Re: Loops (was Re: do { quit; } else { })

On 15/04/2025 20:07, Scott Lurndal wrote:

bart <bc@freeuk.com> writes:

On 15/04/2025 14:19, Kaz Kylheku wrote:

 

Thats's fine. But it means a real 'for' loop doesn't exist in C; you
have to emulate it using that 3-way construct, which is naff, and also
error prone.

 Real for loops _are_ a three-way construct.
 135 FOR I=1 TO 10 STEP 2                              [BASIC]
      for(i = 1; i < 11; i += 2)                        [C/C++]
      do 1 = 1, 10, 2                                   [FORTRAN]

Any step other than 1 is unusual. So Basic and Fortran would typically be:
     for i = 1 to 10     # 6 tokens; Basic
     do  i = 1, 10       # 6 tokens; Fortran
     for i = 1, 10       # 6 tokens; Lua
     for i to 10 do      # 5 tokens; Mine (using default start)
     to 10 do            # 3 tokens; Mine (when index is not needed)
Let's look at that C again:
     for (int i = 1; i < 11; i += 1)  # 15 tokens; C
* I've added 'int' for the C, as most of the above don't need a
   declaration for the loop index. But it will still be 14 without
* I use += for the increment because you did. ++ saves one token,
   but it's still at 13/14 tokens
* All the above can directly use 10 as the upper bound; C has to use
   11 when written idiomatically
Even using a step of two, that would only add 2 tokens to the above; C will still need 14/15 tokens.
Note that C's for-loop is dumb; it merely take three expressions A B C that can be completely unrelated, and arranges them into a loop:
   A; while (B) {...; C}

SPRITE also had:
     UNTIL done, notfound
    DO
        ...
        IF token = "this"
        THEN LOOP_EXIT done
        FI;
        ...
        IF i = upb(table)
        THEN LOOP_EXIT notfound
        FI;
        ...
    OD
    CASE
    IS done:     write("i=", i);
    OR notfound  write("not found", upb(table));

That's pretty weird, but whatever it does, it's nothing to do with iterating a variable over a range.