algebraic inputs for variables

[georgekenison]

Consider the following (probabilistic) program, say fibonacci.prob, for the Fibonacci recurrence with algebraic initial values.

f0 = 1
f1 = 2**(1/2)
while true:
    f0o = f0
    f1o = f1
    f0 = f1
    f1 = f0o + f1o
end

or

f0 = 1
f1 = sqrt(2)
while true:
    f0o = f0
    f1o = f1
    f0 = f1
    f1 = f0o + f1o
end

I run the following task python3.8 polar.py benchmarks/fibonacci.prob --plot f0 and obtain the outputs

Computing samplesPolynomial sqrt(2) is not a number in state {f0: 0.0}

and

Unexpected token Token('BOPEN', '(') at line 2, column 10.
Expected one of: 
	* RBRACE
	* _NL
	* BCLOSE
	* LBRACE
	* MULT
	* MINUS
	* PLUS
	* COP
	* OR
	* POW
	* COMMA
	* DIV
	* COLON
	* AND

respectively.

It would be useful if Polar could interpret algebraic inputs (in common standard forms).