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Re^3: A Case with 5 Var's

by ultibuzz (Monk)
on Jan 25, 2007 at 16:13 UTC ( #596533=note: print w/replies, xml ) Need Help??

in reply to Re^2: A Case with 5 Var's
in thread A Case with 5 Var's

i'm testing a combined hash and bit solution wich untill now looks great,
thx for the great help and examples
kd ultibuzz

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Re^4: A Case with 5 Var's
by pemungkah (Priest) on Jan 25, 2007 at 20:09 UTC
    If your query consists of embedding the available data into a string in a specific order, you could just interpolate it:
    my $query = ":$name:$vorname:$plz:$tel:$tel49:";
    If the query structure needs to look different for each combination of data, you could use the bit vector you're constructing to access a hash:
    my %query_for = ( 0 => "::", 1 => "name IS \$name", 2 => "vorname IS \$name", ... );
    You'd need 2^5 (32) entries in the hash if every possible combination of the five items was valid; if not, you could leave out any invalid combinations. This means that if $query_for{$bit_vector} was undef, you'd know you had an invalid combination without any comparison logic at all.

    Note that I escaped the "query" strings; that way, you can do an eval on the string and interpolate the variables into the query at the time you have the values you want. If the variables weren't escaped, whatever values they had (probably undef) at the time the hash was constructed would be substituted in immediately, and you'd always get queries without any data in them.

    A much more advanced way to do it is to use anonymous subroutines as the entries in the hash:

    my %query_constuctor_for = ( ... 18 => sub { return ":NIL/$vorname::$tel49:" }, 19 => sub { return ":$name/$vorname::$tel49:" }, ... );
    Lookup works the same way, but you'd say
    my $query_maker = $query_constructor_for{$bitvector}; defined $query_maker or die "Combination invalid"; $query = $query_maker->()
    to get your query; the $query_maker->() expression calls the anonymous subroutine that you looked up with $query_constructor_for{$bitvector}. This lets you construct arbitrarily-complicated code to do what's needed for each combination.

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[stevieb]: Damn... just wasted two hours wondering why num 23 wasn't setting bit 5 in a register. I was working on the decimal, but the register holds BCD numbers. Sigh.

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