Class BaseParserAbstract

The Semantic Actions wrapper. Should be used to wrap semantic actions that either:

• May fail when executing in "recording phase".
• Have global side effects that should be avoided during "recording phase".

For more information see:

• https://chevrotain.io/docs/guide/internals.html#grammar-recording

Convenience method, same as MANY but the repetition is of one or more. failing to match at least one repetition will result in a parsing error and cause a parsing error.

See

MANY

Convenience method, same as MANY_SEP but the repetition is of one or more. failing to match at least one repetition will result in a parsing error and cause the parser to attempt error recovery.

Note that an additional optional property ERR_MSG can be used to provide custom error messages.

See

MANY_SEP

A Parsing DSL method use to consume a single Token. In EBNF terms this is equivalent to a Terminal.

A Token will be consumed, IFF the next token in the token vector matches tokType. otherwise the parser may attempt to perform error recovery (if enabled).

The index in the method name indicates the unique occurrence of a terminal consumption inside a the top level rule. What this means is that if a terminal appears more than once in a single rule, each appearance must have a different index.

For example:

  this.RULE("qualifiedName", () => {
  this.CONSUME1(Identifier);
    this.MANY(() => {
      this.CONSUME1(Dot);
      // here we use CONSUME2 because the terminal
      // 'Identifier' has already appeared previously in the
      // the rule 'parseQualifiedName'
      this.CONSUME2(Identifier);
    });
  })
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• See more details on the unique suffixes requirement.

Look-Ahead for the Token Vector LA(1) is the next Token ahead. LA(n) is the nth Token ahead. LA(0) is the previously consumed Token.

Looking beyond the end of the Token Vector or before its begining will return in an IToken of type EOF EOF. This behavior can be used to avoid infinite loops.

This is often used to implement custom lookahead logic for GATES. https://chevrotain.io/docs/features/gates.html

Parsing DSL method, that indicates a repetition of zero or more. This is equivalent to EBNF repetition {...}.

Note that there are two syntax forms:

• Passing the grammar action directly:

    this.MANY(() => {
      this.CONSUME(Comma)
      this.CONSUME(Digit)
     })
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• using an "options" object:

    this.MANY({
      GATE: predicateFunc,
      DEF: () => {
             this.CONSUME(Comma)
             this.CONSUME(Digit)
           }
    });
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The optional 'GATE' property in "options" object form can be used to add constraints to invoking the grammar action.

As in CONSUME the index in the method name indicates the occurrence of the repetition production in it's top rule.

Parsing DSL method, that indicates a repetition of zero or more with a separator Token between the repetitions.

Example:

    this.MANY_SEP({
        SEP:Comma,
        DEF: () => {
            this.CONSUME(Number};
            // ...
        })
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Note that because this DSL method always requires more than one argument the options object is always required and it is not possible to use a shorter form like in the MANY DSL method.

Note that for the purposes of deciding on whether or not another iteration exists Only a single Token is examined (The separator). Therefore if the grammar being implemented is so "crazy" to require multiple tokens to identify an item separator please use the more basic DSL methods to implement it.

As in CONSUME the index in the method name indicates the occurrence of the repetition production in it's top rule.

Parsing DSL Method that Indicates an Optional production. in EBNF notation this is equivalent to: "[...]".

Note that there are two syntax forms:

• Passing the grammar action directly:

    this.OPTION(() => {
      this.CONSUME(Digit)}
    );
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• using an "options" object:

    this.OPTION({
      GATE:predicateFunc,
      DEF: () => {
        this.CONSUME(Digit)
    }});
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The optional 'GATE' property in "options" object form can be used to add constraints to invoking the grammar action.

As in CONSUME the index in the method name indicates the occurrence of the optional production in it's top rule.

Parsing DSL method that indicates a choice between a set of alternatives must be made. This is equivalent to an EBNF alternation (A | B | C | D ...), except that the alternatives are ordered like in a PEG grammar. This means that the first matching alternative is always chosen.

There are several forms for the inner alternatives array:

• Passing alternatives array directly:

    this.OR([
      { ALT:() => { this.CONSUME(One) }},
      { ALT:() => { this.CONSUME(Two) }},
      { ALT:() => { this.CONSUME(Three) }}
    ])
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• Passing alternative array directly with predicates (GATE):

    this.OR([
      { GATE: predicateFunc1, ALT:() => { this.CONSUME(One) }},
      { GATE: predicateFuncX, ALT:() => { this.CONSUME(Two) }},
      { GATE: predicateFuncX, ALT:() => { this.CONSUME(Three) }}
    ])
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• These syntax forms can also be mixed:

    this.OR([
      {
        GATE: predicateFunc1,
        ALT:() => { this.CONSUME(One) }
      },
      { ALT:() => { this.CONSUME(Two) }},
      { ALT:() => { this.CONSUME(Three) }}
    ])
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• Additionally an "options" object may be used:

    this.OR({
      DEF:[
        { ALT:() => { this.CONSUME(One) }},
        { ALT:() => { this.CONSUME(Two) }},
        { ALT:() => { this.CONSUME(Three) }}
      ],
      // OPTIONAL property
      ERR_MSG: "A Number"
    })
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The 'predicateFuncX' in the long form can be used to add constraints to choosing the alternative.

As in CONSUME the index in the method name indicates the occurrence of the alternation production in it's top rule.

Will consume a single token and return the next token, meaning the token after the skipped token.

Like AT_LEAST_ONE with the numerical suffix as a parameter, e.g: atLeastOne(0, X) === AT_LEAST_ONE(X) atLeastOne(1, X) === AT_LEAST_ONE1(X) atLeastOne(2, X) === AT_LEAST_ONE2(X) ...

See

AT_LEAST_ONE

By default, all token types may be deleted. This behavior may be overridden in inheriting parsers. The method receives the expected token type. The token that would be deleted can be received with LA.

By default, all tokens type may be inserted. This behavior may be overridden in inheriting Recognizers for example: One may decide that only punctuation tokens may be inserted automatically as they have no additional semantic value. (A mandatory semicolon has no additional semantic meaning, but an Integer may have additional meaning depending on its int value and context (Inserting an integer 0 in cardinality: "[1..]" will cause semantic issues as the max of the cardinality will be greater than the min value (and this is a false error!).

Like CONSUME with the numerical suffix as a parameter, e.g: consume(0, X) === CONSUME(X) consume(1, X) === CONSUME1(X) consume(2, X) === CONSUME2(X) ...

See

CONSUME

Deprecated

• will be removed in the future

Returns an "imaginary" Token to insert when Single Token Insertion is done Override this if you require special behavior in your grammar. For example if an IntegerToken is required provide one with the image '0' so it would be valid syntactically.

Like MANY with the numerical suffix as a parameter, e.g: many(0, X) === MANY(X) many(1, X) === MANY1(X) many(2, X) === MANY2(X) ...

See

MANY

Like OPTION with the numerical suffix as a parameter, e.g: option(0, X) === OPTION(X) option(1, X) === OPTION1(X) option(2, X) === OPTION2(X) ...

See

OPTION

Like OR with the numerical suffix as a parameter, e.g: or(0, X) === OR(X) or(1, X) === OR1(X) or(2, X) === OR2(X) ...

See

OR

This must be called at the end of a Parser constructor. See: http://chevrotain.io/docs/tutorial/step2_parsing.html#under-the-hood