On Feb 23, 2011, at 6:37 PM, rjf wrote: > On Feb 23, 9:17 am, "Dr. David Kirkby" <david.kir...@onetel.net> > wrote: >> On 02/22/11 10:57 PM, Dr. David Kirkby wrote: >>> On 02/22/11 03:49 PM, rjf wrote: >>>> A parser for the maxima language is not only easier to write, >>>> it is available in source form. It is also based on a well known >>>> technique which is also used by Reduce. The real difficulty is >>>> to implement a Mathematica language parser, since the language >>>> fails to fit the standard expectations for computer languages. >> >>> I know you said that, but I've herd different from another source. See >> >>> http://groups.google.com/group/comp.compilers/msg/8c4e6ccad3c40599 >> >>> The person there, who is the CTO of a company producing this >> >>> http://www.semanticdesigns.com/Products/DMS/DMSToolkit.html >> >>> which has an option for a Mathematica parser (I assume the Mathematica >>> parser costs extra too). >> >>> He says Mathematica is not a particularly difficult language to parse, >>> and a GLR parser is a bit over the top. >> >> Here you can see a Mathematica parser is listed for the DMS toolkit >> >> http://www.semanticdesigns.com/Products/FrontEnds/index.html?Home=DMS... >> >> So I don't know what to believe Richard. You are saying the Mathematica >> language >> can't be parsed with a conventional parser, so had to hand-write the parser >> for >> MockMMA, yet someone from a commercial company selling this DMS toolkit >> claims >> the language is not particularly difficult to parse, and have a front end for >> their toolkit (a GLR parser) able to parse Mathematica. >> >> Clearly Wolfram|Alpha is a bit more clever, as it parsers written English and >> tries (sometimes not very successfully) to work with that. >> >> -- >> A: Because it messes up the order in which people normally read text. >> Q: Why is top-posting such a bad thing? >> A: Top-posting. >> Q: What is the most annoying thing in e-mail? >> >> Dave > > Here are my suggestions: > > 1. The guy is lying. He doesn't really have a Mathematica parser that > works. > 2. The company has a really neat parser generating tool and a lot of > engineering > to go with it and Mathematica can be easily parsed with it. > 3. The company has nothing much beyond a good term project in a > compiler-technology > course (perhaps at a graduate level) plus a bunch of engineering and > marketing. > > My guess is 1 + 3 > > A VERY simple example. > r[s[]] > > is legal in mathematica. > A traditional lexical analyzer, including the one apparently used by > mathematica, > typically looks for the longest string of characters that makes a > token. Hence > a===b has a token === which is "SameQ" even though there are > tokens = and ==. > So the longest one is found, in general. > > now in Mathematica, s[[4]] means take the 4th part of the list or > structure s. > s[4] means (essentially) call the function s on the argument 4. > { really it has > to do with pattern matching too, but that's a nuance not needed here.} > > anyway, how does one do lexical analysis or scanning on > r[s[]] ? > > The correct tokenization is r, [, s, [, ], ] . but the maximal > token deal returns > r, [, s, [, ]] . > > What does this mean? It means that the conventional separation of > lexical analysis > and parsing must be intermixed in parsing Mathematica. > > I know of no other programming language that requires this.
C++0x will require something similar for templates, so that std::vector<SomeType<bool>> x; will parse instead of requiring std::vector<SomeType<bool> > x; That said, I don't think many people consider C++ to be an easy language to parse. :-) -Ivan -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
