Thank again to Bill and all who took a look at this. This one is a bit odd. I have multiple copies of Mathematica on desktops and laptops - so I will try this on different machines.

I am also noticing that some parameters being passed into functions with default values do not show up in the variables debug window as numeric values. If arguments with numeric default values are seen by Mathematica as objects instead of numeric values, comparison operators will probably not work as expected and arithmetic operations may be returning a type of object instead of numeric value.

This begs the question: what type of variable is a function argument where the default value is used?

If I write:

H[ depth_, opFreq_: 1000, relPermittivity_: 78] := Module[...];

and call this with H[1.8]. Are opFreq and relPermittivity numeric types or objects? Is there a way to use strong typing in Mathematica?

In languages such as C++ and C#, the type of object or variable determine how comparison operators (such as ==, <=, >=) are interpreted.

Hi Bill,

Here is the output:

Print["Does it work?"]

Does it work?

I'm wondering if there are any conditions that could disable the execution of a loop. While the basic code above works, the loop below does nothing:

rPos = 0; 
    MAXRPOS = (2 N[Pi]);
    radiusInc = N[Pi]/10;


    While[rPos<=MAXRPOS,
       Print@ToString@rPos;
       rPos = rPos + radiusInc];

Sorry below is a more complete code snippet:

rDistance = 5.4;
radiusInc = N[Pi]/10;
planeDepth = 0.5;
zField = {}

For[rPos = 0, rPos<=(2 N[Pi]), rPos += radiusInc,
       zPotential = 0;
       Print@ToString@rPos;
       xPos = rDistance Cos[rPos];
       yPos = rDistance Sin[rPos];
       zPos = planeDepth;
       AppendTo[zField, {xPos,yPos, zPotential}];
       Print@ToString@Length[zField] 
    ];

The Print statements show no output. When I step into the loop in the Wolfram Workbench, the only line executed is:

zPotential = 0;

The debugger hits this line twice and falls out. It does not appear that rPos is incremented, although the value of radiusInc is 0.31415...

Also - if I transpose the first two lines in the body of the For[] - so that the Print@ToString@rPos precedes the assignment of zPotential as shown below, the debugger does not hit the Print@ToString@rPos and no output is produced. Oddly it goes to the zPotential=0; line and loops back to the For[]:

For[rPos = 0, rPos<=(2 N[Pi]), rPos += radiusInc,
       Print@ToString@rPos;
       zPotential = 0;
       xPos = rDistance Cos[rPos];
       yPos = rDistance Sin[rPos];
       zPos = planeDepth;
       AppendTo[zField, {xPos,yPos, zPotential}];
       Print@ToString@Length[zField] 
    ];

This one has me completely stumped.

Changing to a While[] loop produces the same result.

rPos = 0; 
MAXRPOS = (2 N[Pi]);
While[rPos<=MAXPOS, 
    Print@ToString@rPos;
    zPotential = 0;
    xPos = rDistance Cos[rPos];
    yPos = rDistance Sin[rPos];
    zPos = planeDepth;
    AppendTo[zField, {xPos,yPos, zPotential}];
    Print@ToString@Length[zField];
    rPos += radiusInc  
];

Once again, the first line in the body that the debugger hits is zPotential=0; This line is hit twice and the loop is exited.

This is true but radiusInc is initialized to N[Pi]/10 or 0.31415926...

Please post self contained complete working/not-working example. You have values in your example that are not defined before the loop starts. The code posted should be in one cell that one can copy and paste and run. Showing a fragment of the code makes it hard to guess what you had before it.