# [ot-users] Simplified symbolic functions

```Hi,

I have a symbolic function that I would like to simplify and I do not see how.```
```
Here is the test case. The function has 8 inputs and 2 outputs. In Python it is
simple to define :

def functionCrue(X) :
Q, Ks, Zv, Zm, Hd, Zb, L, B = X
alpha = (Zm - Zv)/L
H = (Q/(Ks*B*sqrt(alpha)))**(3.0/5.0)
Zc = H + Zv
Zd = Zb + Hd
S = Zc - Zd
return [H,S]
myFunction = PythonFunction(8, 2, functionCrue)

As you can see, the code is simplified by intermediate variables which are used
by subsequent Python statements. For exemple, the slope of the river alpha is
first computed, then the height H is computed depending on the slope. Then the
variable S is computed based on Zc and Zd, where Zc is computed depending on
the height H.

When I define the function as a symbolic function, the current definition is
more involved.

inputs = ['Q', 'Ks', 'Zv', 'Zm', 'Hd', 'Zb', 'L', 'B']
formulas = ['(Q/(Ks*B*sqrt((Zm - Zv)/L)))^(3.0/5.0)','(Q/(Ks*B*sqrt((Zm -
Zv)/L)))^(3.0/5.0)+Zv-(Zb + Hd)']
myFunction = SymbolicFunction(inputs, formulas)

As you can see, I cannot reuse the value of the first output into the second
output.

The following interface would be much easier to use. The formulas variable is a
list of couples, where the first item is the name of the output variable and
the second item is the string to evaluate it.

inputs = ['Q', 'Ks', 'Zv', 'Zm', 'Hd', 'Zb', 'L', 'B']
output1 = ['alpha', '(Zm - Zv)/L']
output2 = ['H', '(Q/(Ks*B*sqrt(alpha)))^(3.0/5.0)']
output3 = ['Zc', 'H + Zv']
output4 = ['Zd', 'Zb + Hd']
output5 = ['S', 'Zc - Zd']
formulas = [output1,output2,output3,output4,output5]
myFunction = SymbolicFunction(inputs, formulas)

Is there another way of doing this ? Do you agree that the suggestion is worth
being developed ?

Best regards,

Michaël

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```

crue-8I3O-propagation-simple.py
Description: crue-8I3O-propagation-simple.py

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