Jeff 'japhy' Pinyan wrote:
On Aug 15, Scott R. Godin said:
quantity 1 - 9 0%
quantity 10 - 19 25%
quantity 20 - 199 40%
quantity 200 - 499 50%
quantity 500+ 55%
I'd like to read it in via a __DATA__ handle, and perform the discount
calculation based on the total # of items (out of 6 individual items,
each priced differently but contributing to the total quantity towards
the discount percentage).
what are some perlish ways one would go about performing this
calculation efficiently ?
Well, if the quantities are going to be relatively small numbers, you
could use an array:
my @discount;
while (<DATA>) {
if (my ($lower, $upper, $disc) = / (\d+) - (\d+) +(\d+)%/) {
@discount[$lower..$upper] = ($disc) x ($upper - $lower + 1);
}
elsif (my ($lower, $disc) = / (\d+)\+ +(\d+)%/) {
$discount[$lower] = $disc;
}
else {
warn "unsupported discount line (#$.): $_";
}
}
Oh, Jolly Good! though I'm somewhat concerned with how much memory that would
take up. Ultimately this would be running as a cgi processing a web-form
submission.
Then you would simply poll @discount to find out the rate; this is
assuming $quantity is some positive number:
my $rate = ($discount[$quantity] || $discount[-1]) / 100;
almost. when $discount[1] = 0 that makes it assume the 55% discount instead. see
below.
If there is no entry for $discount[$quantity], that means it's greater
than 500 (in your sample case), thus it gets the same discount as 500
items. Since $discount[500] is the last element in @discount, it's the
same as $discount[-1].
I've modified it slightly, to add strictness and also my pricing/products table.
#!/usr/bin/perl
use warnings;
use strict;
my (@discount, %price);
while ( <DATA> )
{
chomp;
if ( /^quantity/)
{
my($lower, $upper, $disc);
if ( ($lower, $upper, $disc) = /(\d+)\s+-\s+(\d+)\s+(\d+)%$/ )
{
@discount[$lower..$upper] = ($disc) x ($upper - $lower + 1);
}
elsif ( ($lower, $disc) = /(\d+)\+\s+(\d+)%$/ )
{
$discount[$lower] = $disc;
}
else
{
warn "unsupported discount line (#$.): $_";
}
next;
}
if ( /^price/ )
{
if (my($book, $retail) = /(\w+)\s+\$([\d.]+)$/)
{
$price{$book} = $retail;
}
else
{
warn "unsupported price line (#$.): $_";
}
next;
}
warn "nonmatching line in DATA table: '$_'";# fallthrough
}
for (1 .. 20 )
{
my $rate = (defined($discount[$_]) ? $discount[$_] : $discount[-1]) / 100;
print "$_, $rate\n";
}
__DATA__
quantity 1 - 9 0%
quantity 10 - 19 25%
quantity 20 - 199 40%
quantity 200 - 499 50%
quantity 500+ 55%
price rkh $15.95
price rkp $6.95
price rmh $15.95
price rmp $6.95
price rbh $15.95
price rbp $6.95
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