Re: else ladders practice

Bart wrote:

On 04/11/2024 15:06, fir wrote:

fir wrote:

Bart wrote:

On 04/11/2024 04:00, Tim Rentsch wrote:

fir <fir@grunge.pl> writes:
>

Tim Rentsch wrote:

>

With the understanding that I am offering more than my own opinion,
I can say that I might use any of the patterns mentioned, depending
on circumstances.  I don't think any one approach is either always
right or always wrong.

>
maybe, but some may heve some strong arguments (for use this and not
that) i may overlook

>
I acknowledge the point, but you haven't gotten any arguments,
only opinions.

>
Pretty much everything about PL design is somebody's opinion.

>
overally when you think and discuss such thing some conclusions may do
appear - and often soem do for me, though they are not always very clear
or 'hard'
>
overally from this thread i noted that switch (which i already dont
liked) is bad.. note those two elements of switch it is "switch"
and "Case" are in weird not obvious relation in c (and what will it
work when you mix it etc)
>
what i concluded was than if you do thing such way
>
>
a {  }  //this is analogon to case - named block
b {  }  //this is analogon to case - named block
n()   // here by "()" i noted call of some wariable that mey yeild
'call' to a ,b, c, d, e, f  //(in that case na would be soem enum or
pointer)
c(  ) //this is analogon to case - named block
d(  ) //this is analogon to case - named block
>
>
then everything is clear - this call just selects and calls block , and
block itself are just definitions and are skipped in execution until
"called"
>
>
this is example of some conclusion for me from thsi thread - and i think
such codes as this my own initial example should be probably done such
way (though it is not c, i know
>
>

note in fact both array usage like tab[5] and fuunction call like foo()
are analogues to swich case - as when you call fuctions the call is
like switch and function definition sets are 'cases'
>

>
Yes, switch could be implemented via a table of label pointers, but it
needs a GNU extension.
>
For example this switch:
>
  #include <stdio.h>
>
  int main(void) {
    for (int i=0; i<10; ++i) {
        switch(i) {
        case 7: case 2: puts("two or seven"); break;
        case 5:         puts("five"); break;
        default:        puts("other");
        }
    }
  }
>
>
Could also be written like this:
>
  #include <stdio.h>
>
  int main(void) {
      void* table[] = {
          &&Lother, &&Lother, &&L27, &&Lother, &&Lother, &&L5,
          &&Lother, &&L27, &&Lother, &&Lother};
>
      for (int i=0; i<10; ++i) {
          goto *table[i];
>
          L27:    puts("two or seven"); goto Lend;
          L5:     puts("five"); goto Lend;
          Lother: puts("other");
          Lend:;
      }
  }
>
(A compiler may generate something like this, although it will be
range-checked if need. In practice, small numbers of cases, or where the
case values are too spread out, might be implemented as if-else chains.)
>
>

probably swich is implemented like
  push __out__  //to simulate return under out_ adress
  cmp eax, "A"
  je __A__
  cmp eax, "B"
  je __B__
  cmp eax, "C"
  je __C__
__out___:
...
...
...
if elkse ladder would do the same i guess
and sequence f ifs  would not push __out__ if
not detected it can ans those cases for sure may not appear
its waste to check a long sequance of compares it someones unlucky
though if the argument of switch is like 8bit wide it is probably no
problem to put the labels in the teble and callvia the table