Calculating dt inside a function

I want to calculate dt inside a function whose variable is t. I try doing as follows:

if t> 0
    dt = t - told
end

told = t

inside the function but I receive the error "undefined variable or function 'told'". Is there a command that will store 'told' to be used at the next time step for the function or am I going about it the wrong way.

[Azzi Abdelmalek]

Is it a function? if yes post its arguments

Answer 1

[Doug Hull]

Can you pass told into the function?

If not, persistent might help you.

Look into the properties of functions and subfunctions here:

[Chris]

The persistent declaration did it. Thanks for your help.