dynamic formula evaluation

hi Bill,

how can i use visad to read any formula from a
textfield and evaluate it for a given point.
for example ://
if i have two variables x and y and i want to evaluate
f(x,y)=x+(y*2); for any x and y values i want.
//
i want the formula to be dynamic such that it can be
changed in the textfield not inside my program.



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