}} @B);
is the same as

@C = grep{!exists $seen{$_}} @B;
@merged = (@A, @C);
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@C = grep{!exists $seen{$_}} @B;
@C is assigned the contents of @B not seen in %seen. In other words,
@C is assigned the contents of @B not seen in @A.

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Re^4: Merging Arrays without duplicates by perl_krish (Initiate) on Aug 18, 2004 at 19:16 UTC
Hey and what would $seen{$_} do ??? $_ = each value of A and then compare it with each B ? AM i right? Thanks Krishna	[reply]
Re^5: Merging Arrays without duplicates by ikegami (Patriarch) on Aug 18, 2004 at 20:22 UTC
$_ takes each value of @B, since it's `grep {...} @B` @A = (1, 4, 7, 10, 14); @B = (1, 3, 2, 4); @seen{@A} = (); # does: # $seen{ 1} = undef; # $seen{ 4} = undef; # $seen{ 7} = undef; # $seen{10} = undef; # $seen{14} = undef; @C = grep { !exists($seen{$_}) } @B; # In the grep evaluator, $_ takes the value of each # element of argument list, one at a time. # # !exists($seen{1}) evaluates to false (undef). # !exists($seen{3}) evaluates to true (1). # !exists($seen{2}) evaluates to true (1). # !exists($seen{4}) evaluates to false (undef). # # grep returns the values that resulted in true, # so the result is: # @C = (3, 2); @merged = (@A, @C); # @merged = (1, 4, 7, 10, 14, 3, 2); # @A--------------- ----@C [download]	[reply] [d/l] [select]