Lexical Specifications

Keywords

array, if, then, else, while, for, to, do, let, in, end, of, break, nil, function, var, type, import and primitive

Object-related keywords

The keywords class, extends, method and new are reserved for object-related constructions. They are valid keywords when the object extension of the language is enabled, and reserved words if this extension is disabled (i.e. they cannot be used as identifiers in object-less syntax).

Symbols

,, :, ;, (, ), [, ], {, }, ., +, -, *, /, =, <>, <, <=, >, >=, &, |, and :=

White characters

Space and tabulations are the only white space characters supported. Both count as a single character when tracking locations.

End-of-line

End of lines are \n\r, \r\n, \r and \n, freely intermixed.

Strings

The strings are ANSI-C strings: enclosed by ", with support for the following escapes:

\a, \b, \f, \n, \r, \t, \v

Control characters.

\num

The character which code is num in octal. Valid character codes belong to an extended (8-bit) ASCII set, i.e. values between 0 and 255 in decimal (0 and 377 in octal). num is composed of exactly three octal characters, and any invalid value is a lexical error.

\xnum

The character which code is num in hexadecimal (upper case or lower case or mixed). num is composed of exactly two hexadecimal characters. Likewise, expected values belong to an extended (i.e. 8-bit) ASCII set.

\\

A single backslash.

\"

A double quote.

\character

If no rule above applies, this is an error.

All the other characters are plain characters and are to be included in the string. In particular, multi-line strings are allowed.

Comments

Like C comments, but can be nested:

/* Comment
   /* Nested comment */
   Comment */

Identifiers

Identifiers start with a letter, followed by any number of alphanumeric characters plus the underscore. Identifiers are case sensitive. Moreover, the special _main string is also accepted as a valid identifier.

id = letter { letter | digit | "_" } | "_main" ;

Numbers

There are only integers in Tiger, i.e. values between 0 and \(2^{31} - 1\) = 2147483647. More explanations can be found in TC-1/2-Lexer FAQ.

integer = digit { digit } ;

Invalid characters

Any other character is invalid.