case expression

mikea

Hi, I'm trying to use case to test 3 values for not equal to x. If 4 is not equal to x, then dira[4]~ and so on. The compiler wants to see an expression term and highlights "<>". I'm not clear on what an expression term is. Thanks

case  <> x
   4: dira[4]~
   5: dira[5]~
   6: dira[6]~

Peter Jakacki

mikea wrote: »

Hi, I'm trying to use case to test 3 values for not equal to x. If 4 is not equal to x, then dira[4]~ and so on. The compiler wants to see an expression term and highlights "<>". I'm not clear on what an expression term is. Thanks

case  <> x
   4: dira[4]~
   5: dira[5]~
   6: dira[6]~

That's a back to front case statement if I've seen one. Just supply the argument to case as x ( case x ) then that should work. However you could just as easily say:
if x <> 4 or x <> 5 or x <> 6
do this

But I see you probably need a case statement because of the different actions but I'm not getting the mixed up logic of this operation as if x <> 4 could just as easily be x <> 5 ..... oh well.

tonyp12

Case is like TEST, you ask it for a RESULT, you can have calculation at the time that don't get writing back to X, our just simple: case X

case X+Y
3:do that
4:or this
5:maybe this
other: do this for everything else

ChrisGadd

The case expression can only be a single value, not a range.
You can test ranges in the match expressions however, so you could do:

  case x
    1..3,5..10 : dira[4]~
    1..4,6..10 : dira[5]~
    1..5,7..10 : dira[6]~

However, that probably doesn't do what you were expecting either, as case stops at the first match. If x were 7 for instance, only pin 4 would be set to an input.
You could work around that by creating something like:

  case x
    1..3,7..10    : dira[4..6]~
    1..3,6..10    : dira[4..5]~
    1..3,5,7..10 :
      dira[4]~
      dira[6]~
    1..4,7..10    : dira[5..6]~

or use if / thens as in:

  if x <> 4
    dira[4]~
  if x <> 5
    dira[5]~
  if x <> 6
    dira[6]~

Or simply set every pin other than x in a range to an input, and leave x unchanged: dira := |< x & dira | dira &! %01110000

Alexander (Sandy) Hapgood

mikea wrote: »

Hi, I'm trying to use case to test 3 values for not equal to x. If 4 is not equal to x, then dira[4]~ and so on. The compiler wants to see an expression term and highlights "<>". I'm not clear on what an expression term is. Thanks

case  <> x
   4: dira[4]~
   5: dira[5]~
   6: dira[6]~

The case statement requires an 'expression term' it can evaluate to a single value.

a := 4
case a
  1..4 : b := 5
     5 : b := 6
     6 : b := 7

If there's only three values you could use a series of if statements

value1 := 1
value2 := 2
value3 := 3
x := 2
if value1 <> x
   dira[ value ]~
if value2 <> x
   dira[ value2 ]~
if value3 <> x
   dira[ value3 ]~

Sandy