Grammar Syntax

This extension adds syntax highlighting for .grm files.

Features

• Comments
• Variable tokens
• Constant tokens
• Simple RegEx highlighting

Preview

Syntax

Basic syntax

You can define a rule using this syntax:

rule-name : <rule content>

You should only use lowercase letters and - (hyphen) in naming a rule.

To define a constant token, use this syntax:

CONSTANT-TOKEN : "<token>"

or

CONSTANT-TOKEN : <regex-here>

Use capital letters and - (hyphen) for naming a constant token. You need to surround the token with quotes except when using RegEx. You also must escape the special RegEx characters. You can also use RegEx in defining a constant token. Learn more about RegEx below.

Lastly, you can provide alternate rules using the pipe (|) symbol.

Here is a rule that matches a integer OR a floating-point number:

DIGIT : \d
DOT : "\."

int-or-float : DIGIT+
             | DIGIT+ DOT DIGIT+ # alternatively, match one or more digits, a dot, and one or more digits

^{Yes, I know it can still be simplified.}

Regular expressions

You can use RegEx syntax such as *, +, character classes, capture groups, and more.

For example, to define a constant token that matches any length of letters (including underscore) or numbers:

LETTERS-OR-NUMBERS : [\w\s]+

You can also use RegEx for recursion. For example, here is a rule that matches a term at least once:

DIGIT : \d
DOT : "\."
ADD : "\+" # escaped because + denotes 1 or more in RegEx
SUB : "-"

number : DIGIT+ # match one or more digits 0-9
       | DIGIT+ DOT DIGIT+

term-expr : term-expr ((ADD | SUB) term-expr)*
          | number

Release Notes

1.0.0

Initial release of Grammar Syntax.