Boyko, congratulations! You manage to convince yourself that cm² is not an expression even if mc² is an expression. I don't follow. 3m*2m=6m². That is simple algebra where m*m=m² . Nor do I know what you mean by 'pushing their meaning too far.' - Bo
>________________________________ > Fra: Boyko Bantchev <boyk...@gmail.com> >Til: programm...@jsoftware.com >Sendt: 23:35 søndag den 9. december 2012 >Emne: Re: [Jprogramming] J v Python > >On 9 December 2012 23:17, Bo Jacoby <bojac...@yahoo.dk> wrote: >> Still it is an expression. Centi is one hundredth, 0.01, and 'meter' is an >> algebraic entity. Meter can be squared to give a unit of area, square meter, >> 'm²' . 'cm²' means square centimeter, (cm)². According to standard convention >> the square should be evaluated before the multiplication, so cm² should mean >> centi square meter, c(m²). > >That 'c' is for 'centi' does not make 'cm' or 'cm²' expressions – >you are explaining the etymology of 'cm' which I know anyway, but >'cm' is still a denotation and not a multiplication of anything. >Neither is 'cm²'. 'cm' is understood as a single symbol, and so >are 'm²', 'cm²', 'cm³' etc. These symbols are really (and >intentionally) reminiscent of expressions but are not ones. >Saying otherwise is, I think, pushing their meaning too far. > >> Q. 'How exactly is it better'? A. It is without the above exception, and it >> is easily generalized to >> more operations than addition, multiplication, and exponentiation. > >As I explained, there is no exception, since 'cm²' is not an >expression in the first place. By 'generalized' you seem to mean >that there are no precedence rules in J. But, as I pointed out, and >as we all perfectly know, this is only partially true. > >> Q. 'how does J convention lead to omitting parentheses'? A. The J convention >> allows a*(b+c) to be written a*b+c. The parentheses are omitted. > >They are not omitted in (a*b)+c, and, amusingly, in (c*m)^2. > >> Q. 'the precedences hardly present a problem'. A. Precedences present >> problems to the pupils even if it is no problem to you. > >Then the different precedences of verbs and adverbs/conjunctions, >especially along with the reverse order of application and binding of the >latter entities, should present more serious problems to pupils. >---------------------------------------------------------------------- >For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
