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Detecting if a script line has a line continuation character
Posted: Wed Jul 13, 2016 9:45 am
by livecodeali
I'm wondering if anyone has any clever ideas on how to check for a given line of script whether the parser will treat the following line as a continuation.
Currently the script editor uses
Code: Select all
function lineIsContinued pLine
return word -1 of pLine is "\"
end lineIsContinued
which will work in a large number of cases. However, the following bugs are examples where it doesn't:
http://quality.livecode.com/show_bug.cgi?id=8228 (because the \ is followed by a comment)
http://quality.livecode.com/show_bug.cgi?id=8328 (because the last word of
is
Moreover it will not work in the following case
The latter two examples would be fixed using
, but I'm wondering if there's any way that covers all cases.
The char method has issues with this:
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put "a" into tVar --don't continue this line! \
put "b" into tVar2
This is the best I can come up with:
Code: Select all
function lineIsContinued pLine
local tTokens, tFirstChar
put token 1 to -1 of pLine into tTokens
put offset(tTokens, pLine) into tFirstChar
put "get a" into char tFirstChar to tFirstChar + length(tTokens) of pLine
put return & "& b" after pLine
compileCheck pLine
return the result
end lineIsContinued
on compileCheck pScript
local tCompileTest, tCompileResult
--checks to see if the message compiles
lock messages
create script only stack "compilationTest"
put "on compileTest" & cr & pScript & cr & "end compileTest" into tCompileTest
set the script of stack "compilationTest" to tCompileTest
put the result into tCompileResult
delete stack "compilationTest"
unlock messages
return tCompileResult is not empty
end compileCheck
Obviously this is rather heavyweight, and would fail in the case that the actual script occurred in comments:
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/* put "a" into */ put "a" into /* put "a" into */ /
tVar
That example seems to be immune to any further tweaks to finding the offset of the tokens in the original line. Any ideas?
Re: Detecting if a script line has a line continuation chara
Posted: Wed Jul 13, 2016 3:00 pm
by dunbarx
Hi.
I get no errors or issues with your first few examples, all the way up to "this is the best I can come up with...". This is in v6.11.
And this:
Code: Select all
/* put "a" into */ put "a" into /* put "a" into */ /
tVar
really has nothing to do with the line continuation char.
Craig Newman
Re: Detecting if a script line has a line continuation chara
Posted: Wed Jul 13, 2016 5:47 pm
by [-hh]
My idea was wrong, sorry. It's too late in the evening.
Re: Detecting if a script line has a line continuation chara
Posted: Wed Jul 13, 2016 6:17 pm
by dunbarx
Ali.
I did not see it was you, and thought the post was about errors in using that character.
I have no idea what Hermann was upset about.
Anyway, couldn't you still use your "char -1 of word -1..." (I see why you have to check the last word) and also check to see if "--" is in pLine?
The line
contains three words if you simply analyze it as a string, and the last word in any line of line continued code will always have "\" as the last char, or else be improperly formed.
Craig
Re: Detecting if a script line has a line continuation chara
Posted: Wed Jul 13, 2016 6:31 pm
by [-hh]
Hi Craig. Wasn't upset but had a wrong idea which fails if there are quoted comment chars in the line
Re: Detecting if a script line has a line continuation chara
Posted: Wed Jul 13, 2016 8:13 pm
by [-hh]
If comments after a continuation char "\", for example
put "A" into a \ -- just an example
are NOT allowed then one could try the following function:
Code: Select all
function lineIsContinued pLine
replace "\" with ">"&numToChar(1) in pLine
return (token -1 of pLine is numToChar(1))
end lineIsContinued
At least all examples above are correctly handled by that.
Re: Detecting if a script line has a line continuation chara
Posted: Thu Jul 14, 2016 10:48 am
by livecodeali
dunbarx wrote:
And this:
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/* put "a" into */ put "a" into /* put "a" into */ /
tVar
really has nothing to do with the line continuation char.
Oops, put a forward slash there instead of a backslash
Should have been:
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/* put "a" into */ put "a" into /* put "a" into */ \
tVar
[-hh] wrote:If comments after a continuation char "\", for example
put "A" into a \ -- just an example
are NOT allowed then one could try the following function:
Code: Select all
function lineIsContinued pLine
replace "\" with ">"&numToChar(1) in pLine
return (token -1 of pLine is numToChar(1))
end lineIsContinued
At least all examples above are correctly handled by that.
Comments after a continuation char are unfortunately allowed, and it would be breaking backwards compatibility to change that. However I believe the gist of your example could be the most practical solution. It would even work for the other example I just thought of,
Re: Detecting if a script line has a line continuation chara
Posted: Thu Jul 14, 2016 11:22 am
by Thierry
Hi Ali,
Spending half an hour on this topic,
I came up with this one:
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function lineIsContinued pLine
return matchText( pLine, Rx )
end lineIsContinued
The datas I used for testing are valid LC statements which compile fine.
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on totest
put a \
into b
put a \ -- comment
into b
put a & ("xxx")\
into b
put b into c
put "a" &\
"b" into t
put a into t -- comment \ xxxx
put a into t -- comment \
get t
/* put "a" into */ put "a" into /* put "a" into */ \
t
put aaaa /* -- what about this one? */ into \
t
put b -- what about this one? */ into \
get the date
put ccc /* -- and this one? into \
t
*/
put " -- not a comment" \
into c
put " \ -- not a comment" into c
end totest
Applying a small test loop over these lines, here are my results:
( true means it's a continuedLine, false otherwise )
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true put a \
true put a \ -- comment
true put a & ("xxx")\
false put b into c
true put "a" &\
false put a into t -- comment \ xxxx
false put a into t -- comment \
true /* put "a" into */ put "a" into /* put "a" into */ \
true put aaaa /* -- what about this one? */ into \
false put b -- what about this one? */ into \
false put ccc /* -- and this one? into \
true put " -- not a comment" \
false put " \ -- not a comment" into c
Let me know if this suits you and if I missed any cases...
Kind regards,
Thierry
Re: Detecting if a script line has a line continuation chara
Posted: Thu Jul 14, 2016 12:09 pm
by [-hh]
Hi Thierry.
What's Rx?
Hermann
@Ali.
If comments are allowed after "\" then my function returns correctly true.
I thought it should return false then.