OpenEuphoria

Re: Suggestion for conditional loops

• Posted by Jason Gade <jaygade at yahoo.com> Jul 15, 2005
• 471 views

Juergen Luethje wrote:
> 
> Hi all,
> 
> I'd like to suggest a new syntax for conditional loops:
> 
> Use "loop" or something similar (rather than "end while") to denote the
> end of a conditional loop, also allow conditional loops without a while
> statement. So the basic conditional loop would look like:
>    do
>       <command_1>
>       <command_2>
>       ...
>    loop
> 
> rather than currently
>    while 1 do
>       <command_1>
>       <command_2>
>       ...
>    end while
> 
> 
> Then allow a while statement at the beginning *or at the end* of the
> loop:
>    while x < 2 do
>       <command_1>
>       <command_2>
>       ...
>    loop
> 
> 
>    do
>       <command_1>
>       <command_2>
>       ...
>    loop while x < 2
> 
> 
> The advantage is in the last case, where we currently have to write:
>    while 1 do
>       <command_1>
>       <command_2>
>       ...
>       if x >= 2 then
>          exit
>       end if
>    end while
> 
> 
> The problems concerning compatibility are little, we just would have to
> replace "end while" with "loop" in existing programs.
> 
> But I don't know whether this would require big changes in the parser.
> Also, we now always have "end <keyword>" (end if, end for, end function, ...).
> Using "do/loop" instead of "while/end while" would introduce an
> exception, so I don't know whether this actually ia good idea. But at
> least I wanted to tell you for discussion.
> 
> Regards,
>    Juergen
> 
> -- 
> Have you read a good program lately?
> 
> 

Yes, Euphoria could use a loop with the test at the end so that it runs at least
once.  But I don't think it will be implemented.

One way of doing it currently instead of using exit is:

-- example from wc.ex
ch = getc(FILE)

while ch != EOF do

    -- some logic to count lines, words, chars
    ch = getc(FILE)

end while

The problem of course is that if you make any changes to the variable
expression, you have two lines to change instead of one.

C'est la vie with Euphoria.



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