Re: Lisp and J

Björn Helgason wrote:
> Frank Buss wrote:
> 
>
>
>
>   +/'5'=":i.100
> 20
>
>   sum=:+/
>
>   what=:'5'
>
>   equal=:=
>
>   format=:":
>
>   numbers=:i.100
>
>   sum what equal format numbers
> 20
>
This is supposed to tell me something?

First of all what in heavens name is =:?  Some languages use = for assignmen
t,
some use :=, but what is =:?

OK, I'll jump to the conclusion (based on the structure of your sequence of
whatever they are, lines, statements, assertions, declarations, expressions,
utterances, you come up with more possibilities)  that =: means "is defined 
to
be" similar to ::= in BNF.

sum=:+/  This is familiar from APL (presumably the APL content)

what=:'5'  sum what seems to say that the thing to be summed is 5

equal=:= equal is defined to be =, can't argue with that

format=:":  format is defined to be ": This explains a lot

numbers=:i.100 Ditto.  Hard to decide which of the last two lines is more
illuminating.

sum what equal format numbers
20

So you summed 4 5's  Where did the 4 come from?

Sorry for the somewhat sharp style of this post, but in my opinion a newsgro
up
posting should be designed to illuminate and instruct.  The linguae francae 
of
this news group are English for prose and APL for programming.  If you are g
oing
to explain to APL'ers what +/'5'=":i.100 means that might be useful, but do 
it
in English and/or APL or define your notation in those terms so that it is n
ot a
message only for insiders from some other world.

In article <%aC9e.40226$yV3.36249@clgrps12>,
"James J. Weinkam" <jjw@cs.sfu.ca> writes:
>...
>First of all what in heavens name is =:?  Some languages use = for assignme
nt,
>some use :=, but what is =:?
>...
>Sorry for the somewhat sharp style of this post, but in my opinion a newsgr
oup
>posting should be designed to illuminate and instruct....


I seldom post J to comp.lang.apl, but the above deserves some response.
Hope the following description is illuminating & instructive
(NB. comp.lang.lisp removed from groups).


J gives meaning to  C C. and C: for many ASCII characters C  e.g.
#   'number of items in' (e.g. number of items in a list)
A.  permutation: e.g.  4 A. 0 1 2  gives  2 0 1  (4th perm. of 0 1 2)
=:  means  'is_defined_to_be'
NB. commences an inline comment

NB.-------------------- start of J session --------------------
NB. original expression (spaced out for readability)
+/ '5' = ": i. 100
20
NB. give English names to some components of the above J sentence
numbers=: i. 100   NB. first 100 integers (starting from 0)
format=: ":        NB. ":  means format (i.e. give text representation)
equals=: =         NB. produces 1 for TRUE, 0 for FALSE
sum=: +/           NB. sum the items in a list
sum '5' equals format numbers   NB. i.e. how many 5s are there in 0-99?
20

NB. 2nd example:  mean  is_defined_to_be  sum_of  divided_by  number_of
mean=: +/ % #
mean %: i. 100     NB.  mean_of  square_roots_of  0,1...99
6.61463

NB. 3rd example:  note use of arbitrary-length integers (....x)
162115607033169106185260x A. 'tony blair maps our fate'
labour party manifesto
NB.--------------------- end of J session ---------------------

--
J.E.H.Shaw   [Ewart Shaw]      strgh@uk.ac.warwick    TEL: +44 2476 523069
Department of Statistics,  University of Warwick,  Coventry CV4 7AL,  UK
http://www.warwick.ac.uk/statsdept            http://www.ewartshaw.co.uk
3  ((4&({*.(=+/))++/=3:)@([:,/0&,^:(i.3)@|:"2^:2))&.>@]^:(i.@[)  <#:3 6 2

strgh@sherwood.csv.warwick.ac.uk wrote:
> In article <%aC9e.40226$yV3.36249@clgrps12>,
> 	"James J. Weinkam" <jjw@cs.sfu.ca> writes:
> 
>
>
>
> I seldom post J to comp.lang.apl, but the above deserves some response.
> Hope the following description is illuminating & instructive
> (NB. comp.lang.lisp removed from groups).
>

...

I wasn't so much asking for an expalnation of that particular fragment as as
king
that if J (or any other language other than APL) is posted here that it be
explained in such a way that APLers can understand it without having to obta
in
manuals and spend hours studying them.

Your post is a good example of how to do that.  I only hope that others who 
see
fit to post J examples here follow your lead.

In article <%aC9e.40226$yV3.36249@clgrps12>,
"James J. Weinkam" <jjw@cs.sfu.ca> writes:
>...
>First of all what in heavens name is =:?  Some languages use = for assignme
nt,
>some use :=, but what is =:?
>...
>Sorry for the somewhat sharp style of this post, but in my opinion a newsgr
oup
>posting should be designed to illuminate and instruct....


I seldom post J to comp.lang.apl, but the above deserves some response.
Hope the following description is illuminating & instructive
(NB. comp.lang.lisp removed from groups).


J gives meaning to  C C. and C: for many ASCII characters C  e.g.
#   'number of items in' (e.g. number of items in a list)
A.  permutation: e.g.  4 A. 0 1 2  gives  2 0 1  (4th perm. of 0 1 2)
=:  means  'is_defined_to_be'
NB. commences an inline comment

NB.-------------------- start of J session --------------------
NB. original expression (spaced out for readability)
+/ '5' = ": i. 100
20
NB. give English names to some components of the above J sentence
numbers=: i. 100   NB. first 100 integers (starting from 0)
format=: ":        NB. ":  means format (i.e. give text representation)
equals=: =         NB. produces 1 for TRUE, 0 for FALSE
sum=: +/           NB. sum the items in a list
sum '5' equals format numbers   NB. i.e. how many 5s are there in 0-99?
20

NB. 2nd example:  mean  is_defined_to_be  sum_of  divided_by  number_of
mean=: +/ % #
mean %: i. 100     NB.  mean_of  square_roots_of  0,1...99
6.61463

NB. 3rd example:  note use of arbitrary-length integers (....x)
162115607033169106185260x A. 'tony blair maps our fate'
labour party manifesto
NB.--------------------- end of J session ---------------------

--
J.E.H.Shaw   [Ewart Shaw]      strgh@uk.ac.warwick    TEL: +44 2476 523069
Department of Statistics,  University of Warwick,  Coventry CV4 7AL,  UK
http://www.warwick.ac.uk/statsdept            http://www.ewartshaw.co.uk
3  ((4&({*.(=+/))++/=3:)@([:,/0&,^:(i.3)@|:"2^:2))&.>@]^:(i.@[)  <#:3 6 2

strgh@sherwood.csv.warwick.ac.uk wrote:
> In article <%aC9e.40226$yV3.36249@clgrps12>,
> 	"James J. Weinkam" <jjw@cs.sfu.ca> writes:
> 
>
>
>
> I seldom post J to comp.lang.apl, but the above deserves some response.
> Hope the following description is illuminating & instructive
> (NB. comp.lang.lisp removed from groups).
>

...

I wasn't so much asking for an expalnation of that particular fragment as as
king
that if J (or any other language other than APL) is posted here that it be
explained in such a way that APLers can understand it without having to obta
in
manuals and spend hours studying them.

Your post is a good example of how to do that.  I only hope that others who 
see
fit to post J examples here follow your lead.