Case-logic

27 Oct 2004


      On Tue, 26 Oct 2004 19:26:02 -0700 (PDT), Chris Muller  
afu.nkyobject@yahoo.com wrote:
...
I don't see any harm in case-logic for checking hot keys..
I've been meaning to ask the group this, since I remember picking up the  
anti-case message from Meyer (coincidentally enough, in his Eiffel books)  
but I'm trying to figure out how I'd program a state machine without it.  
Well, I can see how to do it, but I don't think I "get it" since it  
doesn't seem easier or clearer to do it that way.
Can anyone recommend some state-machine type stuff in the codebase for me  
to look at? Or thoughts on how you'd code something like the code below?
(Some background: I'm writing a book for kids on programming. I learned to  
program in Basic and despite the fact that it gave me a strong taste for  
finding better ways of doing things, I really don't want to inflict that  
on another generation.<s> That means, in part, rooting out my own bad  
habits so as not to pass them on.)
===Blake===
WHILE (i<=len(expr))
    IF c>="A" and c<="Z" THEN 'we're at a function call
    ...
    ELSE IF C="[" THEN 'we're at a user defined variable
    ...
    ELSE IF C="_" THEN 'we're at a system value
    ...
    ELSE IF at("operator", expect)>0 and at(C, "+-*/<=>")>0 THEN 'operator
    ...
    ELSE IF at(c+d, ".A.O.N") > 0 THEN 'logical operator
    ...
    ELSE IF at(C, numeric)>0 or ((C="-" .or. D="+") and at(D, numeric)>0)  
THEN 'we're at a literal constant
    ...
    ELSE IF C = "," THEN
    ...
    ELSE IF C="(" THEN 'we're grouping terms or in a procedure
    ...
    ELSE IF C=")" THEN 'we're ending a group of terms
    ...
    ELSE IF C=" " THEN 'ignore spaces
    ...
END WHILE