Regular Expressions

The following regular expressions are used in the lexical analyser:

letter                      [a-zA-Z]
digit                       [0-9]
integer                     {digit}({digit})*
exponent                    [Ee][+-]?{integer}
i                           {integer}
real                        ({i}\.{i}|{i}{exponent}|{i}\.{i}{exponent})
identifier                  ({letter}({letter}|{digit}|_)*)
comment                     --.*
string                      \"(([^\"\n])|\"\")*\"

In english:

• Integers are strings of digits.
• Reals are strings of digits containing a decimal point; or are strings of digits with an optional decimal point, followed by an exponent.
• Identifiers start with a letter and may contain letters, digits, and underscores.
• Strings are enclosed withing double quotes. Strings may not be longer than one line. When an unterminated string is found, it will be noted, and a terminating double quote will be automatically applied.
• We will allow standard ANSI C quoting conventions (i.e., backslashes) in strings and character constants.
• Comments are introduced by two hyphens and extend to the end of the line. At this time, the lexer silently ignores all comments.