Problems with mutiple returns

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I have a number of functions where Iwant to return mutiple varaibles.  Not being a proper programmer I can do this by converting numbers to formatted strings, concatenated them and return them a string list. This is a bit clunky to say the least. I'm using Igor 9

I am now try to improve with the multiple return syntax.  I find the structure approach diffecult and again a bit awkward where I have a number of functions to write.  I therefore wrote this example code, which to me is using the syntax according to the Manual 

    Function [X_mid, Y_mid, Z_mid] midpoint(X1, Y1, Z1, X2, Y2, Z2)
        variable X1, Y1, Z1, X2, Y2, Z2 
        variable   X_mid = (X1 + X2) / 2
        variable   Y_mid = (Y1 + Y2) / 2
        variable   Z_mid = (Z1 + Z2) / 2
        
        return [X_mid, Y_mid, Z_mid]
    end

but when compiling, X_mid is highlighted and an error "paramater undeclared" is given.   How do I declare them?

Hi,

You need to declare the variable type in the first line. I got this to compile.

Function [variable X_mid, variable Y_mid, variable Z_mid] midpoint(variable X1,variable Y1,variable Z1,variable X2, variable Y2, variable Z2)
         X_mid = (X1 + X2) / 2
         Y_mid = (Y1 + Y2) / 2
         Z_mid = (Z1 + Z2) / 2
       
        return [X_mid, Y_mid, Z_mid]
 end

What is interesting is that this version doesn't compile complaining about the X1 variable.

Function [variable X_mid, variable Y_mid, variable Z_mid] midpoint( X1, Y1, Z1, X2,  Y2,  Z2)
            variable X1,X2,Y1,Y2,Z1,Z2
         X_mid = (X1 + X2) / 2
         Y_mid = (Y1 + Y2) / 2
         Z_mid = (Z1 + Z2) / 2
       
        return [X_mid, Y_mid, Z_mid]
end

It seems if start declaring inline you must declare them all inline.

Andy

October 26, 2024 at 09:09 am - Permalink

Interesting - I'm using Version: 9.0.6.1 (Build 56660) and similar to you this version complains at the your second snippet .

The first line with all the declarations is even more clunky that my string approach :-) .. but thanks that answers my query.  There must be a better way for this to work.

October 26, 2024 at 10:00 am - Permalink

Andy is right, multiple return syntax requires IP7 inline style parameter declarations. The function header then also get's a bit too long as you already noticed.

IIRC you can break the function declaration line in multiple lines with having a trailing \.

October 26, 2024 at 11:05 am - Permalink

Somewhere, the manual says that all definitions must be in line using multiple return functions.

I'd prefer using a WAVE function for this case.

variable x1, y1, z1, x2, y2, z2
// assign variables
x1 = ...
...
// move to waves
make/FREE/D/N=3 w1, w2
w1 = {x1, y1, z1}
w2 = {x2, y2, z2}
// get mid point
wmp = find_midpoint(w1, w2)
// OR
variable xmp, ymp, zmp
xmp = find_midpoint(w1, w2)[0]
 
 
Function/WAVE find_midpoint(wave w1, wave w2)
     make/FREE/N=3/D wmp
     wmp = (w1 + w2)/2
     return wmp
end

 

October 26, 2024 at 11:12 am - Permalink

I would NOT recommend it, but you could also use pass-by-reference in a pinch:

Function midpoint(&X_mid, &Y_mid, &Z_mid, X1, Y1, Z1, X2, Y2, Z2)
    variable X_mid, Y_mid, Z_mid, X1, Y1, Z1, X2, Y2, Z2
    X_mid = (X1 + X2) / 2
    Y_mid = (Y1 + Y2) / 2
    Z_mid = (Z1 + Z2) / 2
end

This invites difficult-to-find bugs, so you need to be careful. I personally use this approach only for pure output functions with no input.

October 26, 2024 at 09:17 pm - Permalink

Mike,

When declaring parameters inline, I like the following use of whitespace as it is clearer to me than typing it out in a linear fashion.

Function [
    variable X_mid, 
    variable Y_mid, 
    variable Z_mid
    ] midpoint(
    variable X1,
    variable Y1,
    variable Z1,
    variable X2, 
    variable Y2, 
    variable Z2
    )
    
         X_mid = (X1 + X2) / 2
         Y_mid = (Y1 + Y2) / 2
         Z_mid = (Z1 + Z2) / 2
       
        return [X_mid, Y_mid, Z_mid]
 end

 

October 28, 2024 at 08:56 am - Permalink