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It is more simple to describe the syntax of *rooster* in natural language rather
than in BNF. There are three keywors: "proof", "Kukareku" and "?", any of which
can be sequenced in any order. Everything else is considered comment. 

A major feature of rooster is lack of comment syntax, as compiler just ignores
everything but "proof", "?" and "Kukareku". It makes literate programming very
easy and convenient.

* Compilation
Compilation is done in one pass. Keywoard "proof" pushes the [[*Proof%20combinator][Proof combinator]]
combinator to the top of a stack. Keyword "Kukareku" pushes the [[*Kukareku%20combinator][Kukareku
combinator]] to the stack. Keyword "?" pops two entities from the stack (the
topmost one /a/ and, well, the "other" one /b/), then pushes /(ba)/ the stack.

Attempt to pop something from an empty stack results in compilation error. 

Once EOF is reached, the topmost element of the stack is considered resulting
program.