Lexical Structure¶

This section describes the lexical structure of SMOL. We define the grammar using a simple EBNF notation as defined by the W3C.

Line Terminators and Whitespace¶

Whitespace ::= #x20 | #x09 | #x0D | #x0A | #x0C
EOL ::= #x0A | #x0C

The following characters count as whitespace:

Whitespace¶
Code	Name
0x20	Space
0x09	Tab
0x0D	Carriage Return
0x0A	Line Feed
0x0C	Form Feed

Whitespace has no semantic meaning, with the exception of the Line Feed and Carriage Return characters which terminate a line comment.

Comments¶

Comments are syntax elements that are ignored during parsing.

Comment ::= BlockComment | LineComment
BlockComment ::= '/*' .* '*/'
LineComment ::= '//' .* EOL

A block comment starts with /* and extends until the first occurrence of */. A line comment starts with // and extends until the end of the line.

Identifiers¶

Identifiers start with a letter or underscore followed by a sequence of letters, numbers and underscores. A language keyword cannot be used as an identifier.

Identifier ::= [a-zA-Z_] [a-zA-Z0-9_]*

Keywords¶

Any word occurring in the grammar (e.g., class) is a keyword. Keywords cannot be used as identifiers.

TODO: list all language keywords here?

Literals¶

A literal is a textual representation of a value. SMOL supports integer, Boolean, string and float literals.

Literal ::= IntLiteral | FloatLiteral | StringLiteral | BoolLiteral
IntLiteral ::= '0' | '-'? [1-9] [0-9]*
FloatLiteral ::= IntLiteral? '.' [0-9]* ([eE]IntLiteral)?
StringLiteral ::= '"' ('\"' | .)* '"'

String literals are delimited with quotation mark (") characters; quotation marks in the middle of a string are escaped with a backslash (\) character. Strings can contain linebreaks.