Table of Contents
In this section we describe the layout of an Alex lexical specification.
We begin with the lexical syntax; elements of the lexical syntax are referred to throughout the rest of this documentation, so you may need to refer back to the following section several times.
Alex's lexical syntax is given below. It is written as a set of macro definitions using Alex's own syntax. These macros are used in the BNF specification of the syntax later on.
$digit = [0-9]
$octdig = [0-7]
$hexdig = [0-9A-Fa-f]
$special = [\.\;\,\$\|\*\+\?\#\~\-\{\}\(\)\[\]\^\/]
$graphic = $printable # $white
@string = \" ($graphic # \")* \"
@id = [A-Za-z][A-Za-z'_]*
@smac = '$' id
@rmac = '@' id
@char = ($graphic # $special) | @escape
@escape = '\\' ($printable | 'x' $hexdig+ | 'o' $octdig+ | $digit+)
@code = -- curly braces surrounding a Haskell code fragment