charIndex property

[Paul Dupuis]

Bob,

Here is a version of Mark's method, for trueWords, sentences, and 
paragraphs, with the added parameter of pDirection to get the char index 
of the start of the chunk or the end of the chunk containing the 
character position pChunkIndex.

*private**function* rwCharIndex pText, pChunkType, pChunkIndex, pDirection

*-- pText is the full text*

*-- pChunkType is once of: words|sentences|paragraphs*

*-- pChunkIndex is the integer index in the indicated units. ie. 
"word",7 is the 7th word*

*-- pDirection is one of: first|last meaning either the 1st character of 
the chunk or the last character*

*-- error checking, emty is returned if an error occurs with the parameters*

*if* pText isempty*then* *return*empty

*if* pChunkType isnotamongtheitemsof"words,sentences,paragraphs"*then* 
*return*empty

*if* pChunkIndex isnotaninteger*then* *return*empty

*if* pDirection isnotamongtheitemsof"first,last"*then* *return*empty

*local*tL

*switch* pChunkType

*case* "words"

*switch* pDirection

*case* "first"

*put*nullintotrueWordpChunkIndex to-1 ofpText

*put*codeunitOffset(null,pText) intoN

*delete*codeunitN to-1 ofpText

*return*(thenumberofcharsinpText + 1)

*break*

*case* "last"

*put*length(trueWordpChunkIndex ofpText) intotL

*put*nullintotrueWordpChunkIndex to-1 ofpText

*put*codeunitOffset(null,pText) intoN

*delete*codeunitN to-1 ofpText

*return*(thenumberofcharactersinpText + tL)

*break*

*end* *switch*

*break*

*case* "sentences"

*switch* pDirection

*case* "first"

*put*nullintosentencepChunkIndex to-1 ofpText

*put*codeunitOffset(null,pText) intoN

*delete*codeunitN to-1 ofpText

*return*(thenumberofcharsinpText + 1)

*break*

*case* "last"

*put*length(sentencepChunkIndex ofpText) intotL

*put*nullintosentencepChunkIndex to-1 ofpText

*put*codeunitOffset(null,pText) intoN

*delete*codeunitN to-1 ofpText

*return*(thenumberofcharactersinpText + tL)

*break*

*end* *switch*

*break*

*case* "paragraphs"

*switch* pDirection

*case* "first"

*put*nullintoparagraphpChunkIndex to-1 ofpText

*put*codeunitOffset(null,pText) intoN

*delete*codeunitN to-1 ofpText

*return*(thenumberofcharsinpText + 1)

*break*

*case* "last"

*put*length(paragraphpChunkIndex ofpText) intotL

*put*nullintoparagraphpChunkIndex to-1 ofpText

*put*codeunitOffset(null,pText) intoN

*delete*codeunitN to-1 ofpText

*return*(thenumberofcharactersinpText + tL)

*break*

*end* *switch*

*break*

*end* *switch*

*end*rwCharIndex




On 7/31/2023 11:44 AM, Bob Sneidar via use-livecode wrote:
> I replaced the code in the original function with this code and it won’t compile.
>
> Do you mind posting the full working function again?
>
> Bob S
>
>
>> On Jul 27, 2023, at 2:06 PM, Mark Waddingham via use-livecode <use-livecode at lists.runrev.com> wrote:
>>
>> Oh those pesky chunks which don’t ‘cover’ the target string (which is actually all of them except codeunit/point/char come to think of it). I should have run through a few more examples in my head before posting….
>>
>> Alternative attempt:
>>
>> Put null into word N to -1 of S
>> Delete codeunit (codeunitoffset(null, S) to -1 of S
>> Return the number of chars in S + 1
>>
>> The problem before was the chars which do not form part of the last chunk and remain after deletion.
>>
>> The above puts in a sentinel char which can be searched for to find where the requested chunk started.
>>
>> Second time lucky? ;)
>>
>> Mark.
>>
>> Sent from my iPhone
>>
>>> On 27 Jul 2023, at 21:23, Paul Dupuis via use-livecode <use-livecode at lists.runrev.com> wrote:
>>>
>>> On 7/27/2023 4:31 AM, Mark Waddingham via use-livecode wrote:
>>>>> On 2023-07-26 18:02, Paul Dupuis via use-livecode wrote:
>>>>> If I have some text in a field, I can use the "charIndex" property (see Dictionary) to obtain teh character position of the first character of a chunk.
>>>>>
>>>>> Does anyone know of a clever way to do the equivalent of the charIndex for an arbitrary chunk expression for a container/variable (i.e. not an actual field object)?
>>>> This should work I think:
>>>>
>>>>    function charIndexOfWord pWordIndex, pTarget
>>>>       delete word pWordIndex to -1 of pTarget
>>>>       return the number of characters in pTarget + 1
>>>>    end charIndexOfWord
>>>>
>>>> Deletion of chunks works from the first char that makes up the computed range, so you are left with all the characters which sit before it.
>>>>
>>>> The index of the character immediately before the start of the specified word is the just the number of characters which sit before it; and so the index of the first char of the specified word (which is what charIndex gives you in a field) is that +1.
>>>>
>>>> The above should work for both +ve and -ve indices, and the obvious changes will make it work for other string chunks (i.e. change 'Word' for <chunk>).
>>>>
>>> Mark,
>>>
>>> Thank you very much. This was a brilliant approach and I should have thought of it myself. However, it is not quite an accurate substitute for the charIndex property of a field. The following example illustrates the issue:
>>>
>>> pTarget is [The quick brown fox jumps over the lazy dog. The lazy dog was named "Oz".]
>>> pWordIndex is 8 (having been derived from searching for 'lazy', the 8th word)
>>>
>>> Using [] to quote strings.
>>> delete word 8 to -1 of pTarget -- deletes [lazy] to ["Oz"] but not the period (.) at the end since it is not considered part of word -1.
>>> This leaves pTarget as [The quick brown fox jumps over the .]
>>> The number of characters in pTarget + 1 is actually not the position of the [l] in [lazy], which is character 36, but the [a] in [azy], character 37, due to the period being left.
>>>
>>> There are some similar issues, being off by  or more, with sentences and paragraphs in longer text.
>>>
>>> Thank you very much for chiming in with a good direction to try.
>>>
>>> Paul Dupuis
>>> Researchware
>>>
>>>
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>>
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