Selasa, 24 November 2009

Perl program that generates... Perl programs

Data::Schema is a module that I wrote to do data structure validation (using another data structure acting as a schema). I had not been terribly happy with the validation speed, ranging in about 100 validations/sec for schemas that are only barely complex. This is not bad, actually, because Data::FormValidator also performs more or less the same. But that was below expectation.

Last week I suddenly realized, writing data validator or a templating system is essentially writing a [mini] language, with our schema/template as the miniprogram and our [Perl] program as the interpreter. To make our miniprogram faster, we can compile it into Perl.

FastTemplate from PHP quickly comes to mind. I remember that it was advertised as being fast because it converts the template into PHP code (e.g. into a bunch of echo's, if/else's, and for loops). And I think there must be at least half a dozen Perl-based template languages on CPAN doing the same. Although I'm not sure about how common data validators compile schemas into Perl code.

So anyway, starting from 0.12, Data::Schema can convert schema into Perl subroutines and use it to validate data structures. Validation speed jumps about one order of magnitude faster, and I'm a happy guy again.

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