The x: mechanism does first convert to floats, and then to rationals. As long as your values are not too large, the result should be exact.
I imagine that it would be nice if dyadic ". or a workalike could support direct interpretation as rational numbers. FYI, -- Raul On Wed, Jan 6, 2021 at 4:48 AM Justin Paston-Cooper <paston.coo...@gmail.com> wrote: > > Thanks. Seems to be working now, even with a parenthesis removed from > each end. I wasn't getting a syntax error. Weird. > > I don't see what you mean by "doesn't give the number you suggest". I > think I am missing something. 33333/50 is equal to 666.66. 333/50 is > equal to 6.66. This is what I expected. > > As far as I understand, your solution parses strings to floats, and > then converts to extended. Don says that the internal float > representation is not an exact representation of the string. This > would make sense. It may be the case that your examples correspond > with the input numbers. I would imagine that for larger numbers there > would be a discrepancy. > > ([: x: 0&".) '10000000000.12345' gives: > > 810000000010r81 > > This is close, but not equal to the input. > > stringToRational '10000000000.12345' gives: > > 200000000002469r20000 > > This is correct. > > My solution parses the digits exactly as if there were no dot and > divides by 10^(number of digits after point). > > On Wed, 6 Jan 2021 at 12:20, Ric Sherlock <tikk...@gmail.com> wrote: > > > > Hi Justin, > > I'm not entirely clear what your desired behaviour/use case is, however if > > you add another closing parenthesis then your definition above does not > > give a (syntax) error, but doesn't give the number you suggest. > > > > stringToRational =: ((_&".)@(-.&'.') %&:x: 10&^@(<:@# - (i.&'.'))) > > > > stringToRational '666.66' > > > > 33333r50 > > > > stringToRational '6.66' > > > > 333r50 > > > > > > Assuming you just want to represent all strings as their equivalent > > rationals, is there a reason not to define stringToRational like this? > > > > stringToRational =: [: x: 0&". > > > > stringToRational '666.66' > > > > 33333r50 > > > > stringToRational&> '66666';'6666.6';'666.66';'66.666';'6.6666';'0.66666' > > > > 66666 33333r5 33333r50 33333r500 33333r5000 33333r50000 > > > > > > > > On Wed, Jan 6, 2021 at 8:20 PM Justin Paston-Cooper > > <paston.coo...@gmail.com> > > wrote: > > > > > Thanks for the suggestion. I've combined Don's idea of using x: and > > > your idea of removing the point and parsing that to handle all numbers > > > of digits after the decimal point: > > > > > > stringToRational =: ((_&".)@(-.&'.') %&:x: 10&^@(<:@# - (i.&'.')) > > > > > > stringToRational '666.66' should give 333r50. > > > > > > Sadly this is giving a domain error, even though both sides of the > > > fork work alone. Could anyone suggest how to fix this? > > > > > > On Tue, 5 Jan 2021 at 19:14, Jimmy Gauvin <jimmy.gau...@gmail.com> wrote: > > > > > > > > IF your strings always have two numbers after the decimal point you > > > > could > > > > remove the point before converting to numeric. > > > > > > > > NB.Remove decimal point > > > > '.' -.~ each '123.45' ; '1456.12' > > > > ┌─────┬──────┐ > > > > │12345│145612│ > > > > └─────┴──────┘ > > > > > > > > NB. Convert to numeric > > > > _ ". > '.' -.~ each '123.45' ; '456.12' > > > > 12345 45612 > > > > > > > > NB. type 4 is integer > > > > 3!:0 ] _ ". > '.' -.~ each '123.45' ; '456.12' > > > > 4 > > > > > > > > On Tue, Jan 5, 2021 at 10:43 AM Justin Paston-Cooper < > > > > paston.coo...@gmail.com> wrote: > > > > > > > > > Hello, > > > > > > > > > > I am reading in tab-separated files with readdsv from 'tables/dsv'. > > > > > Some columns consist of exact decimal numbers like 6.66. These > > > generally > > > > > involve amounts of a decimal currency. These are read in by readdsv as > > > > > boxed strings. makenum from 'tables/csv' converts these strings to > > > > > floats. I would like these strings to be converted exactly to > > > > > rationals. How can I go about this in the easiest and most efficient > > > > > way? I could not find information on parsing data types from strings. > > > > > > > > > > Thanks in advance, > > > > > > > > > > Justin > > > > > ---------------------------------------------------------------------- > > > > > 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 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
