Spot the deliberate mistake - list-based maths

use strict;

{
    package Calculator;
    use List::Util qw/reduce/;
    sub add      { reduce { $a + $b } @_ }
    sub multiply { reduce { $a * $b } @_ }
}

{
    package main;
    use Test::More tests => 2;
    
    # Calculate the fifth triangular number
    is(
        Calculator->add(1 .. 5),
        15,
        );
    
    # Calculate five factorial
    is(
        Calculator->multiply(1 .. 5),
        120,
        );
}
[download]

perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

Comment on Spot the deliberate mistake - list-based maths Download Code

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Re: Spot the deliberate mistake - list-based maths by BrowserUk (Patriarch) on Apr 26, 2012 at 17:52 UTC
<Reveal this spoiler or all in this thread>	[reply]
Re: Spot the deliberate mistake - list-based maths by Tanktalus (Canon) on Apr 26, 2012 at 22:09 UTC
`$ perl x.pl 1..2 ok 1 ok 2` [download] Ok, so I made a minor change... :-) `- sub add { reduce { $a + $b } @_ } - sub multiply { reduce { $a * $b } @_ } + use Scalar::Util qw/looks_like_number/; + sub add { reduce { $a + $b } grep looks_like_number($_), +@_ } + sub multiply { reduce { $a * $b } grep looks_like_number($_), +@_ }` [download] And, no, I don't particularly recommend this remedy. :-)	[reply] [d/l] [select]
Re: Spot the deliberate mistake - list-based maths by choroba (Cardinal) on Apr 26, 2012 at 21:54 UTC
Years ago, I was bitten by a similar beast when programming AND and OR for an interpreter in Pascal (the zero was coming from a different source, though).	[reply]