Failing to understand the oddities of the "line" chunk

[Alex Tweedly]

You're right (IMHO) - the original reason I struggled to understand this 
was not the trailing delimiter issue, but rather the incorrect handling 
of 'inverted' ranges in a chunk expression.

There are a variety of possible valid interpretations of a inverted 
range (my opinion is that these are, in order):

1. normalize the order (as you suggested)
      (i.e. put xxx into line  3 to 2 ... would be equivalent to put xxx 
into line 2 to 3 ...)
2. take the "from" part of the chunk range expression, and stop there
      (i.e. put xxx into line  3 to 2 ... would be equivalent to put xxx 
into line 2 ...)
3. cause an error !!??

What it does now is (I think) equivalent to
      put xxx before line 3 of ....
Which is consistent to viewing
    put xxx into (chunk) of (container)
as being equivalent to
    put xxx before line tFROM of container
    repeat with i = tFROM to tTO of container
       delete line i of (the original) container
   end repeat

So I can just about see that there is some consistency in the current 
method - but it is highly unintuitive and hard to predict.

-- Alex.

On 17/03/2012 20:31, Geoff Canyon wrote:
> This seems wrong to me. Regardless of how the engine interprets a chunk
> expression, a command of the form put<something>  into<some chunk>  should
> result in<some chunk>  containing<something>  So the fact that you are
> putting "b" into something should result in that thing being "b," where
> here the result is "ba" further, there's the fact that after the command,
> the chunk is still empty. So:
>
>   put "a"&  cr into t;put "b" into line 2 to -1 of t;put line 2 to -1 of t
> is empty
>
> puts true. I did a quick check to take the negative line number out of
> this. If you have a field with contents:
>
> a
>
> b
>
> c
>
> then put line 2 to 1 of fld 1
>
> puts empty, and put "x" into line 2 to 1 of fld 1
>
> results in line 1 of the field being "xa"
>
> again, this feels wrong. "line 2 to 1" of something should be an error. I
> can see the value of having it return empty when you are getting it, but
> putting something into it results in bad behavior.
>
> Another way of addressing this would be to say that chunk expressions
> always understand and follow proper order. So "line 2 to 1" would be the
> same as "line 1 to 2" Under that scenario, put "x" into line 2 to 1 of fld
> 1 would result in the field containing:
>
> x
>
> c
>
> and the original problem:
>
> put "a"&  CR into t; put "b" into line 2 to -1 of t; put t
>
> would put
>
> b
>
> which seems like a much more reasonable (and predictable) outcome.
>
>
> gc
>
> On Sat, Mar 17, 2012 at 11:33 AM, J. Landman Gay
> <jacque at hyperactivesw.com>wrote:
>
>> On 3/17/12 8:16 AM, Alex Tweedly wrote:
>>
>>> This code
>>>
>>>> put "a"&  CR into t; put "b" into line 2 of t; put t
>>>>
>>> produces (as I would expect)
>>>
>>>> a
>>>> b
>>>>
>>> BUT
>>>
>>>> put "a"&  CR into t; put "b" into line 2 to -1 of t; put t
>>>>
>>> produces
>>>
>>>> ba
>>>>
>>> Why should adding the "to -1" change this to put the new data before
>>> what was there before ?
>>>
>> It's because of how the engine ignores trailing delimiters. The variable t
>> contains only one line, so "line 2 to -1" evaluates to "line 2 to 1".
>>
>> --
>> Jacqueline Landman Gay         |     jacque at hyperactivesw.com
>> HyperActive Software           |     http://www.hyperactivesw.com
>>
>>
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