Flesxible looping [Was: Making Revolution faster with really big arrays]

Wed Apr 13 11:33:27 EDT 2005

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People working on computer languages generally avoid (and with good 
reason) adding new keywords.

Have you considered "and for" rather than "also"?

On Apr 13, 2005, at 11:25 AM, Alex Tweedly wrote:

> Dennis Brown wrote:
>
>> The Idea is to break apart the essential functional elements of the 
>> repeat for each control to allow more flexibility.  This sample has a 
>> bit more refinement than what I posted yesterday in Bugzilla.
>>
>> The new keyword would be "access" , but could be something else.
>>
>> An example of the use of the new keywords syntax would be:
>>
>> access each line X in arrayX--initial setup of pointers and X value
>> access each item Y in arrayY --initial setup of pointers and Y value
>> repeat for number of lines of arrayX times --same as a repeat for each
>>    put X & comma & Y & return after ArrayXY --merged array
>>    next line X --puts the next line value in X
>>    next item Y --if arrayY has fewer elements than arrayX, then empty 
>> is supplied, could also put "End of String" in the result
>> end repeat
>>
>> Another advantage of this syntax is that it provides for more 
>> flexibility in structure of loops.  You could repeat forever, then 
>> exit repeat when you run out of values (based on getting an empty 
>> back).  The possibilities for high speed sequential access data 
>> processing are much expanded which opens up more possibilities for 
>> Revolution.
>
>
> Dennis,
>
> I think having more flexible repeat structures to allow parallel 
> passes through lists or arrays is a really good idea, but I don't like 
> the form you have suggested. It seems wrong to have separate 
> statements to setup the loop; as far as I know, the language currently 
> keeps the meaning of each statement self-contained, so I think this 
> multi-line form would be a hard one to "sell".
>
> I think it would be better to add a new keyword to indicate parallel 
> looping; the primary loop determines the repeat-termination test 
> criterion, while the others are incremented/advanced in synch. (of 
> course, using exit allows you to terminate the loop based on the 
> secondary loops if needed).
>
> I'd suggest the word "also" since it's not currently used, or perhaps 
> the phrase  "also each".
>
> So the form would be something like
>
>> repeat for each line X in xList also item Y in yLine  repeat for each 
>> line X in xList also each item Y in yLine  repeat for each line X in 
>> xList and also each item Y in yLine
>
> and of course there could be more than 2 :
>
>> repeat for each line Y in ylist also line x in xlist also item z in 
>> zlist also item name in        namelist ...
>
>
> This would allow the variants
>
>> repeat forever also each item Z in theList
>> repeat for each element E in myArray also each line X in xList
>> repeat with i = 1 to 100 also each line X in xList
>
> etc.
>
>
> And for symmetry, it might also be feasible to allow
>
>> repeat for each X in Xlist also i = 1 step 1
>
> (since there's not a terminating condition in the secondary, it would 
> confusing to have i = 1 to 100, so simply specify initial and step 
> values).
>
>
> Similar to this, I'd love to see a method for accessing arrays which 
> gives both the key and the element. Currently, you can say
>   repeat for each line K in the keys of myArray
>     put myArray[k] into V
> but most modern languages have something like
>   for (k,v in myarray)
> which gives both key and value without needing to do another hash 
> lookup.
>
> And now that I'm started on this topic, I've always envied the 
> readability of Python's tuple-assignment. I find
>   x1,y2,x2,y2 = myRectangle
> much more obvious than
> x1 = myRectangle[0]
> y1 = myRectangle[1]
> x2 = myRectangle[2]
> etc.
>
> In Transcript, I really wish I could say
>   put myRectangle as items into x1,y1,x2,y2
> or
>   put the items of myRectangle into x1,y1,x2,y2
> instead of the clumsy
>  put item 1 of myRect into X
>  put item 2 of myRect into Y
> etc.
>
> No performance advantage - but so much more readable.
>
> -- 
> Alex Tweedly       http://www.tweedly.net
>
>
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- -----------------------------------------------------------
Frank D. Engel, Jr.  <fde101 at fjrhome.net>

$ ln -s /usr/share/kjvbible /usr/manual
$ true | cat /usr/manual | grep "John 3:16"
John 3:16 For God so loved the world, that he gave his only begotten 
Son, that whosoever believeth in him should not perish, but have 
everlasting life.
$
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