whalecalf is an actively used grammar language created in 2000. Whale Calf is a research-level parser generator for Boolean grammars, which are context-free grammars augmented with Boolean operations. It is written by Alexander Okhotin in C++, and is mainly aimed at demonstrating different parsing algorithms, of which the most practically useful is the Generalized LR (GLR). The main development took place in 2000-2004, though (as of April 2017) some occasional corrections are still being made.

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Example code from the web:

terminal a, b, c;
S -> C & D;
C -> a C a | a C b | b C a | b C b | c;
D -> a A & a D | b B & b D | c E;
A -> a A a | a A b | b A a | b A b | c E a;
B -> a B a | a B b | b B a | b B b | c E b;
E -> a E | b E | e;

Last updated August 9th, 2020

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