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lib/Language/FormulaEngine/Parser.pm  view on Meta::CPAN

=head1 SYNOPSIS

  my $parse_tree= Language::FormulaEngine::Parser->new->parse($string);

=head1 DESCRIPTION

This class scans tokens from an input string and builds a parse tree.  In compiler terminology,
it is both a Scanner and Parser.  It performs a top-down recursive descent parse, because this
is easy and gives good error messages.  It only parses strings, but leaves room for subclasses
to implement streaming.  By default, the parser simply applies a Grammar to the input, without
checking whether the functions or variables exist, but can be subclassed to do more detailed
analysis during the parse.

The generated parse tree is made up of Function nodes (each infix operator is converted to a
named function) and each Function node may contain Symbols, Strings, Numbers, and other
Function nodes.  The parse tree can be passed to the Evaluator for instant execution, or passed
to the Compiler to generate an optimized perl coderef.  The parse tree is lightweight, and does
not include token/context information; this could also be added by a subclass.

=head1 PUBLIC API