parser_error.md

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parser::error

prser<C, T>::error is a structure returned by parser's method parser<C, T>::get_error().

Call this if your input wasn't parsed successfully and you want to know more details about the error.

attributes

int_t loc

loc is a location of the error

size_t line

line of the error

size_t col

col is a column of the error

std::vector ctxt

Closest matching context

T unexp

Terminal which was scanned in a place where it was not expected

std::vector<exp_prod_t> expv

List of expected tokens and respective productions. Is a vector of exp_prod_t structs.

	typedef struct _exp_prod {
		std::string exp;
		std::string prod_nt;
		std::string prod_body;
		// back track information to higher derivations
		std::vector<_exp_prod> bktrk;
	} exp_prod_t;

methods

std::string to_str(info_lvl lvl);

This method produces a string containing human readable information about the error.

There are three info_lvl's of details you can obtain:

	enum info_lvl {
		INFO_BASIC,
		INFO_DETAILED,
		INFO_ROOT_CAUSE
	};

Default is INFO_ROOT_CAUSE.

example

See basic arithmetic calculator example.

With INFO_DETAILED we get the following error for entering "1-" as an input

Syntax Error: Unexpected end of file at 1:3 (3): 1-
...expecting space due to (ws => • space ws [2,2])
...expecting '(' due to (factor => • '(' ws expr1 ws ')' [2,2])
...expecting digit due to (integer => • digit integer1 [2,2])
...expecting '-' due to (neg => • '-' ws factor [2,2])
...expecting '+' due to (pos => • '+' ws factor [2,2])

For input "5@2" we get

Syntax Error: Unexpected '@' at 1:2 (2): 5@
...expecting '+' due to (add => expr1 ws • '+' ws expr2 [0,1])
...expecting '-' due to (sub => expr1 ws • '-' ws expr2 [0,1])
...expecting '*' due to (mul => expr2 ws • '*' ws factor [0,1])
...expecting space due to (ws => • space ws [1,1])
...expecting '-' due to (div => expr2 ws • '-' ws factor [0,1])
...expecting digit due to (integer1 => • digit integer1 [1,1])

INFO_BASIC level prints just the first line (without lines containing what was expected)