symbol_start and Parsing.symbol_end are to be called in the action part of a grammar rule only. They return the offset of the string that matches the left-hand side of the rule: symbol_start() returns the offset of the first character; symbol_end() returns the offset after the last character. The first character in a file is at offset 0.

See Parsing.symbol_start.

Same as Parsing.symbol_start and Parsing.symbol_end, but return the offset of the string matching the nth item on the right-hand side of the rule, where n is the integer parameter to rhs_start and rhs_end. n is 1 for the leftmost item.

See Parsing.rhs_start.

Same as symbol_start, but return a position instead of an offset.

Same as symbol_end, but return a position instead of an offset.

Same as rhs_start, but return a position instead of an offset.

Same as rhs_end, but return a position instead of an offset.

Empty the parser stack. Call it just after a parsing function has returned, to remove all pointers from the parser stack to structures that were built by semantic actions during parsing. This is optional, but lowers the memory requirements of the programs.

Raised when a parser encounters a syntax error. Can also be raised from the action part of a grammar rule, to initiate error recovery.

Control debugging support for ocamlyacc-generated parsers. After Parsing.set_trace true, the pushdown automaton that executes the parsers prints a trace of its actions (reading a token, shifting a state, reducing by a rule) on standard output. Parsing.set_trace false turns this debugging trace off. The boolean returned is the previous state of the trace flag.