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Discussion on: Programs to Compute Trig Functions in Python, JavaScript, & Perl (with Maclaurin Series)

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matthewpersico profile image
Matthew O. Persico •

One thing you should play with is 'memoization' and recursion. For those not familiar with the term, it is the caching of function results using the arguments as a key. In Perl, it's as simple as using the Memoize module. Not sure about the other languages' implementations.

Now, when calculating the factorial in a loop, memoization may not save you much. But in a recursive implementation, memoization is a tremendous win.

Something for you to have in your back pocket.

As for your Perl, it is very good - clear and very concise. One improvement for space and copy time considerations:

my @nums_to_multiply = (1..$x);
for(@nums_to_multiply){
    $n *= $_;
}
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can be replaced with

for(1..$x) {
    $n *= $_;
}
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That will save you the memory and the time to copy that series into the array.

A second suggestion: 

$i = $i_start;
while($i < $i_start + $ITERATIONS) {
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can be replaced with

use strict; # At the top of the code
...
my $i = $i_start;
my $i_end = $i_start + $ITERATIONS
while($i < $i_end) {
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No need in recalculating the same number over and over in the loop.

Excellent article.

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matthewpersico profile image
Matthew O. Persico •

Also, by adding use strict; at the top of your Perl code, you will get some errors about undefined vars. Just add mys in the appropriate places and you'll be fine. Always include use strict; in addition to use warnings;. It will catch unintended overlapping global usage of variables, which is a bear to debug, especially as the code gets longer. Again, excellent article.