start of line parser
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Hi,
Jan has implemented a nice parser that allows us to specify easily productions that depend on text having to be on a new line. For example, in Pillar, a header is specified through an exclamation mark starting on a new line. Now, you can parse this as:
#startOfLine asParser , $! asParser , #newline asParser negate star Pretty cool! @Jan: I think we need to enhance a bit the implementation. The implementation looks like this right now:
isStartOfLine (position = 0) ifTrue: [ ^ true ]. ^ (collection at: position) = Character cr.
This will work when the line ending is either cr or lf+cr. However, it won't work if the line ending is just lf. For example, in my parsers, the newline implementation looks like:
(#cr asParser , #lf asParser optional) / #lf asParser / #cr asParser What do you think? Cheers, Doru "Every thing has its own flow"
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@Doru: This might solve the problem: isStartOfLine (position = 0) ifTrue: [ ^ true ]. ^ ((collection at: position) = Character cr) or: [ (collection at: position) = Character lf ]. Do you agree? Cheers, Jan On 3 September 2014 14:46, Tudor Girba <[hidden email]> wrote:
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I think this is not enough, because when you have cr+lf, you do not want to be true on cr. I think we should go with the the same rule as in the parser I proposed, which means that we need to reason about two characters. Doru On Wed, Sep 3, 2014 at 3:38 PM, Jan Kurš <[hidden email]> wrote:
"Every thing has its own flow"
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Ok, I ended up with this solution: The question that remains is, how to handle a situation when CR/LF/CRLF is at the end of the stream. Is it still a new line?isStartOfLine (position = 0) ifTrue: [ ^ true ]. self insideCRLF ifTrue: [ ^ false ]. ^ (self peekBack = Character cr) or: [ self peekBack = Character lf]. Jan
On 3 September 2014 15:52, Tudor Girba <[hidden email]> wrote:
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This looks good! I think that if we have a new line at the end of the stream, we should consider the last character a #startOfLine as well. This will have not much of an effect anyway, given that we will likely always use it in sequence with another parser.
Thanks, Doru On Wed, Sep 3, 2014 at 5:23 PM, Jan Kurš <[hidden email]> wrote:
"Every thing has its own flow"
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OK, lets keep it this way, if it will be problem in a future, I can add the extra check for the last line. Cheers, Jan On 4 September 2014 08:00, Tudor Girba <[hidden email]> wrote:
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