NAME
Math::Expression::Evaluator::Parser  Parse mathematical expressions
SYNOPSIS
use Math::Expression::Evaluator::Parser;
my $exp = '2 + a * 4';
my $ast = Math::Expression::Evaluator::Parser::parse($exp, {});
# $ast is now something like this:
# $ast = ['+',
# 2,
# ['*',
# ['$', 'a'],
# 4
# ]
# ];
DESCRIPTION
This module parses a mathematical expression in usual notation, and turns it into an Abstract Syntax Tree (AST).
If you want to have a simple interface and want to evaluate these ASTs, use Math::Expression::Evaluator.
The following description of the AST structure matches the current implementation, but really is an implementation detail that's subject to change without further notice. In particular a possible addition of meta information (like file and line numbers) might require a change of structure.
The AST is a tree that consists of nested array refs. The first item is a string (until now always a single character), and denotes the type of the node. The rest of the items in the array is a list of its arguments.
For the mathematical symbols +
, 
, *
, /
, ^
(exponentation) this is straight forward, but /
and 
are always treated as prefix ops, so the string '2  3' is actually turned into ['+', 2, ['', 3]]
.
Other AST nodes are
 '$'

['$', $var_name]
represents a variable.  '{'

['{', $expr1, $expr2, ... ]
represents a block, i.e. a list of expressions.  '='

['=', $var, $expr]
represents an assignment, where$expr
is assigned to$var
.  '&'

['&', $name, @args]
is a function toll to the function called$name
.
METHODS
 parse

parse
takes a string and a hash ref, where the hash ref takes configuration parameters. Currently the only allowed option isforce_semicolon
. If set to a true value, it forces statements to be forced by semicolons (so2 3
will be forbidden,2; 3
is still allowed).parse
throws an exception on parse errors.