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- (define-module (rectangular)
- #:use-module (rnrs base)
- #:use-module ((guile) #:select (lambda* λ simple-format))
- #:use-module (tagged-data)
- #:use-module (math)
- #:export (make-from-real-imag
- make-from-mag-ang
- rectangular?
- data-tag
- real-part
- imag-part
- magnitude
- angle
- install-package))
- ;;; IMPROVEMENT: Instead of renaming all procedures to have a prefix
- ;;; or suffix or some other means of telling what implementation they
- ;;; are from, we put them in a separate module and distinguish them
- ;;; upon importing them. This way neither one of the
- ;;; implementors/coders need to care about name collisions.
- ;;; NOTE: A module system is not yet introduced yet in the book at the
- ;;; point of this exercise.
- ;; representation in rectangular form
- ;; z = x + iy, i^2 = -1 -> point in a plane, real: x, imaginary: y
- (define data-tag 'rectangular)
- ;;; Constructors.
- (define make-from-real-imag
- (λ (real imag)
- (attach-tag data-tag
- (cons real imag))))
- (define make-from-mag-ang
- (λ (mag ang)
- (attach-tag data-tag
- (cons (* mag (cos ang))
- (* mag (sin ang))))))
- ;;; Accessors.
- (define real-part
- (λ (num)
- (simple-format #t "real-part in rectangular num: ~a" num)
- (car num)))
- (define imag-part
- (λ (num)
- (cdr num)))
- (define magnitude
- (λ (num)
- (sqrt (+ (square (real-part num))
- (square (imag-part num))))))
- (define angle
- (λ (num)
- (atan (imag-part num)
- (real-part num))))
- (define rectangular?
- (λ (datum)
- (eq? (type-tag datum) data-tag)))
- (define install-package
- (λ (lookup-table put)
- (let iter
- ([funcs° (list make-from-real-imag
- make-from-mag-ang
- rectangular?
- data-tag
- real-part
- imag-part
- magnitude
- angle)])
- (cond
- [(null? funcs°) lookup-table]
- [else
- (put lookup-table op type func)
- (iter (cdr funcs°))]))))
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