OpenEuphoria

1. What is process_lines? and general complaint on the new manual

• Posted by lionel Jan 19, 2011
• 2145 views

Hi everyone, longtime Euphoriac here just getting started with 4.0.

I'd like to know, what is process_lines() for and how to use it?

I'm confused by the example given in the manual. process_lines() is a function yet in the example there is no result assigned, as if it was a procedure.

...

In general, the new manual does not clearly show what a function returns. The Eu3.x manual showed this easily, like so:

    Syntax: s2 = append(s1, x) 

We see at a glance that append() takes a sequence and an object and returns a sequence, and then a detailed explanation followed.

I wish the manual could be like this. An html version rather than (or in addition to) a pdf would be nice too.

Thanks for reading.

Lionel

3. Re: What is process_lines? and general complaint on the new manual

• Posted by ChrisB (moderator) Jan 19, 2011
• 2131 views

Hi

It used to be that all functions required a return value, or else an error would be thrown. Now, when you call a function, you don't need a return value, so

 
function foo() 
 
return 1 
end function 
 
integer x 
x = foo()  -- ok eu 3.xx, and 4.xx 
 
foo() --throws and error with eu3, but is ok with 4 
 

Kind of makes the procedure redundant, makes no real difference with speed (AFAIK), and seems to be being maintained for backwards compatability.

On the subject of the manual, I find it readable, and clear (see the section where it says 'Returns :'), I think the problem is with the explanation of the function itself. I would probably avoid it myself (personally), as, for me, it reduces clarity of the code (others may / will disagree). Perhaps a 'simpleton' (stress for the likes of me too!) explanation would be of benefit. To me, the example is not of much help.

-- Format each supplied line according to the format pattern supplied as well. 
function show(sequence aLine, integer line_no, object data) 
  writefln( data[1], {line_no, aLine}) 
  if data[2] > 0 and line_no = data[2] then 
  	return 1 
  else 
  	return 0 
  end if 
end function 
-- Show the first 20 lines. 
process_lines("sample.txt", routine_id("show"), {"[1z:4] : [2]", 20}) 
                                                --^^^^^^^^^^^^^^^^^^ a better explanation of this 

The function show(), seems to be writing to a file, rather than showing it, and where does the 'first 20 lines' come from?

Chris

5. Re: What is process_lines? and general complaint on the new manual

• Posted by ne1uno Jan 20, 2011
• 1898 views

often you will see the function return assigned to a VOID or JUNK object and then never used. sometimes it is simpler to just ignore the return of an error value.

the error return of process_list() is what the caller of the function decides it is. this would probably be used in a real program, but you can also observe the output of those 20 lines to decide if there were an error. but is just an example.

filter() or build_list() could return such a modified sequence.