Detecting if a script line has a line continuation character

[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

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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

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(" something ") \

is

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") \

Moreover it will not work in the following case

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put "a" &\
"b" into tVar

The latter two examples would be fixed using

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char -1 of word -1 of pLine

, 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:

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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?

[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:

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/* put "a" into */ put "a" into /* put "a" into */ /
tVar

really has nothing to do with the line continuation char.

Craig Newman

[[-hh]]

My idea was wrong, sorry. It's too late in the evening.

[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

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put "a" &\

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

[[-hh]]

Hi Craig. Wasn't upset but had a wrong idea which fails if there are quoted comment chars in the line

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put "#//--" \
into b

[[-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:

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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.

[livecodeali]

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

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:

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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,

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put "\"

[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

[[-hh]]

Hi Thierry.

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return  matchText( pLine, Rx )

What's Rx?

Hermann

@Ali.
If comments are allowed after "\" then my function returns correctly true.

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put "\#//--\" \ --> returns true

I thought it should return false then.