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EiCCA

Wed Jun 14, 2006 11:43 am


Functions and Updating two values

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There are two questions I have here in this topic

1) In C++, you can declare a function type as void, meaning it does not return a value.  What is the term for this in Turing?

2) I have a situation where I need two variables in a funtion to update their values after the function closes.

For example:


function asdf(x : int, y : int) : 
       x := 5
       y := 6
end asdf

put x
put y


In C++, you can do this using refrence paramaters, using the & beside the  paramater name, however I do not know how this is done in Turing.

Help? :D  Thanks a lot


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wtd

Wed Jun 14, 2006 12:54 pm



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1.  Such things are known as procedures in Turing.

2.  You can do this in Turing by prefixing the parameter name with "var ".  However, for such a simple case, there is a better approach.  Simply link both variables into a single data type, then return that.

type Point :
  record
    x, y : int
  end record

Or in C++ simply use the std::pair class as defined by the STL.


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Tony

Wed Jun 14, 2006 6:47 pm



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function asdf(x : int, y : int) : 
       x := 5
       y := 6
end asdf

put asdf(1,2)

the above clearly doesn't work. X and Y are local variables.

What'd you'd need to do is pass the reference to the variable's address. Now you're getting into pointers and what not. Turing might actually have a similar syntax involving &, but I don't recall at the moment. Consult your F10 manual.

Raguardless, the best practice is to have the function return the updated values.


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[Gandalf]

Wed Jun 14, 2006 7:01 pm



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Tony, like wtd said you can get the pass by reference effect by prefixing the parameter name with "var", for example:
procedure changeValue (var num : int) 
    num += 5
end changeValue

var myValue : int := 7
put myValue
changeValue (myValue)
put myValue %outputs 12
Though yes, you could also return a type containing all your data.


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Tony

Wed Jun 14, 2006 7:03 pm



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ah. thx for pointing that out.