I think we have covered these issues with you before. Do you remember why you should get that error?
Thanks, -- Raul On 7/8/14, Linda Alvord <[email protected]> wrote: > And then! > > h=: 3 :'0 x } y' > 4 5 h i.11 > |domain error: h > | 4 5 h i.11 > > Linda > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On BehalSSf Of Linda > Alvord > Sent: Tuesday, July 08, 2014 5:14 AM > To: [email protected] > Subject: Re: [Jprogramming] Tacit J and indexed replacement > > Ian's post was very early in this thread, but something has puzzled me for a > while as I tried to write a tacit version: > > f=: 13 :'0 x } y' > 4 5 f i.11 > 0 1 2 3 0 0 6 7 8 9 10 > g=: 4 :'0 x } y' > 4 5 g i.11 > 0 1 2 3 0 0 6 7 8 9 10 > > f > 4 : '0 x } y' > g > 4 : '0 x } y' > > 4!:0 <'f' > 3 > 4!:0 <'g' > 3 > > Linda > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Ian Clark > Sent: Sunday, July 06, 2014 3:54 AM > To: [email protected] > Subject: Re: [Jprogramming] Tacit J and indexed replacement > > I think Erling is quite right, if you take what he says literally: "Amend > is seldom useful for indexed replacement when you write tacit J". > > I'd go further and say "Amend is seldom useful." Period. I write a lot of J > code and I hardly ever use it. > > To someone coming from C (say), this cries out for explanation. In C, just > about everything is done by keyhole surgery, i.e. by tinkering with > whatever happens to be at the end of a pointer (read: index). In J, just > about nothing is done that way. > > Let me give an example. Suppose I want to write a verb to zero the x'th > element of a list y ... > I can easily write it as an explicit verb: > > zero=: 4 : '0 x} y' > 3 zero i.6 > 0 1 2 0 4 5 > > But "13 :" refuses to give me an equivalent tacit verb ... > > 13 : '0 x}y' > 4 : '0 x}y' > > Is this just a shortcoming of "13 :" ? Does anyone know a "nice" tacit > equivalent? I don't. > > Contrast this with what happens if I switch round 0 and x (...which gives > me a verb to replace the first element of a list y with x). In this case > "13 :" does deliver me a nice simple tacit equivalent ... > > 13 : 'x 0}y' > 0} > > So why doesn't 13 : '0 x}y' do something equally as nice? It's all > explained in http://www.jsoftware.com/jwiki/Vocabulary/curlyrt#dyadic . But > that doesn't really explain to a newcomer why Amend was designed as an > adverb: > x m} y > with (index) m as an *operand*, not an *argument*. > > Yes, I can write a tacit verb to zero the x'th element of list y ... > > zero2=: 13 : 'y * y~:x' > 3 zero2 i.6 > 0 1 2 0 4 5 > zero2 > ] * ~: > > ... but not by using Amend, which is quite simply not useful in that role. > Though I'm not claiming it can't be done - in fact there's a worked example > in: http://www.jsoftware.com/jwiki/Vocabulary/curlyrt#dyadic under "More > Information". But I wouldn't call it "nice". > > This illustrates the J approach to programming: > http://www.jsoftware.com/jwiki/Vocabulary/Loopless -and how it contrasts > with the C approach. Henry would explain it far better than I can, but he's > busy. > > IanClark > > > On Sat, Jul 5, 2014 at 8:59 PM, Erling Hellenäs <[email protected]> > wrote: > >> Hi all ! >> >> When you write tacit code, the index m used by Amend, syntax description >> x m} y, is a constant? >> Normally you have a variable you want to use for indexing? This means >> Amend is seldom useful for indexed replacement when you write tacit J? >> Are there any descriptions of nice ways to do indexed replacement in tacit >> J? >> As with Amend, the result has to be a new variable, of course. >> >> Cheers, >> >> Erling Hellenäs >> >> ---------------------------------------------------------------------- >> 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 > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
