On Jan 20, 3:36 pm, TonyLanz <tolan...@gmail.com> wrote:
> Hi all,
> I realize this has been asked on the group before. I'm hoping someone
> might have a "simple" workaround in IDLVM to what would be easily
> accomplished using the execute function in IDL proper. I have a widget
> program that contains a compound widget field that allows the user to
> define an equation for manipulating a set of four variables. For the
> sake of argument let's say var1, var2, var3, and var4. In this
> compound widget field they can define what math they want to do,
> they're restricted to addition, subtraction, multiplication and
> division.
>
> so they could for example enter
>
> var1/var2
> or
> var1-var2*0.2
> or
> var1+var2+var3
>
> etc., you get the idea. Now in IDL I can just get the value from the
> widget and simply do something like
>
> s='result='+cwidget_value(0)
> status=execute(s)
> print,result
>
> of course in IDLVM I'm not allowed to use EXECUTE()
>
> Anyone have any suggestions for implementing this simply? I know in
> the past there was discussion of writing code to break down the string
> and pass the pieces to the right operators or functions (using
> call_function() ) to assemble the result.
>
> Tony
Yes, like all things, there are several ways to skin this cat. The
simplest way is to write the string to a file, compile that file, then
call it as a function (and presumably delete it after you're
finished). So if you have the command as a string, such as "result =
var1 + var2*0.2" then just write it to a file with the appropriate
declarations and closings. So, you'd execute:
;save the data:
vars=[var1,var2]
;write the file:
openw,lun,'file.pro',/get_lun
printf,lun,'function file,vars'
printf,lun,'return,vars(0)+vars(1)*0.2'
printf,lun,'end'
close,lun & free_lun,lun
;compile the file
resolve_routine,'file.pro',/is_function
;call the function:
result=call_function('file',var1,var2)
;clean up
file_delete,'file.pro',/allow_non
now the rub here is that you need to know how many variables there are
to store in that temporary variable. Hopefully, there's some way for
you to loop over that.
The alternative way, would be to parse the command using the usual
order of operations rules. Then process that parsed things using pre-
defined functions for the four arithmetic operations. Such as:
t=multiply(v1,v2)
t=divide(v1,v2)
etc. WHere they have the obvious "innards". Of course, this can get
very tedious, but is very useful. If you go down this path, I
recommend using the byte typecasting to find the major operators:
t=byte(cmd).
Good Luck
Russell
PS, the reason this is so complicated, is that they don't want you
doing this.
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