Find variables and the dependencies between them in code - matlab

Question

I am trying to write a function that finds all the variables in a function which contains computing operations. I do this to find out which variables this block of calculations requires as input arguments to perform the calculations.
A calculation function always gets a table with different parameters as input, accesses certain parameters of that table to calculate certain metrics.
For example my data table T contains the double arrays Power and Time. This table is passed to the function calc_energy which then calculates Energy:
function [ T ] = calc_energy( T )
T.Energy = T.Power .* T.Time;
end
Say whenever a new data table is generated, different calculations as the above one are run automatically. Now if Power itself is calculated by the function calc_power, but calc_energy is run before or parallel to calc_power, then I have a problem because calc_energy doesn't find the required variables in T.
In order to prevent such an error, I want my function check_required_variables to be called inside the calc_energy and check beforehand whether T.Power exists. The thing is that check_required_variables should be a general function that is called in every single calculation function and therefore doesn't know the required variables. It has to find them in the function that it is called by.
function [ T ] = calc_energy( T )
OK = check_required_variables( T, 'calc_energy.m' );
if OK == 1
T.Energy = T.Power .* T.Time;
else
error('Required fields not found');
end
end
Are there any functions that spot the variables Energy, Power and Time used in my code? And are there functions that maybe analyse the dependencies between these variables (Energy dependent on Power and Time)? What are generally clever ways to figure out the ocurring variables just from the code? Any ideas?
I know this is a tough one so I'm thankful for any suggestions.

Answer 1

use isfield
function [ T ] = calc_energy( T )
if all(isfield(T,{'Power','Time'}))
T.Energy = T.Power .* T.Time;
else
error('Nooooope')
end
end
However, knowing which ones are required seems a bit harder.... You can always try to read the .m file, and regexp for T.____, then put the input of that to isfield.
This however, just hints of bad software design. A function should know what it requires to run. What happens if OK is false? It just skips the computation? You can then cascade to hundreds of calls (depend on the application) because the original structure failed to have a variable, or had a typo. I'd take the radically opposite approach to software design:
function [ T ] = calc_energy( T )
assert(all(isfield(T,{'Power','Time'}))); %error if there are not.
T.Energy = T.Power .* T.Time;
end