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Package TWiki::Infix::Parser

A simple stack-based parser that parses infix expressions with nonary, unary and binary operators specified using an operator table.

Escapes are supported in strings, using backslash.

On this page:

new($client_class, \%options) -> parser object

Creates a new infix parser. Operators must be added for it to be useful.

The tokeniser matches tokens in the following order: operators, quotes (" and '), numbers, words, brackets. If you have any overlaps (e.g. an operator '<' and a bracket operator '<<') then the first choice will match.

$client_class needs to be the name of a package that supports the following two functions:

These functions should throw Error::Simple in the event of errors. TWiki::Infix::Node is such a class, ripe for subclassing.

The remaining parameters are named, and specify options that affect the behaviour of the parser:

  1. words=>qr// - should be an RE specifying legal words (unquoted terminals that are not operators i.e. names and numbers). By default this is \w+. It's ok if operator names match this RE; operators always have precedence over atoms.
  2. numbers=>qr// - should be an RE specifying legal numbers (unquoted terminals that are not operators or words). By default this is qr/[+-]?(?:\d+\.\d+|\d+\.|\.\d+|\d+)(?:[eE][+-]?\d+)?/, which matches integers and floating-point numbers. Number matching always takes precedence over word matching (i.e. "1xy" will be parsed as a number followed by a word. A typical usage of this option is when you only want to recognise integers, in which case you would set this to numbers => qr/\d+/.

ObjectMethod addOperator (\%oper)

Add an operator to the parser.

\%oper is a hash (or an object), containing the following fields:

Other fields in the hash can be used for other purposes; the parse tree generated by this parser will point to the hashes passed to this function.

Field names in the hash starting with InfixParser_ are reserved for use by the parser.

ObjectMethod parse ($string) -> $parseTree

Parses $string, calling newLeaf and newNode in the client class as necessary to create a parse tree. Returns the result of calling newNode on the root of the parse.

Throws TWiki::Infix::Error in the event of parse errors.



Revision: r2 - 2008-12-06 - 17:02:22 - TWikiContributor

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