BLOG: Block Translators - parsing magic
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BLOG: Block Translators - parsing magic
 
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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.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 |
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Udo Schneider wrote:
All, Very nice write up. Fairly straight forward to follow but not something I could have done from scratch. Nice to have a recipe for it. Thanks One spelling mistake... > This will give es enough clues This will give us enough clues cheers -ben |
Re: BLOG: Block Translators - parsing magic
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In reply to this post by Udo Schneider
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 <[hidden email]>: > > 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.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 > > |
Re: BLOG: Block Translators - parsing magic
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In reply to this post by Ben Coman
On 23.09.14 02:27, Ben Coman wrote: > Very nice write up. Fairly straight forward to follow but not something > I could have done from scratch. Nice to have a recipe for it. Thanks > > One spelling mistake... > > This will give es enough clues > This will give us enough clues Thanks for the feedback - the spelling mistake is fixed. Thanks, Udo |
Re: BLOG: Block Translators - parsing magic
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In reply to this post by Esteban A. Maringolo
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 <[hidden email]>: >> >> 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.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 >> >> > > |
Re: BLOG: Block Translators - parsing magic
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In reply to this post by Udo Schneider
Thanks Udo; I reviewed a few techniques for implementing internal / embeddel DSLs in a host language and I didn't saw this one :)2014-09-23 1:48 GMT+02:00 Udo Schneider <[hidden email]>: All, |
Re: BLOG: Block Translators - parsing magic
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In reply to this post by Udo Schneider
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 <[hidden email]> wrote: Hi Estaban, |
Re: BLOG: Block Translators - parsing magic
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> 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 > <[hidden email] > <mailto:[hidden email]>> 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 > <[hidden email] > <mailto:[hidden email]>>__: > > > 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.__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 > > > > > > > > |
Re: BLOG: Block Translators - parsing magic
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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 <[hidden email]> wrote: > just as it is black magic for me now :D |
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On Tue, Sep 23, 2014 at 1:45 PM, kilon alios <[hidden email]> wrote:
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Re: BLOG: Block Translators - parsing magic
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In reply to this post by Udo Schneider
Cool article & technique indeed. Ah Smalltalk, where were you all those years ;-) Speaking of PetitParser, which is excellent indeed, there is this #==> method in Boolean. PetitParser uses that a lot. I can use the thing but do not really grasps how it works. Now, the method comment says: Boolean #==> aBlock "The material conditional, also known as the material implication or truth functional conditional. Correspond to not ... or ... and does not correspond to the English if...then... construction. known as: b if a a implies b if a then b b is a consequence of a a therefore b (but note: 'it is raining therefore it is cloudy' is implication; 'it is autumn therefore the leaves are falling' is equivalence). Here is the truth table for material implication: p | q | p ==> q -------|-------|------------- T | T | T T | F | F F | T | T F | F | T " ^self not or: [aBlock value] This is still a bit foggy to me. Anyone caring to shed some light on that? What are the typical ways to use that? TIA Phil On Tue, Sep 23, 2014 at 10:07 AM, Udo Schneider <[hidden email]> wrote: > just as it is black magic for me now :D |
Re: BLOG: Block Translators - parsing magic
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In reply to this post by kilon.alios
On Tue, Sep 23, 2014 at 10:15 AM, kilon alios <[hidden email]> wrote:
Well, I started writing Regexes for parsing some flat file content. Quickly turned into a harder than needed way. Moved to PP and things are now crystal clear. Give it a shot, it is really powerful and easy to write once you get the hang of it. Phil
