Numbers are recognized by the word-former (aka lexical analyzer, tokenizer) and follow some well-defined rules that you can find in the Dictionary. 1jo. 1 or 1jo.1 is matched as number(s), as you can see by the results of
;: '1jo. 1' or ;: '1jo.1' but the numbers don't follow the rules, so they get error. Anything starting with a digit must be a number that follows the rules. 1j o. 1 is recognized as 3 words (as you can check), but 1j is not a valid number so you get an error there too. Henry Rich > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of dly > Sent: Thursday, June 29, 2006 9:16 PM > To: General forum > Subject: Re: [Jgeneral] significant digits > > Still playing with these but some help would help > > also why can you use > > 0j1p1 > 0j3.14159 > > but not > > o.1 > 3.14159 > 0jo.1 > |ill-formed number > > > > Donna > [EMAIL PROTECTED] > > > > On 30-Jun-06, at 1:05 AM, Henry Rich wrote: > > > More than one post in this thread has conflated 1r_1 with 1j_1 > > and I wonder if everyone who is interested (which doesn't > > include me) is getting the right meaning out of it. > > > > Henry Rich > > > >> > >> Eldon's point, and my code on arctan _1r1, were concerned with > >> variant > >> defintions of arctan. Arctan is normally defined by > restricting the > >> domain of tangent to the open interval (-1r2p1, 1r2p1), so it > >> always gives > >> an angle in the first or fourth quadrant. In many > >> applications, you want > >> the angle from the x-axis to the point (x,y), which can be in any > >> quadrant. This is basically arctan y%x, except it takes sign into > >> account. Library functions called atan2 usually do this, and > >> J does it > >> via angle (12&o.). Then arctan _1 is _1r4p1 (in the fourth > >> quadrant), > >> same as the angle to (1,_1), but different from the angle > to (_1,1). > >> > >> Best wishes, > >> > >> John > >> > >> > >> > --------------------------------------------------------------------- > >> - > >> 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
