The VAL and EVAL functions

There are two ways to evaluate an arbitrary expression at selected coordinates.

value = VAL(expression, x, y )                

value = VAL(expression, x, y, z )

The value of expression is computed at the specified coordinates.  The coordinates must be constants.

This form allows FlexPDE to compute implicit couplings between computation nodes referencing and evaluating the value.  The value is computed and stored at each phase of the solution process, allowing efficient reference in many computations.

value = EVAL(expression, x, y )                

value = EVAL(expression, x, y, z )

The Value of expression is computed at the specified coordinates.  The coordinates may be dynamically variable.

This form does NOT allow FlexPDE to compute implicit couplings between computation nodes referencing and evaluating the value.  The value is recomputed at each reference, possibly leading to increased run time.