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Re: BLOG: Block Translators - parsing magic
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In reply to this post by kilon.alios
> 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 > <[hidden email] > <mailto:[hidden email]>> 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 > <[hidden email] > <mailto:[hidden email]> > <mailto:[hidden email] > <mailto:[hidden email]>>> > 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 > <[hidden email] > <mailto:[hidden email]> > <mailto:[hidden email] > <mailto:[hidden email]>>>__: > > > 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://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 > > > > > > > > > > > > |
Re: BLOG: Block Translators - parsing magic
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In reply to this post by philippeback
Phil,
I'd say that's an implementation of the "Material implication"[1] operator from Propositional calculus. You can write it as P -> Q and read it as "P implies Q" or (not 100% correct) "if P (is true) then Q (is true)". Let's take a look at the truth table: P | Q | P -> Q ---+---+------- t | t | t ---+---+------- inserting it into the statement above yields: "if true then true" which is true indeed. The funny thing starts when we look at the case(s), where P is false. The general (verbal) rule says that if the premise (P) is false the truth value of the conclusion doesn't matter. Hence the complete term is true: P | Q | P -> Q ---+---+------- f | t | t ---+---+------- f | f | t ---+---+------- There is one case left: What happens if the premise is true but the conclusion is false? That's in direct violation of the defintion which states that "if P (is true) then Q (is true)". As P is true and Q is false the truth value of the complete term is false! P | Q | P -> Q ---+---+------- t | f | f ---+---+------- Or to put it in different words: An implication can only be false if the premise is true but the conclusion is false. So we end up with this truth table: P | Q | P -> Q ---+---+------- t | t | t ---+---+------- f | t | t ---+---+------- f | f | t ---+---+------- t | f | f ---+---+------- We did not take a look yet, at how to implement this with basic boolean operators. So we need to take a look at the table and find the expression: Let's start with the exception (fourth case). We can express this as: !(P & !Q) -> "The term is false if P is true and Q is false" I added the inner term "P & !Q" to the table to make it easier to follow: P | Q | P -> Q | P & !Q | !(P & !Q) ---+---+--------+--------+----------- t | t | t | f | t ---+---+--------+--------+----------- f | t | t | t | f ---+---+--------+--------+----------- f | f | t | f | t ---+---+--------+--------+----------- t | f | f | f | t ---+---+--------+--------+----------- The "last" step is to simplify the term "!(P & !Q)" using one of de Morgan's laws: !(A & B) == !A | !B Using this for our term gives !(P & !Q) == !P | !!Q == !P | Q P | Q | P -> Q | P & !Q | !(P & !Q) | !P | Q ---+---+--------+--------+-----------+-------- t | t | t | f | t | t ---+---+--------+--------+-----------+-------- f | t | t | t | f | f ---+---+--------+--------+-----------+-------- f | f | t | f | t | t ---+---+--------+--------+-----------+-------- t | f | f | f | t | t ---+---+--------+--------+-----------+-------- So our final term is "correct" (proof in the truth table) and is equivalent to the smalltalk term: !P | Q := self not or: [aBlock value] I have to admit though that implications in Propositional calculus really gave me a headache. You might simply want to accept that they are defined this way. And maybe it doesn't help ... but there are even more strange things lurking around the corner [4] :-) Although not immidiatly obvious all the terms in Propositional calculus do not neccessarly have a semantic meaning in context to each other. They are totaly independent. The only thing that counts is the truth value of its terms. E.g. something like this is mathematically/syntacically valid but doesn't make any sense from a semantic point of view: P := I am 12y old Q := It rains The term "P -> Q" is perfectly fine mathematically/syntacically but doesn't mean anything in terms of semantics. Hope this helps. CU, Udo [1] http://en.wikipedia.org/wiki/Material_implication_(rule_of_inference) [2] http://en.wikipedia.org/wiki/Propositional_calculus [3] http://en.wikipedia.org/wiki/De_Morgan's_laws [4] http://en.wikipedia.org/wiki/Paradoxes_of_material_implication On 23.09.14 10:49, [hidden email] wrote: > Cool article & technique indeed. Ah Smalltalk, where were you all those > years ;-) > > Speaking of PetitParser, which is excellent indeed, there is this #==> > method in Boolean. > > PetitParser uses that a lot. I can use the thing but do not really > grasps how it works. > > Now, the method comment says: > > Boolean #==> aBlock > "The material conditional, also known as