OpenEuphoria

Re: Switch question - yet again!

• Posted by _tom (admin) Sep 28, 2016
• 11298 views

There is a mystery here which I can't explain.

Example 1 // works

include std/stack.e 
 
constant op = 1 
    ? op 
    --> 1 
 
 
integer stk = op 
    ? stk 
    --> 1 
 
    switch stk do 
        case op then 
            puts(1, "\n result is first stack \n" ) 
        case else 
            puts(1, "\n result is something else \n") 
    end switch 
 
--> result is first stack 

Example 2 // fails

include std/stack.e 
 
 
constant op = stack:new(FIFO) 
    ? op 
    --> 1 // "stacks" start numbering at one 
 
integer stk = op 
    ? stk 
    --> 1 
 
    switch stk do 
        case op then 
            puts(1, "\n result is first stack \n" ) 
        case else 
            puts(1, "\n result is something else \n") 
    end switch 
 
--> machine level exeception 

Since "op" is a constant, in theory it should work in a switch statement--but it fails.

Example 3 // works

include std/stack.e 
 
constant op = stack:new(FILO) 
    ? op 
    --> 1    // "stacks" start numbering at one 
 
stack:push(op, 23 ) 
    ? stack:peek_top(op) 
    --> 23   // value at top of "op" stack 
 
show_stack( op ) 
 
procedure show_stack( integer stk ) 
 
    puts(1, "\n executing show_stack \n" ) 
    ? stk 
    ? op 
 
-- this does work 
 
    if equal(stk,op) then 
        puts(1, "\n result is first stack \n" ) 
    else 
        puts(1, "\n result is something else \n" ) 
    end if 
 
end procedure 
 
--> result is first stack 

_tom