2014-09-23 15:57 GMT+02:00 Udo Schneider <udo.schnei...@homeaddress.de>:
> > Confirmed in even a better way: given how convoluted and hacky is > > writing a full Python Parser, it is probably not even a Context Free > > Grammar. > Let's agree on the fact that you'll be able to parse it using Context > Sensitive Grammar (Type 1) for sure ... and if you're very lucky Context > Free (Type 2) might be sufficient but PITA to write and maintain. Agreed? > :-) > Agreed :) Thierry > > CU, > > Udo > > > > On 23.09.14 14:20, Thierry Goubier wrote: > >> >> >> 2014-09-23 13:57 GMT+02:00 Udo Schneider <udo.schnei...@homeaddress.de >> <mailto:udo.schnei...@homeaddress.de>>: >> >> >> > yeap noway I compare Regex with PettitParser. I will probably give a >> > PettitParser a try, because I try to parse Pharo syntax to Python, I >> > want now to parse Pharo classes to python class and that will be a >> > nightmare with regex, so time to give PettitParser a serious try. >> Without wanting to go too deep into theory... Parsing Pharo or >> Python would definitely need a Chromsky Type 2 language (Context >> free grammar). So you'd be out of luck parsing Smalltalk or Python >> code with Regular Expressions (Chromsky Type 3) only - except maybe >> for some very simple expressions. >> >> >> Confirmed in even a better way: given how convoluted and hacky is >> writing a full Python Parser, it is probably not even a Context Free >> Grammar. >> >> That is: the Python grammar is LALR which is a subset of Context Free >> Grammar (but already more than a type 3 Chomsky grammar), but the Lexer >> is a fair bit more than usual (dedent tokens come to mind; special >> handling of end of lines as well). >> >> I think you need a fair bit of special magic in PetitParser to parse >> Python. >> >> Luckily, Python is well documented in that regard. >> >> Thierry >> >> >> CU, >> >> Udo >> >> >> On 23.09.14 13:35, kilon alios wrote: >> >> yeap noway I compare Regex with PettitParser. I will probably >> give a >> PettitParser a try, because I try to parse Pharo syntax to >> Python, I >> want now to parse Pharo classes to python class and that will be a >> nightmare with regex, so time to give PettitParser a serious try. >> >> On Tue, Sep 23, 2014 at 1:10 PM, Udo Schneider >> <udo.schnei...@homeaddress.de >> <mailto:udo.schnei...@homeaddress.de> >> <mailto:udo.schneider@__homeaddress.de >> <mailto:udo.schnei...@homeaddress.de>>> >> wrote: >> >> > I have not used PettitParser yet, looks powerful but I >> find it a bit >> > weird in design. On the other hand regex is quite ugly >> and understanding >> > complex regex a pain. >> I normally encounter two issues with RegExps: >> >> 1) The syntax between different apps/libs/frameworks differs >> sligtly. Esp. for character classes or greediness. This >> drove me >> crazy more than one time. >> 2) Often enough I realize (while developing the RegExp) >> that I need >> something more capable than a Chomsky Type 3 parser (which >> RegExps >> are in a way). So I have to use "a bigger gun" - e.g. >> PetitParser. >> >> CU, >> >> Udo >> >> >> On 23.09.14 10:15, kilon alios wrote: >> >> it reminds a lot of Kent's Beck Smalltalk Practice >> Patterns where it >> removes all ifs and replaces them with regular unary >> messages . >> It is >> definitely an elegant way of coding making the code >> just flow. >> >> I have not used PettitParser yet, looks powerful but I >> find it a bit >> weird in design. On the other hand regex is quite ugly >> and >> understanding >> complex regex a pain. >> >> On Tue, Sep 23, 2014 at 11:07 AM, Udo Schneider >> <udo.schnei...@homeaddress.de >> <mailto:udo.schnei...@homeaddress.de> >> <mailto:udo.schneider@__homeaddress.de >> <mailto:udo.schnei...@homeaddress.de>> >> <mailto:udo.schneider@ >> <mailto:udo.schneider@>__homead__dress.de <http://homeaddress.de> >> <mailto:udo.schneider@__homeaddress.de >> <mailto:udo.schnei...@homeaddress.de>>>> >> wrote: >> >> > just as it is black magic for me now :D >> The nice thing about this approach is the fact >> that it "just" >> piggybacks the normal Smalltalk message sending. >> So you can >> step >> through it using the Debugger - it's Smalltalk all >> the way >> down. >> >> I still remember my first shock when (having no >> formal >> background on >> parsing theory at that time) I saw the parsing >> tables >> generated by >> T-Gen. Of course it was Smalltalk ... but >> understanding >> those tables >> was a nightmare. >> >> PetitParser is the gold standard here IMHO. It is >> able to parse >> arbitrary input (compared to my block expressions >> only). >> And you can >> still use the Debugger to step through the parsing >> process *and >> still understand what's going on!