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`mfcalc`

Now that the basics of Bison have been discussed, it is time to move on to a
more advanced problem.^{4} The above calculators provided only
five functions, ‘`+`’, ‘`-`’, ‘`*`’, ‘`/`’ and ‘`^`’. It
would be nice to have a calculator that provides other mathematical
functions such as `sin`

, `cos`

, etc.

It is easy to add new operators to the infix calculator as long as they are
only single-character literals. The lexical analyzer `yylex`

passes
back all nonnumeric characters as tokens, so new grammar rules suffice for
adding a new operator. But we want something more flexible: built-in
functions whose syntax has this form:

function_name(argument)

At the same time, we will add memory to the calculator, by allowing you to create named variables, store values in them, and use them later. Here is a sample session with the multi-function calculator:

$mfcalcpi = 3.141592653589⇒ 3.1415926536

sin(pi)⇒ 0.0000000000

alpha = beta1 = 2.3⇒ 2.3000000000alpha⇒ 2.3000000000ln(alpha)⇒ 0.8329091229exp(ln(beta1))⇒ 2.3000000000 $

Note that multiple assignment and nested function calls are permitted.