On Apr 8, 2014, at 12:04 PM, John Clements <[email protected]> wrote:
> > On Apr 8, 2014, at 11:54 AM, Sam Tobin-Hochstadt <[email protected]> wrote: > >> On Tue, Apr 8, 2014 at 2:48 PM, John Clements <[email protected]> >> wrote: >>> Here’s a short piece of code that tries to plot an array: >>> >>> #lang typed/racket >>> >>> (require plot >>> math/array) >>> >>> (define fft-maxes (array #[3.2 978.9 -2397])) >>> >>> (: with-indexes (Vectorof (Vector Nonnegative-Integer Real))) >>> (define with-indexes >>> (for/vector : (Vectorof (Vector Nonnegative-Integer Real)) >>> ([i : Nonnegative-Integer (in-naturals)] >>> [a (in-array fft-maxes)]) >>> (ann (vector (ann i Nonnegative-Integer) a) >>> (Vector Nonnegative-Integer Real)))) >>> >>> >>> (plot (lines (in-vector with-indexes))) >>> >>> I have two questions. >>> 1) Is there an easier way to pair an array with indices? This was kind of >>> challenging. >> >> Try `in-indexed`. > > But… in-indexed produces a sequence of 2-value elements. I guess I can get it > working with sequence-map: > > (plot (lines (sequence-map (lambda (a b) (vector b a)) > (in-indexed (in-array fft-maxes))))) > > BUT WAIT! no, that doesn’t work in the typed setting, because sequence-map’s > type doesn’t work for 2-valued sequences. Back to square 1. Got it… “in-values-sequence”. John > >> >>> 2) When I run this, I get >>> >>> Type Checker: missing type for identifier; >>> consider using `require/typed' to import it >>> identifier: idX9 >>> from module: plot in: #%module-begin >>> . Type Checker: missing type for identifier; >>> consider using `require/typed' to import it >>> identifier: idX54 >>> from module: plot/no-gui in: #%module-begin >>> . Type Checker: Summary: 2 errors encountered in: >>> #%module-begin >>> #%module-begin >> >> These are both from the use of `in-array` and/or `fft-maxes`, not from >> your for loop. Probably the right thing is to use `plot/typed`. > > Ah! I tried typed/plot, but not plot/typed. > > Many thanks. > > John > ____________________ Racket Users list: http://lists.racket-lang.org/users
