4.3 Symbols

The process of reading, i.e., of assembling the input into expressions, has a subprocess, called scanning, that assembles the characters into symbols. A symbol is a sequence of characters that form a lexical unit. The set of symbols consists of keywords, identifiers, strings, integers, and operator and delimiter symbols.

A keyword is a reserved word consisting entirely of lowercase letters (see Keywords). An identifier is a sequence of letters and digits that contains at least one letter and is not a keyword (see Identifiers). An integer is a sequence of digits (see Integers). A string is a sequence of arbitrary characters enclosed in double quotes (see Strings and Characters).

Operator and delimiter symbols are

+    -    *    /    ^    ~   !.
=    <>   <    <=   >    >=  ![
:=   .    ..   ->   ,    ;   !{
[    ]    {    }    (    )    :

Note also that during the process of scanning all whitespace is removed (see Whitespaces).

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