OpenEuphoria

1. add_item question

• Posted by Aveu Sep 24, 2012
• 1620 views

According to the documentation for the add_item procedure (as well as the append procedure which it relies on) the parameter needle is an object and the parameter haystack is a sequence. Going strictly off the documentation I would expect the following to work but it does not:

sequence theList = {} 
sequence theWord = "test" 
add_item(theWord,theList,ADD_SORT_UP) 

Even enclosing theWord in curlybraces (which should not be necessary) does not help.

Also, there is absolutely no way to tell if the item was added or ignored by the call itself (meaning this procedure really ought to be a function with a results flag returned) meaning this function could really use some kind of function exit status code mechanism.

3. Re: add_item question

• Posted by Aveu Sep 24, 2012
• 1575 views

OK, obviously I have had a brain fart, it is a function not a procedure. I have no clue how that got mixed up in my head. But as to the main issue can anyone help ?

5. Re: add_item question

• Posted by Aveu Sep 24, 2012
• 1573 views

Well, it would appear then that there must be something "subtle" (aka "obvious") wrong with my code that I do not understand. I am an old programmer learning a new language. I ran with trace and things looked good right up to the add_item line but the result was an empty sequence.

As a learning exercise I am writing an anagram solver and the following is my code so far. The relevant variables are Jword1 (aka theWord) and Jwords (aka theList):

 
include std/console.e 
include std/io.e 
include std/os.e 
include std/pretty.e 
include std/search.e 
include std/sequence.e 
include std/sort.e 
include std/text.e 
include std/types.e 
 
with batch 
with trace 
 
sequence letters = "txhoefqdueirck" 
integer size = length( letters ) 
sequence tumbler = series( 1 , 1 , size ) 
sequence Jword1 = "" 
sequence Jwords = {} 
integer ccflag = 0 
 
function valid_Jword( sequence TUMBLER ) 
 
	integer ZZ = 0 
	 
	for XX = 1 to size do 
		ZZ += ( length( find_all ( TUMBLER[XX] , tumbler ) ) - 1 ) 
	end for 
 
	return ( ZZ = 0 ) 
	 
end function 
 
function make_Jword( sequence TUMBLERZ )  
 
	integer ZZ 
	sequence JWORD = repeat( "@" , size ) 
 
	for XX = 1 to size do 
 
		ZZ = TUMBLERZ[XX] 
		JWORD[XX] = letters[ZZ] 
 
	end for 
 
	return JWORD 
 
end function 
 
 
-- initialize -- 
 
clear_screen() 
 
letters = upper ( sort( letters ) )   
tumbler[size] -= 1 -- back off last tumbler by 1 to pre-adjust for the very first pass 
 
-- run main process -- 
loop label "loop_AA" do -- until tumbler[1] > size 
	 
	loop label "loop_BB" do -- until a valid Jword is found 
	 
		ccflag = 1 
		for CC = size to 1 by -1 label "loop_CC" do 
			 
			tumbler[CC] += ccflag 
			if tumbler[CC] > size then 
				tumbler[CC] = 1 
				ccflag = 1 
			else 
				ccflag = 0 
			end if 
			 
		end for 
			 
	until valid_Jword( tumbler ) -- end loop_BB 
	end loop 
	 
trace(1) 
	if ( tumbler[1] <= size ) then  
		Jword1 = make_Jword( tumbler ) 
		add_item( Jword1 , Jwords , ADD_SORT_UP )  
	end if 
trace(0) 
 
until tumbler[1] > size	 
end loop 
	 

7. Re: add_item question

• Posted by Aveu Sep 24, 2012
• 1629 views

DOH! Yep, obvious!

OK, so what I learned is that a FUNCTION in Euphoria can be called like a PROCEDURE (not located to the right of an '=' character) without generating an error. Is that in the documentation ?

9. Re: add_item question

• Posted by euphoric (admin) Sep 24, 2012
• 1542 views

That is correct.

The only reference I could find is in 1.3.3 Language Enhancements: "Function results can now be ignored."

There should at least be a comment about it in 4.2.1.2. functions.

11. Re: add_item question

• Posted by jimcbrown (admin) Sep 25, 2012
• 1467 views

In general, true. In the specific case of add_item(), you still do. Calling add_item() but not using the return value is pointless, as add_item() has no side effects.

procedure

return 0

Well, no not really. Getting rid of it would break a lot of code though.

13. Re: add_item question

• Posted by ne1uno Sep 25, 2012
• 1531 views

procedure

return 0

maybe there should be an error when you don't catch the result from a function that the only reason you are calling it is to get the result?

euphoria can't change the sequence from the function call alone. you must catch the result.

15. Re: add_item question

• Posted by EUWX Sep 25, 2012
• 1483 views

procedure

return 0

I agree that the word "catch" is not appropriate in high level discussion of a basic type of language; I should have said "assignment".

The best approach (and I can't think of any language that has it all) would be to have ALL functions/procedures return two results
(which means, of course, that procedures and functions are no different from each other.)
One would be a sequence contain information on error code, location of error etc. This would ALWAYs be available upon exiting from function in a Global variable 'lastcallerror". The other would be the main returned result.
A system variable which is programmer/user settable would allow an OnError module to selectively take over for
1. unpardonable (un-proceedable) error;
2. slightly tolerable error;
3. moderately tolerable level;
4. Warning level error.

Thus, even if an error occurs say at the 200th element (e.g. divide by zero) there would be 199 properly done elements of the new sequence available as argument to the next function SHOULD the programmer want to use them.

Matt et all. It is not difficult at all to change the Euphoria procedures to start returning a null, which the old programs are already ignoring, and the new programs would know what the result is going to be.