Enter a logical expression to be checked for being a tautology

Order of precedence is: ' * + > =. Use parentheses to enforce grouping.

The full grammar is ([....] denotes optional, {....} denotes 0-or-more-of, | denotes alternatives):

    E -> I [ '=' I ]            expression
    I -> S [ '>' I ]            implication
    S -> P { '+' P }            sum
    P -> L { '*' L }            product
    L -> U { ' }                literal (' is single quote)
    U -> V | C | '(' E ')'      unit

    V -> a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|   variable
         A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z

    C -> 0|1                                                    constant

Whitespace is allowed between any tokens.