Parameter checking

[Sarah Reichelt]

Hi All,

I have a stack that contains a set of commands for talking to a  
serial device. The commands & functions all get a set of parameters,  
each with only one character. The characters vary: some parameters  
are numeric, some alphabetic. The ranges vary, so one parameter could  
be any letter from A to N while another can be either J, T or E.  
Numeric parameters have allowed ranges also. As you can imagine,  
sending the wrong info to the serial box causes big problems.

What I am thinking of doing is writing a general parameter checker,  
so I can send it each parameter, plus some string defining what is  
allowed. If it returned an error, then I would refuse to send the  
command to the serial box.

Firstly, has anyone done anything like this? If so, would they be  
prepared to share the code or some of their ideas.

Secondly, has anyone any suggestions of the best way to do this? I  
can do it in a long-winded manner, but I feel sure that some RegEx  
wizard (Ken, are you listening), would be able to come up with a  
really neat way to solve this.

Here is pseudo-code is what I want to do:

on sendSerialCommand p1, p2, p3
   -- p1 must be A-P or a-p
   if paramError(p1,"A-P|a-p") then exit to top
   -- p1 must be a number from 1 to 8
   if paramError(p2,"1-8") then exit to top
   -- p1 must be either S or D
   if paramError(p3,"S|D") then exit to top

   sendSerialString p1 & p2 & p3
end sendSerialCommand

TIA,
Sarah