* >> >> CU, >> >> Udo >> >> On 23.09.14 09:54, kilon alios wrote: >> >> just as it is black magic for me now :D >> >> At least I get the general feeling. I am new >> to parsing >> too, so >> far I >> have only played with regex parsing. Not the >> most >> smalltalkish >> way but >> it works well so far. >> >> On Tue, Sep 23, 2014 at 9:39 AM, Udo Schneider >> >> <udo.schnei...@homeaddress.de >> <mailto:udo.schnei...@homeaddress.de> >> <mailto:udo.schneider@__homeaddress.de >> <mailto:udo.schnei...@homeaddress.de>> >> <mailto:udo.schneider@ >> <mailto:udo.schneider@>__homead__dress.de <http://homeaddress.de> >> <mailto:udo.schneider@__homeaddress.de >> <mailto:udo.schnei...@homeaddress.de>>> >> <mailto:udo.schneider@ <mailto:udo.schneider@> >> <mailto:udo.schneider@ >> <mailto:udo.schneider@>>__homea__d__dress.de >> <http://homead__dress.de> <http://homeaddress.de> >> >> >> >> <mailto:udo.schneider@ >> <mailto:udo.schneider@>__homead__dress.de <http://homeaddress.de> >> <mailto:udo.schneider@__homeaddress.de >> <mailto:udo.schnei...@homeaddress.de>>>>> >> wrote: >> >> Hi Estaban, >> >> I think the first time I saw this pattern >> was in >> ReStore on >> Dolphin >> Smalltalk. I didn't understand it's >> implementation >> back then. I >> assume that it's similar to what I >> described >> though. But >> having a >> Smalltalk block automagically creating the >> equivalent SQL >> SELECT >> expression was like black magic at that >> time :-) >> >> CU, >> >> Udo >> >> >> >> >> On 23.09.14 04:15, Esteban A. Maringolo >> wrote: >> >> Excellent article. >> >> I think GLORP uses a similar technique >> to >> setup its >> expressions, and >> also have issues with #and:/#or: >> selectors due to >> inlining, so >> it uses >> AND:/#OR: instead. >> >> Regards! >> >> Esteban A. Maringolo >> >> pd: Your blog and it's choosen topic >> made me >> remember >> http://use-the-index-luke.com/ >> >> 2014-09-22 20:48 GMT-03:00 Udo >> Schneider >> >> <udo.schnei...@homeaddress.de >> <mailto:udo.schnei...@homeaddress.de> >> <mailto:udo.schneider@__homeaddress.de >> <mailto:udo.schnei...@homeaddress.de>> >> <mailto:udo.schneider@ >> <mailto:udo.schneider@>__homead__dress.de <http://homeaddress.de> >> <mailto:udo.schneider@__homeaddress.de >> <mailto:udo.schnei...@homeaddress.de>>> >> <mailto:udo.schneider@ >> <mailto:udo.schneider@> >> <mailto:udo.schneider@ >> <mailto:udo.schneider@>>__homea__d__dress.de >> <http://homead__dress.de> <http://homeaddress.de> >> <mailto:udo.schneider@ >> <mailto:udo.schneider@>__homead__dress.de <http://homeaddress.de> >> <mailto:udo.schneider@__homeaddress.de >> <mailto:udo.schnei...@homeaddress.de>>>>>__: >> >> >> All, >> >> I just finished a blog entry. It >> shows how >> to use >> Smalltalk >> blocks as parsers/translators. E.g. >> translating a Block >> >> [:customer | (customer >> joinDate >> year is: Date >> today year)] >> >> into an SQL-like String >> >> >> (YEAR(customers.joinDate) = 2014) >> >> The SQL stuff is just an example >> - you can >> create >> nearly any >> output. >> >> Check out >> http://readthesourceluke.__blo______gspot.de/2014/09/block-_ >> _______translators-parsing-magic.__html >> <http://blo____gspot.de/2014/09/block-______translators- >> parsing-magic.html> >> >> <http://blo__gspot.de/2014/09/__block-____translators- >> parsing-__magic.html >> <http://blo__gspot.de/2014/09/block-____translators-parsing- >> magic.html>> >> >> >> <http://blogspot.de/2014/09/____block-__translators-parsing- >> ____magic.html >> <http://blogspot.de/2014/09/__block-__translators-parsing-__ >> magic.html> >> >> <http://blogspot.de/2014/09/__block-__translators-parsing-__ >> magic.html >> <http://blogspot.de/2014/09/block-__translators-parsing- >> magic.html>>> >> >> >> >> <http://readthesourceluke.__bl____ogspot.de/2014/09/block-__ >> ____translators-parsing-magic.html >> <http://bl__ogspot.de/2014/09/block-____translators-parsing- >> magic.html> >> >> <http://blogspot.de/2014/09/__block-__translators-parsing-__ >> magic.html >> <http://blogspot.de/2014/09/block-__translators-parsing- >> magic.html>> >> >> >> <http://readthesourceluke.__bl__ogspot.de/2014/09/block-____ >> translators-parsing-magic.html >> <http://blogspot.de/2014/09/block-__translators-parsing- >> magic.html> >> >> <http://readthesourceluke.__blogspot.de/2014/09/block-__ >> translators-parsing-magic.html >> <http://readthesourceluke.blogspot.de/2014/09/block- >> translators-parsing-magic.html>__>__>__> >> >> Maybe that's old stuff for some >> of you - >> but I hope >> it's >> interesting for some at least :-) >> >> Comments and feedback appreciated. >> >> CU, >> >> Udo >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> > > >
