Accessing value of a variable inside a function

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I have a variable, " c " defined outside a function as shown (just an example):
c=5;
function sum = add(a, b)
sum = a+b+c
end
Calling the add function by giving inputs for a, b Matlab throws an error saying : Local function name must be different from the script name. I want the value of the variable "c" to be accessed within the function so that if I give input of (2,3) for (a,b) I should be getting an output of sum = 10. Everything works fine if the variable " c " is inside the function but doesnt work when its outside the function. I tried to globally define the variable "c" like:
global c
c=5;
function sum = add(a, b)
global c
sum = a+b+c
end
But still Mathlab throws an error. Can anybody help me with this?
  1 Comment
Stephen23
Stephen23 on 30 Dec 2020
I suspect that you should be parameterizing the function:
Avoid global variables, they cause more problems than they solve.

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Accepted Answer

Image Analyst
Image Analyst on 30 Dec 2020
The global case should not throw an error. However you should not use sum or add as the name of your variables since they're already built-in functions. Is the function in the same m-file as the script? When I do this, all in the same m-file, it works fine:
global c
c=5;
s = myAddition(10, 20)
function theSum = myAddition(a, b)
global c
theSum = a+b+c
end
So, does that work for you? If not, what did you do differently?
  2 Comments
Image Analyst
Image Analyst on 30 Dec 2020
Do not call it add.m. That could cause a problem with the other built-in add functions. So rename it and upload/attach it here. If it's essentially the same as mine, it should run fine.

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More Answers (1)

Walter Roberson
Walter Roberson on 30 Dec 2020
Edited: Walter Roberson on 30 Dec 2020
When you define a script, and you define a function inside the script, then the name of the function cannot be the same as the name of the script.
Also, when you define a variable in a script, functions defined in the script do not have access to the variable. Shared variables are possible only with nested functions.
I suggest that you read
  9 Comments

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