146 lines
5.7 KiB
Racket
146 lines
5.7 KiB
Racket
#lang racket/base
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;; Functions that sample from functions, and functions that create memoized samplers.
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(require racket/match racket/flonum racket/math racket/contract racket/list
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"contract-doc.rkt"
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"math.rkt"
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"axis-transform.rkt")
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(provide (all-defined-out))
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(define (build-linear-seq start step num)
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(for/list ([n (in-range num)])
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(+ start (* n step))))
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(defproc (linear-seq [start real?] [end real?] [num exact-nonnegative-integer?]
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[#:start? start? boolean? #t]
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[#:end? end? boolean? #t]) (listof real?)
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(cond
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[(zero? num) empty]
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; ambiguous request: arbitrarily return start
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[(and start? end? (= 1 num)) (list start)]
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[else
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(define size (- end start))
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(define step (/ size (cond [(and start? end?) (- num 1)]
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[(or start? end?) (- num 1/2)]
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[else num])))
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(define real-start
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(cond [start? start]
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[else (+ start (* 1/2 step))]))
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(build-linear-seq real-start step num)]))
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(defproc (linear-seq* [points (listof real?)] [num exact-nonnegative-integer?]
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[#:start? start? boolean? #t]
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[#:end? end? boolean? #t]) (listof real?)
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(let/ec return
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(when (empty? points) (raise-type-error 'linear-seq* "nonempty (listof real?)" points))
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(define pts (list->vector points))
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(define len (vector-length pts))
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(define indexes (linear-seq 0 (sub1 len) num #:start? start? #:end? end?))
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(define int-parts (map floor indexes))
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(define frac-parts (map - indexes int-parts))
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(map (λ (i f)
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(if (= i (sub1 len))
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(vector-ref pts i)
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(blend (vector-ref pts (add1 i)) (vector-ref pts i) f)))
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int-parts frac-parts)))
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(struct mapped-function (f fmap) #:transparent
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#:property prop:procedure
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(λ (g x) ((mapped-function-f g) x)))
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(define (map* f xs)
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(match f
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#;; gives obviously wrong chaperone error (tries to apply a hash?):
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[(mapped-function _ fmap) (fmap xs)]
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[(? mapped-function?) ((mapped-function-fmap f) xs)]
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[_ (map f xs)]))
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(defproc (nonlinear-seq [start real?] [end real?] [num exact-nonnegative-integer?]
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[transform axis-transform/c]
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[#:start? start? boolean? #t]
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[#:end? end? boolean? #t]) (listof real?)
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(match-define (invertible-function _ finv) (apply-transform transform start end))
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(map finv (linear-seq start end num #:start? start? #:end? end?)))
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(define 2pi (* 2 pi))
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(define ((2d-polar->3d-function f) x y z)
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(let ([x (exact->inexact x)]
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[y (exact->inexact y)]
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[z (exact->inexact z)])
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(define-values (θ ρ)
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(cond [(and (fl= x 0.0) (fl= y 0.0)) (values 0.0 0.0)]
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[else (values (flmodulo (flatan2 y x) 2pi)
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(flatan (fl/ z (distance x y))))]))
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(define r (exact->inexact (f θ ρ)))
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(fl- r (distance x y z))))
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(define (sample-parametric f t-min t-max samples)
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(map* f (linear-seq t-min t-max samples)))
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(define (sample-polar f θ-min θ-max samples)
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(define θs (linear-seq θ-min θ-max samples))
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(define rs (map* f θs))
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(map polar->cartesian θs rs))
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(define (sample-2d-polar f θ-min θ-max θ-samples ρ-min ρ-max ρ-samples)
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(for*/list ([θ (in-list (linear-seq θ-min θ-max θ-samples))]
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[ρ (in-list (linear-seq ρ-min ρ-max ρ-samples))])
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(3d-polar->3d-cartesian θ ρ (f θ ρ))))
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(define ((make-function->sampler transform-thnk) f)
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(define memo (make-hash))
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(λ (x-min x-max x-samples)
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(define tx (transform-thnk))
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(hash-ref! memo (vector x-min x-max x-samples tx)
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(λ ()
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(define xs (nonlinear-seq x-min x-max x-samples tx))
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(list xs (map* f xs))))))
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(define ((make-2d-function->sampler transform-x-thnk transform-y-thnk) f)
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(define memo (make-hash))
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(λ (x-min x-max x-samples y-min y-max y-samples)
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(define tx (transform-x-thnk))
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(define ty (transform-y-thnk))
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(hash-ref! memo (vector x-min x-max x-samples tx y-min y-max y-samples ty)
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(λ ()
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(define xs (nonlinear-seq x-min x-max x-samples tx))
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(define ys (nonlinear-seq y-min y-max y-samples ty))
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(list xs ys (for/vector #:length y-samples ([y (in-list ys)])
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(for/vector #:length x-samples ([x (in-list xs)])
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(f x y))))))))
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(define ((make-3d-function->sampler transform-x-thnk transform-y-thnk transform-z-thnk) f)
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(define memo (make-hash))
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(λ (x-min x-max x-samples y-min y-max y-samples z-min z-max z-samples)
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(define tx (transform-x-thnk))
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(define ty (transform-y-thnk))
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(define tz (transform-z-thnk))
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(hash-ref! memo (vector x-min x-max x-samples tx
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y-min y-max y-samples ty
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z-min z-max z-samples tz)
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(λ ()
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(define xs (nonlinear-seq x-min x-max x-samples tx))
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(define ys (nonlinear-seq y-min y-max y-samples ty))
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(define zs (nonlinear-seq z-min z-max z-samples tz))
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(list xs ys zs (for/vector #:length z-samples ([z (in-list zs)])
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(for/vector #:length y-samples ([y (in-list ys)])
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(for/vector #:length x-samples ([x (in-list xs)])
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(f x y z)))))))))
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(define (2d-sample->list zss)
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(for*/list ([zs (in-vector zss)]
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[z (in-vector zs)])
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z))
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(define (3d-sample->list dsss)
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(for*/list ([dss (in-vector dsss)]
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[ds (in-vector dss)]
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[d (in-vector ds)])
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d))
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