README.md

dp

Dynamic Parser with extensible PEG grammar. Reads as deep

Transparency Rules

• Single unnamed pattern is passed as is: X: x ~ X: <value: x> => value
• Sequence without named arguments results in {}: X: x y ~ X: x y => {}
• Sequence with named arguments is wrapped with rule's name X: <value: x> y ~ X: <value: x> y => X { value }

Rules overriding

You may override rules:

X: a
X: b

Y: X // Same as Y: b

Statement rule

Parsing in Repl starts from Statement rule. If you want to extend parser's syntax, you must override it

>>> EmptyTuple: '(' ')' => "EmptyTuple"
>>> Statement: Rule | EmptyTuple
// >>> Statement: Statement.clone() | EmptyTuple // TODO: copy rule
>>> ()
"EmptyTuple"

Root rule

Parsing in files starts from Root rule. If you want to extend parser's syntax, you must override it

Overriding whitespace

Override Whitespace rule to change skipped characters

Whitespace: /[ ]*/ // Skip only spaces without tabs and newlines

There is context.skip_whitespace special variable that must be set to true for automatic whitespace skipping

Parsing whitespace characters

Parser first tries to parse without ignoring whitespaces. This allows you to parse whitespaces, where needed.

BinaryOrPrefix
	: '+' /[ ]+/ 'x' => "binary"
	| '+' 'x' => "prefix"

Errors

Create error rules for better errors description. By convention, they should start with Invalid. @ means at current location, @lparen means at location of lparen. Note that invalid syntax is still parsed and is accepted as valid alternative.

Tuple: '(' ')' | InvalidTuple
InvalidTuple: <lparen: '('> =>
	throw ExpectedMatching {
		expected: ')',
		at: @,
		to_match: '(',
		unmatched_at: @lparen,
	}

Debugging

To debug library itself call with env RUST_LOG=debug or RUST_LOG=trace

Todo

• Remove on_parse function from rule
• Move logic to syntax
• Export/Import rules
• Rule copy
• Use special rules for whitespace skip
• Add syntax highlighting * [x] Text as keywords * [x] Regex * [x] Strings * [x] Numbers * [x] Special symbols as operators or punctuators * [x] Variables as identifiers (parameter) * [x] RuleName as types * [ ] Make syntax highlighting smarter * [ ] More token subkinds like keyword.text, operator.lparent, etc. * [ ] Syntax highlight shouldn't be affected by errors
• Add documentation
• Simplify separated patterns
• Add #[derive(Rule)] * [ ] Add #[rule] attribute * [ ] Add Self::rule() method * [ ] Add Self::parse(str: &str) method * [ ] Implement deserialize * [ ] On enums every variant is alternative
• Simplify rules
• Remove ';' at end of rules
• Use xxx#tag to add tags like token kinds to values
• Fix left recursion
• Make adding rules to context automatic
• Support code blocks in actions