Thanks. The j formatting for ": was what I was missing. Using 0j2 gives me auto-width which makes life easier.
On Tue, Jan 7, 2014 at 5:44 PM, Raul Miller <rauldmil...@gmail.com> wrote: > J's rational and extended numbers are adequate for this task. You can > specify the dollars and cents directly and then use x: to convert them > rational. > > To get the desired display you'd probably want to use ": with a width > argument that specifies two digits after the decimal point. > > For example: > 20j2":,.(x:1 0.0765 1.0765)*(4000000000000000x*x:5.50)+2*x:2.86 > 22000000000000005.72 > 1683000000000000.44 > 23683000000000006.16 > > -- > Raul > > On Mon, Jan 6, 2014 at 9:16 PM, Ric Sherlock <tikk...@gmail.com> wrote: > > I had a go at producing a J submission for the RosettaCode Currency > > task<http://rosettacode.org/wiki/Currency>. It does the job, but I > > figure that doing exact calculations with currency > > is something that some forum members do routinely and wanted to get some > > ideas of better ways to approach it. > > > > This is the Task description: > > > > """ > > > > Show how you might represent currency in a simple example, using a data > > type that represent exact values of dollars and cents. Note for example > > that the IEEE 754 binary floating point representations of numbers like > > 2.86 and .0765 are not exact. > > > > For this example, data will be two items with prices in dollars and > cents, > > a quantity for each, and a tax rate. Use the values 4000000000000000 > > hamburgers at $5.50 each, 2 milkshakes at $2.86 each, and a tax rate of > > 7.65%. (That number of hamburgers is a 4 with 15 zeros after it. The > number > > is contrived to exclude naïve task solutions using 64 bit floating point > > types.) Compute and output the total price before tax, the tax, and the > > total with tax, and show results on this page. The tax value must be > > computed by rounding to the nearest whole cent and this exact value must > be > > added to the total price before tax. The output must show dollars and > cents > > with a decimal point. The three results displayed should be > > 22000000000000005.72, 1683000000000000.44, and 23683000000000006.16. > Dollar > > signs and thousands separators are optional. > > > > """ > > > > Below is my J solution - how to deal with "decimal type" routinely?: > > > > require 'format/printf' > > toCents=: _99 ". }:&.(_2&|.) {.~ 3 + '.' i.~ ] > > fromCents=: [: ,&'.'&.(_2&|.) ": > > hamburger_price=: toCents '5.50' > > milkshake_price=: toCents '2.86' > > tax_rate=: 0.0765 > > > > total_before_tax=: +/ 4000000000000000 2 *&x: hamburger_price , > milkshake_price > > tax=: tax_rate ([: <. 1r2&+)@*&x: total_before_tax > > total=: total_before_tax + tax > > > > (fromCents&.> total_before_tax,tax,total) printf~ noun define > > Total before tax: %22s > > Tax: %22s > > Total: %22s > > ) > > ---------------------------------------------------------------------- > > 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
