parser_of_logic_expressions

parser_of_logic_expressions — a simple parser for propositional logic expressions.

The project reads lines with expressions (one expression per line), builds a syntactic tree, and can output a simplified, bracketed form of the expression.

Technical description of parsing

Input: one or more text lines with logical expressions. Supported are atoms (names, true/false), parentheses (), [], {}, unary negation !, binary operators &, |, ^, ↑, ->, <-> with defined priorities. The parser is implemented using pest. The grammar rules are described in src/grammar.pest and include the following rules: atom, primary, negation, and, xor, or, implication, expression, file.

After parsing, the code can output a parse tree or perform a simple transformation — construct a left-sided parenthesized form of the expression for reading.

How to use

The command parse <FILE_PATH> outputs a parse tree for each expression in the file.

The command make_parantecies <IN_PATH> <OUT_PATH> reads the input file and writes to the output file the strings with the parenthesized form of each expression.

Grammar

COMMENT = _{ "//" ~ (!NEWLINE ~ ANY)* }
WHITESPACE = _{ " " | NEWLINE }

atom = @{ (^"true" | ^"false") | (('a'..'z' | 'A'..'Z') ~ (('a'..'z' | 'A'..'Z') | '0'..'9' | "_")*) }
primary = { atom | "(" ~ expression ~ ")" | "[" ~ expression ~ "]" | "{" ~ expression ~ "}" }
negation = { "!"* ~ primary }
and = { negation ~ (("&" | "↑") ~ negation)* }
xor = { and ~ ("^" ~ and)* }
or  = { xor ~ ("|" ~ xor)* }
implication = { or ~ ("->" ~ implication)? }

expression = { implication ~ ("<->" ~ implication)* }
file = { SOI ~ (expression)* ~ EOI }