NAME Language::Expr - Simple minilanguage for use in expression VERSION version 0.04 SYNOPSIS use Language::Expr; my $le = new Language::Expr; $le->var('a' => 1, 'b' => 2); $le->func(sqr => sub { $_[0] ** 2 }, rand => sub {rand()}); # evaluate expression say $le->eval('$a + sqr($b)'); # 5 # enumerate variables say $le->enum_vars('$a*$a + sqr($b)'); # ['a', 'b'] DESCRIPTION Language::Expr defines a simple, Perl-like expression minilanguage. It supports mathematical and string operators, arrays, hashes, variables, and functions. See Language::Expr::Manual::Syntax for description of the language syntax. The language is very simple. The parser is just around 120 lines long. This distribution consists of the language parser (Language::Expr::Parser), some interpreters (Language::Expr::Interpreter::*), and some compilers (Language::Expr::Compiler::*). ATTRIBUTES interpreted => BOOL Whether to use the interpreter. By default is 0 (use the compiler, which means Language::Expr expression will be compiled to Perl code first before executed). interpreter => OBJ The Language::Expr::Interpreter::Default instance. compiler => OBJ The Language::Expr::Compiler::Perl instance. varenumer => OBJ The Language::Expr::Interpreter::VarEnumer instance. METHODS new() Construct a new Language::Expr object. var(NAME => VALUE, ...) Define variables. func(NAME => CODEREF, ...) Define functions. Dies if function is defined multiple times. eval(STR) => RESULT Evaluate expression in STR and return the result. Will die if there is a parsing or runtime error. By default it uses the compiler unless you set "interpreted" to 1. enum_vars(STR) => ARRAYREF Enumerate variables mentioned in expression STR. Return empty arrayref if no variables are mentioned. FAQ Why yet another simplistic (restricted, etc) language? Why not just Perl? When first adding expression support to Data::Schema, I want a language that is simple enough so I can easily convert it to Perl, PHP, JavaScript, and others. I do not need a fully-fledged programming language (in fact, Expr is not even Turing-complete, it does not support assignment or loops). Instead, I just need some basic stuffs like mathematical/string/logical operators, arrays, hashes, and functions. This language will mostly be used inside templates and schemas. Why don't you use Language::Farnsworth, or Math::Expression, or Math::Expression::Evaluator, or $FOO? I need several compilers and interpreters (some even with different semantics), so that it's easier to start with a simple parser of my own. And of course there are personal preference of language syntax. I want different syntax for (variables, foo operator, etc)! Create your own language :-) Fork this distribution and start modifying the Language::Expr::Parser module. The parser is too slow! I personally am not having problem with performance. In fact, Regexp::Grammmars should be much faster than Parse::RecDescent. If you need faster parsing speed you can take a look at reimplementing the parser using Parse::Yapp, Parse::Eyapp, etc. If you are having performance runtime problem, try switching from using the interpreter to using one of the available compilers. How to show details of errors in expression? This is a TODO item. BUGS Due to possible bugs in Perl's RE engine or Regexp::Grammars or my grammar, some syntax errors will cause further parsing to fail. Variable interpolation inside double quoted strings also doesn't work yet (segfaults). SEE ALSO Syntax reference: Language::Expr::Manual::Syntax Modules that are using Language::Expr: Data::Schema, Data::Template::Expr. Other related modules: Math::Expression, Math::Expression::Evaluator, Language::Farnsworth AUTHOR Steven Haryanto COPYRIGHT AND LICENSE This software is copyright (c) 2010 by Steven Haryanto. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.