formula solver

hi all,

I have written a simple script (in VB) that solves a formula for its zero points. it works ok, but I want to feed the formula into the component like into the "function evaluate"-component.

is there any chance to do this?

perhaps its easier to make this in python, but I don't get the python code working.

Attachments:

formula-solver.gh, 24 KB

Replies to This Discussion

Permalink Reply by djordje on July 23, 2014 at 5:26am

Hi Laurenz,

You can use the eval function to evaluate the string (that's the equation you have) as if it was regular python expression.

Permalink Reply by David Rutten on July 23, 2014 at 5:53am

So why don't you create a string input and feed in the expression?

David Rutten

david@mcneel.com

Permalink Reply by Laurenz Andritz on July 24, 2014 at 2:42am

Hi Djordje,

thank You very much for introducing me into the magic of eval(). It was exactly what I was looking for! Now it works for my needs.

One drawback: the eval()-function seems to slow down the whole thing significantly (hard-coded the component took 78ms, with eval() it took 3.5s !)

Attachments:

formulasolver3.gh, 27 KB

Permalink Reply by djordje on July 26, 2014 at 2:41pm

Yes, looks like eval function can be slow.

Still, I tried using the equation string directly (assigning it to a variable inside of ghpython component), not importing it from outside. And it lowered the computation time to 100ms.

Permalink Reply by Thomas on July 29, 2014 at 2:47pm

You can speed up eval() by using lambdas

f = eval('lambda x: ' + expressionString)

and call the function like

f(5)

Permalink Reply by Laurenz Andritz on August 11, 2014 at 12:24pm

thank You both, now it works at reasonable speed. I think what causes the delay was the position of the "eval"-command, so every time the function was called, the "eval" translated the input one more time.

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