Actually, it looks like the dyadic "do" avoids many common problems like
this:
_99 ". '24 14.9 41.9 25.1 -62 16.8 0.2 .2 -68.8 54 75.8 BadVal 1e+3
1+e+3'
where _99 replaces parts that couldn't be converted to valid numbers.
On 4/15/07, Devon McCormick <[EMAIL PROTECTED]> wrote:
Negative numbers would be a common stumbling block since J uses "_" to
represent
negatives, e.g.
". '24 14.9 41.9 25.1 -62 16.8 86.2 -68.8 54 75.8'
|length error
| 24 14.9 41.9 25.1 -62 16.8 86.2-68.8 54 75.8
because the "-" is interpreted as the dyadic function "minus". So, you'd
have to replace
all "-"s with "_"s before applying "do":
(3 : '(''-''=y)}y,:''_''')'24 14.9 41.9 25.1 -62 16.8 86.2 -68.8 54
75.8' NB. Replacement...
24 14.9 41.9 25.1 _62 16.8 86.2 _68.8 54 75.8
".(3 : '(''-''=y)}y,:''_''')'24 14.9 41.9 25.1 -62 16.8 86.2 -68.8 54
75.8'
24 14.9 41.9 25.1 _62 16.8 86.2 _68.8 54 75.8
On 4/15/07, Henry Rich < [EMAIL PROTECTED]> wrote:
>
> fastest way to turn the string s to its value is
>
> ". s
>
> You may get an error if it's ill-formatted.
>
> Henry Rich
>
> > -----Original Message-----
> > From: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED] On Behalf Of Amelia Stein
> > Sent: Sunday, April 15, 2007 1:44 PM
> > To: Programming forum
> > Subject: Re: [Jprogramming] J script files
> >
> > So how do you actually "scan" in a number from standard
> > input? What is the
> > syntax? Whether or not it is of good form in J, I have a
> > presentation to do
> > tomorrow where I need input from the keyboard.
> >
> > On 4/15/07, Devon McCormick <[EMAIL PROTECTED]> wrote:
> > >
> > > Randy -
> > >
> > > I think it's a mis-characterization to say that J "isn't
> > meant for user
> > > input".
> > > In fact, due to its interpretive nature, J handles user
> > input beautifully
> > > compared
> > > to any conventional language, if you use the language
> > itself. Of course,
> > > as
> > > an avid APLer, I'm sure this isn't news to you.
> > >
> > > But this prompt-based notion won't die, no matter how crippled it is
>
> > > compared
> > > to simply using native J. Take, for instance, the outline
> > of the program
> > > that
> > > Amelia is writing: allow someone to enter some numbers,
> > then return some
> > > descriptive statistics about them. Using J, I would naturally do
> > > something
> > > like
> > >
> > > (<./,>./,mean,stddev) 97.1 4.7 33 1.3 22 60 27.6 96.4 87.1 67.5
> > > 1.3 97.1 49.67 36.744585
> > >
> > > However, as Amelia's professor has constrained the problem,
> > the "correct"
> > > session might look more like this:
> > >
> > > Enter some numbers: 97.1 4.7 33 1.3 22 60 27.6 96.4 87.1 67.5
> > > ** Error: can only accept 5 numbers.
> > > Enter some numbers: 97.1 4.7 33 1.3 22
> > > The minimum is 1.3.
> > > The maximum is 97.1.
> > > The mean is 31.62.
> > > The standard deviation is 38.813876.
> > >
> > > or some such limited, simplistic implementation. Notice
> > how thoroughly
> > > inadequate this prompt-based paradigm is for getting any
> > serious work
> > > done:
> > > it's probably constrained to some fixed number of entries
> > or necessitates
> > > added complexity to acommodate a variable number of
> > entries. Furthermore,
> > > an input mistake can only be corrected by re-typing the
> > entire set of
> > > entries
> > > and the result can only be used by manually transferring it.
> > >
> > > (Of course, using a spreadsheet may also be a good way to
> > handle a problem
> > > like this.)
> > >
> > > This prompt+manual input notion is a lousy paradigm that is
> > encumbered by
> > > widely-accepted, unnecessary limitations of the past 50
> > years. Today, we
> > > have
> > > scalpels and laser beams but most people still insist on
> > using sticks and
> > > rocks.
> > >
> > > However true all this all is, the problem of user input
> > seems to be a
> > > recurring one in J.
> > > Those of us who use the language a lot have solved it for
> > ourselves but it
> > > recurs
> > > regularly for beginners. We've talked about this a bit in
> > the NYCJUG and
> > > the
> > > consensus seems to be 1) use file-based input, or 2) use a
> > spreadsheet
> > > front-end.
> > >
> > > One other idea is to use the GUI-building capabilities of some other
>
> > > language,
> > > like Java or VB, and
> > > interface the resulting GUI with J. Until get something like
> > > this fully fleshed out on the Wiki, we may have to make do
> > by referring
> > > people to
> > > the character-based solutions for Amelie that came out of
> > this thread.
> > >
> > > Devon
> > >
> > > On 4/15/07, ramacd < [EMAIL PROTECTED]> wrote:
> > > >
> > > >
> > > >
> > > > Dan Bron wrote:
> > > > > This is easy to see if we take a reductionist approach:
> > a single J
> > > > > token is either a built-in J primitive, or it's a
> > user-defined name
> > > > > with an arbitrary definition. Primitives never change
> > their definition
> > > > > (good thing!). And the dictionary of J explicitly states, at
> > > > > http://www.jsoftware.com/help/dictionary/dict2.htm that:
> > > > Primitives don't change their definition over a single
> > version of J,
> > > > that is true. Over multiple versions it is a different
> > story. In fact,
> > > > I long ago coined a term ("getting henked") for the suffering one
> > > > undergoes when one assumes upward compatibility.
> > > >
> > > > On the original idea of this thread, having a REPL facility, which
> > > > doesn't come in primitive-only J, doesn't strike me as a
> > stretch of its
> > > > capabilities. I do wonder at the (if you want a
> > responsive computer,
> > > > don't let a user near J) attitude, and where it comes
> > from. Amelia's
> > > > note that J "isn't meant for user input." crystallizes a
> > big misgiving I
> > > > have about J, even though I have been pro-J since J has
> > been around.
> > > >
> > > > >: ...
> > > >
> > > >
> > ----------------------------------------------------------------------
>
> > > > For information about J forums see
> > http://www.jsoftware.com/forums.htm
> > > >
> > >
> > >
> > >
> > > --
> > > Devon McCormick, CFA
> > > ^me^ at acm.
> > > org is my
> > > preferred e-mail
> > >
> > ----------------------------------------------------------------------
> > > For information about J forums see
> > http://www.jsoftware.com/forums.htm
> > >
> > ----------------------------------------------------------------------
> > For information about J forums see
> > http://www.jsoftware.com/forums.htm
>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
--
Devon McCormick, CFA
^me^ at acm.
org is my
preferred e-mail
--
Devon McCormick, CFA
^me^ at acm.
org is my
preferred e-mail
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
