
Re: Mathematica and Lisp
Posted:
Jan 24, 2013 1:17 AM


On 1/22/2013 8:18 PM, David Bailey wrote: .... (regarding Lisp)
> Having 3 types of brackets, definitely helps to discern the structure, > even with indentation. Some lisp implementations allowed for the use of ] to terminate all open parentheses up to the prior [. It is possible to alter the meaning of characters in ANSI Common Lisp, so almost anything can be implemented.
Perhaps LISP could have been improved by > permitting all three, to be used interchangeably so long as they paired > correctly. I expect that this can be done, and maybe already exists. Mathematica does not allow the nesting of ([{}]) except for special uses, so building up a big expression as you type is probably about as error prone as Lisp, if not quite as unfamiliar. Note that f(a,g(b),c) has as many parens as the Lisp (f a (g b) c) and that using square brackets as f[a,g[b],c] is not much different. Also note that the highlighting of the matching left parenthesis is done in Mathematica's current front end. A similar feature is available in Lisp editors. > > Unless the infix front end distinguished reliably between code and data > (which I don't think it could, in general),
This is generally considered a benefit for advanced programming. On the other hand, most programmers spend their time composing programs for which it is pretty clear what is a program. Of the various types of data (array, vector, string, hash table, file descriptor, integer, float, complex, rational, ..., list ...) only one could possibly be a program, namely list. So it is perhaps not such a big problem as you might think.
you would still have a > problem  ideally you want to see > > sin(a) > > but > > (apples oranges pears) > > Also, if you print out an expression, you want the first format, and if > you print a list, you want the second.
Actually, the notation (sin a) instead of Sin[a] is pretty much of a wash. If you print a fragment of code, > you may want to see a mixture of both styles. Extra types of brackets > make all that simple. Or you may prefer uniformity. E.g. compare:
Mathematica Input, Mathematica FullForm Lisp
a+b+c Plus[a,b,c] (+ a b c) a^2 Power[a,2] (expt a 2) Sin[x] Sin[x] (sin x)
Also note that Mathematica has abandoned infix for such well known syntax as the "do" loop. This would ordinarily look like
for i=1 to 10 by 2 do f(i).... but is instead Do[f[i],{i,1,10,2}]. That's pretty close to (dotimes (f i) i 1 10 2). Incidentally, common lisp allows (loop for i from 1 to 10 step 2 do (f i)) or some such thing. [I don't use it much myself :)
>> > >> I rarely write programs of any length in Mathematica, because (as I've >> said) I hold the programming language in generally low regard. >> On the other hand I am pretty much familiar with the language because >> I wrote a parser for it (in Lisp) some time ago, and in my experience >> one of the best ways to really learn a language is to "implement" it. > > Did you implement it, or just parse it?
Certainly not all the application. Parser + pattern matcher + some simple application programs like differentiation, integration. numerical evaluation done differently; display. See my web page for free download. > > I do agree about learning a language by implementing it. Two of us once > wrote a Fortran compiler in Fortran (!!), and bootstrapped it. It was > widely used on Prime computers. One of the things I discovered, was that > the old issue about Fortran's context sensitive grammar, was an utterly > trivial problem!
I think there is a standard hack to recognize a "DO" statement by the fact that there is a comma not enclosed in parentheses. Check for this and handle the card differently. There are Fortran compilers written in Lisp; in fact most compiler implementations depend upon an intermediate expression tree language which requires that they include internally a subset of what some people would recognize as Lisp  for building and traversing trees. >> >> >> >> If I were using a computer to do something that required correct answers >> for, say, life safety, like building a bridge, I would follow WRI's >> advice and not use Mathematica. >> (see http://www.wolframalpha.com/termsofuse/) > > So have you found the perfect language  one in which none of the > functions contain imperfections, and yet which offers anything > approaching the computational sophistication of Mathematica?
I think that perfection depends on the context. Though they are not my areas of primary interest, I suspect the Mathematica is pretty good for some kinds of graphics (though I find it clumsy sometimes, that is probably my unfamiliarity with the nuances of Graphics objects), and maybe linear cellular automata. There seems to be a fairly strong consensus that for numerical programming there are other competitors favored in engineering schools.
> > BTW, I wouldn't be surprised if a lot of safety critical code isn't > written in Fortran!
I expect that is true. It would be a LOT easier to formally prove the correctness of a FORTRAN program than a Mathematica program. And there is even a history of proving FORTRAN compilers correct. I daresay no proof that Mathematica is correct is likely to appear any time soon.
RJF
> > David Bailey > http://www.dbaileyconsultancy.co.uk > > > >