the material implication or > truth functional conditional.Correspond to not ... or ... and does not > correspond to the English if...then... construction. > known as: > b if a > a implies b > if a then b > b is a consequence of a > a therefore b (but note: 'it is raining therefore it is cloudy' is > implication; 'it is autumn therefore the leaves are falling' is > equivalence). > Here is the truth table for material implication: > p | q | p ==> q > -------|-------|------------- > T | T | T > T | F | F > F | T | T > F | F | T > " > > ^self not or: [aBlock value] > > > This is still a bit foggy to me. > > Anyone caring to shed some light on that? > What are the typical ways to use that? > > TIA > Phil > > > > > On Tue, Sep 23, 2014 at 10:07 AM, Udo Schneider > <[hidden email] > <mailto:[hidden email]>> 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 > <[hidden email] > <mailto:[hidden email]> > <mailto:[hidden email] > <mailto:[hidden email]>>> > 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 > <[hidden email] > <mailto:[hidden email]> > <mailto:[hidden email] > <mailto:[hidden email]>>>__: > > > 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://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 > > > > > > > > > > > > > |
Re: BLOG: Block Translators - parsing magic
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In reply to this post by Udo Schneider
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 <[hidden email]> wrote: > I have not used PettitParser yet, looks powerful but I find it a bit |
Re: BLOG: Block Translators - parsing magic
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2014-09-23 13:35 GMT+02:00 kilon alios <[hidden email]>:
Kilon, just remember that you have a full Smalltalk parser already in your image, called RBParser. For Python parsing, there is probably a PetitParser based parser somewhere and two implementations of a SmaCC-based Python parser (For Python 2.7.X). Thierry
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Re: BLOG: Block Translators - parsing magic
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In reply to this post by kilon.alios
> 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. 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 > <[hidden email] > <mailto:[hidden email]>> 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 > <[hidden email] > <mailto:[hidden email]> > <mailto:[hidden email] > <mailto:[hidden email]>>> > 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 > <[hidden email] > <mailto:[hidden email]> > <mailto:[hidden email] > <mailto:[hidden email]>> > <mailto:udo.schneider@ > <mailto:udo.schneider@>__homead__dress.de <http://homeaddress.de> > > <mailto:[hidden email] > <mailto:[hidden email]>>>> > 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 > <[hidden email] > <mailto:[hidden email]> > <mailto:[hidden email] > <mailto:[hidden email]>> > <mailto:udo.schneider@ > <mailto:udo.schneider@>__homead__dress.de <http://homeaddress.de> > <mailto:[hidden email] > <mailto:[hidden email]>>>>__: > > > 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://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 > > > > > > > > > > > > > > > > |
Re: BLOG: Block Translators - parsing magic
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In reply to this post by Udo Schneider
Thx for this! I'd say that the material is worthy of inclusion into a bool chapter. Phil Le 23 sept. 2014 12:51, "Udo Schneider" <[hidden email]> a écrit :
Phil, |
Re: BLOG: Block Translators - parsing magic
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In reply to this post by Udo Schneider
2014-09-23 13:57 GMT+02:00 Udo Schneider <[hidden email]>: > yeap noway I compare Regex with PettitParser. I will probably give a 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
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Re: BLOG: Block Translators - parsing magic
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damn you guys speak in a language I am not aware of :D Looks like I have reading to do. Anyway regex worked fin for converting pharo messages to python method calls and assignment / reading variables . Regex was actually quite simple to learn. Now for classes I dont know if RBParser would be an overkill or not, probably its good. I have asked before and I was shown how nodes works with AST but I have not used that information yet. I dont care about a full python parser, thats not my goal. Its not my goal to take pharo code and fully convert it to python code, only make it easy for pharoers to use python libraries. So I move in small steps , instead of trying to create a whole parser. Though a full python parser would not be a bad idea either. So I am definitely interested to what you saying. On Tue, Sep 23, 2014 at 3:20 PM, Thierry Goubier <[hidden email]> wrote:
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