Re[2]: [Ficl-developers] Here's a 'switch' implementation for FICL

[David M. <da...@re...>]

Hi john,

js> I _do_ like it. A couple things I'd like to try to improve:
js> 1. As implemented, all conditionals are executed for every pass through the 
js> switch, even if
js> one matches early. I think I can add a simple trick that gets around that 
js> problem.

Not too severe a problem, because:
1) The conditionals are getting executed, but the user code between
each 'case'...'break' pair is not executed unless there's a match.
So the implementation as it stands is working fine.

2) As it is, it would not be noticeably slower than a chain of
'if...endif' or 'if...else...endif' statements that people would have
to use if 'switch' isn't available.

3) I'd advise against any strategy which executes the user code inside
a matching conditional then jumps to the end of the switch. Even 'C'
doesn't do that.

Example:

variable var1
variable var2
variable n

...

[some calculations which alter var1, var2 and/or n]

n @ switch
  0 case
     some user code
     break
  1 case
     some user code
     break
  var1 @ case
     some user code
     break
  var2 @ case
     some user code
     break
endswitch

As you can see from this example, a programmer may deliberately want
case statements which are not mutually exclusive, which is accepted
practice in 'C'. If you implement a dropout at the end of executing a
matching case, the code will fail.

If you want to implement mutual exclusivity (can be desirable for
speed reasons), I'd advise a separate word, say, 'switch-ex'.

David