-- | computes an expressions based on an rpn stack
-- molecule names are looked up in a MoleculeMap
-- NOTE: This function expects the RPNstack to be sanitized
-- with respect to the variables, i.e., all variables in
-- the stack are assumed to exist in the VariableMap
rpn_compute :: SymbolTable -> Double -> RpnStack -> Double
rpn_compute _      _   (RpnStack [(Number x)]) = x
rpn_compute :: SymbolTable -> Double -> RpnStack -> Double
rpn_compute _      _   (RpnStack [(Number x)]) = x
rpn_compute _      _   (RpnStack [(Number x)]) = x