`compile_pgcl` doesnt like boolean type variables

[dominikgeissler]

When trying to parse bit_flip_conditioning.pgcl one gets the following error

CheckFail(location=VarExpr('b1'), message='Expected numeric value, got BoolType().')

[dominikgeissler]

also fails with random_walk_invariant

CheckFail(location=BinopExpr(operator=Binop.POWER, lhs=BinopExpr(operator=Binop.MINUS, lhs=NatLitExpr(1), rhs=BinopExp...), rhs=VarExpr('c'))), rhs=RealLitExpr("1/2")), message='Expected value of type NatType(bounds=None), got RealType().