Bisonc++ and flexc++ are required to generate the parser and the lexical
scanner. 

If you have icmake installed, simply run 'icmbuild' to create the program
Otherwise the ./build command should work.

./tmp/bin/binary starts an interactive program, each line should either
contain

    ident ( ident )

(blanks are optional, ident is any C++ identifier)

or

    ident = int 

(int: any non-negative int-value)

To end the program: ^D or ^C. Any other input also ends the program (with a
syntax error message)

See also the explanation of the implementation of operator= in ../essence.
