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add three chapter 2 solutions & tests
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‎README.md

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@@ -7,7 +7,7 @@ My solutions to exercises of the CS textbook ['Structure and Interpretation of C
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* Each `src` file is self-contained, and deals with either one or multiple related exercises
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* Tests are included in the `test` directory
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Currently only Chapter 1 solutions and tests are uploaded (but I expect to add more). Any corrections or enhancements are welcome. Have fun!
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Currently only Chapter 1 and few Chapter 2 solutions and tests are uploaded (but I expect to add more). Any corrections or enhancements are welcome. Have fun!
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## License
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‎src/sicp_clojure/ch_2/ex_01_rational_numbers.clj

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; sicp-clojure - SICP exercise solutions in Clojure
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; Copyright (C) 2022 Ioannis Stefanis
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; This file is part of sicp-clojure.
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; sicp-clojure is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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; sicp-clojure is distributed in the hope that it will be useful, but
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; WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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; General Public License for more details.
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; You should have received a copy of the GNU General Public License
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; along with sicp-clojure. If not, see <https://www.gnu.org/licenses/>.
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(ns sicp_clojure.ch_2.ex_01_rational_numbers)
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;////// 2.1 //////
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;improve the function that defines rational numbers,
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;so that it can also normalize its sign
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;utils
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(defn gcd [a b]
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(if (= b 0)
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a
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(gcd b (mod a b))))
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;instead of: {list, car, cdr, cadr} of other Lisp dialects,
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;in Clojure we can use: {vector, first, next, second}
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;(a two-element vector does not resemble a cons pair,
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;but a list of two elements)
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(defn make-rat-version1 [n d]
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(vector n d))
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(defn make-rat-version2 [n d] ;normalizes sign
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(let [g (gcd n d)] ;(the existing implementation works fine)
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(vector (/ n g) (/ d g))))
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(defn make-rat-version3 [n d] ;normalizes sign
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((fn [g] (vector (/ n g) (/ d g))) ;function application
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(gcd n d)))
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(def make-rat make-rat-version2)
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(defn numer [x] (first x))
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(defn denom [x] (second x))
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(defn add-rat [x y]
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(make-rat (+ (* (numer x) (denom y)) (* (denom x) (numer y)))
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(* (denom x) (denom y))))
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(defn sub-rat [x y]
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(make-rat (- (* (numer x) (denom y)) (* (denom x) (numer y)))
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(* (denom x) (denom y))))
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(defn mul-rat [x y]
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(make-rat (* (numer x) (numer y))
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(* (denom x) (denom y))))
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(defn div-rat [x y]
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(make-rat (* (numer x) (denom y))
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(* (denom x) (numer x))))
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(defn equal-rat? [x y]
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(= (* (numer x) (denom y)) (* (denom x) (numer y))))
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(defn print-rat [x]
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(println (numer x) "/" (denom x)))
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;implementation
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(defn sign [x]
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(if (= x 0)
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0
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(/ x (Math/abs x))))
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(defn make-rat-version4 [n d] ;normalizes sign
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(let [g (gcd (Math/abs n) (Math/abs d))
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s (sign d)]
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(vector (/ n (* g s))
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(/ d (* g s)))))
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(defn make-rat-version5 [n d] ;normalizes sign
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(let [g (gcd (Math/abs n) (Math/abs d))
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s (sign d)]
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(vector (* (/ n g) s)
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(/ (Math/abs d) g))))

‎src/sicp_clojure/ch_2/ex_02_03_geometric_elements.clj

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; sicp-clojure - SICP exercise solutions in Clojure
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; Copyright (C) 2022 Ioannis Stefanis
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; This file is part of sicp-clojure.
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; sicp-clojure is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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; sicp-clojure is distributed in the hope that it will be useful, but
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; WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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; General Public License for more details.
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; You should have received a copy of the GNU General Public License
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; along with sicp-clojure. If not, see <https://www.gnu.org/licenses/>.
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(ns sicp_clojure.ch_2.ex_02_03_geometric_elements)
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;////// 2.2 & 2.3 //////
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;implement representations for points, line segments and plane rectangles
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;utils
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(defn average [x y] (/ (+ x y) 2))
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(defn square [x] (* x x))
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;implementation (2.2)
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(defn make-point [x y] (vector x y))
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(defn x-point [p] (first p))
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(defn y-point [p] (second p))
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(defn print-point [p] (println "(" (x-point p) "," (y-point p) ")"))
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(defn distance [p1 p2]
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(Math/sqrt (+ (square (- (x-point p1) (x-point p2)))
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(square (- (y-point p1) (y-point p2))))))
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(defn make-segment [p1 p2] (vector p1 p2))
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(defn start-segment [s] (first s))
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(defn end-segment [s] (second s))
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(defn midpoint-segment [s]
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(make-point (average (x-point (start-segment s)) (x-point (end-segment s)))
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(average (y-point (start-segment s)) (y-point (end-segment s)))))
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;implementation (2.3)
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;representation in terms of points (their order is important)
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(defn rectangle-version1 [p1 p2 p3 p4] (vector 1 p1 p2 p3 p4))
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(defn rect-version1-p1 [r] (first (next r)))
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(defn rect-version1-p2 [r] (first (next (next r))))
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(defn rect-version1-p3 [r] (first (next (next (next r)))))
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(defn rect-version1-p4 [r] (second (next (next (next r)))))
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;alternative representation in terms of segments (their order is important)
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(defn rectangle-version2 [s1 s2 s3 s4] (vector 2 s1 s2 s3 s4))
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(defn rect-version2-p1 [r] (start-segment (first (next r))))
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(defn rect-version2-p2 [r] (start-segment (first (next (next r)))))
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(defn rect-version2-p3 [r] (start-segment (first (next (next (next r))))))
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(defn rect-version2-p4 [r] (start-segment (second (next (next (next r))))))
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(defn representation [r] (first r))
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(defn rect-p1 [r]
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(cond (= (representation r) 1) (rect-version1-p1 r)
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(= (representation r) 2) (rect-version2-p1 r)))
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(defn rect-p2 [r]
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(cond (= (representation r) 1) (rect-version1-p2 r)
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(= (representation r) 2) (rect-version2-p2 r)))
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(defn rect-p3 [r]
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(cond (= (representation r) 1) (rect-version1-p3 r)
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(= (representation r) 2) (rect-version2-p3 r)))
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(defn rect-p4 [r]
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(cond (= (representation r) 1) (rect-version1-p4 r)
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(= (representation r) 2) (rect-version2-p4 r)))
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(defn rect-perimeter [r]
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(let [p1 (rect-p1 r)
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p2 (rect-p2 r)
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p3 (rect-p3 r)]
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(* 2 (+ (distance p1 p2) (distance p2 p3)))))
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(defn rect-area [r]
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(let [p1 (rect-p1 r)
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p2 (rect-p2 r)
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p3 (rect-p3 r)]
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(* (distance p1 p2) (distance p2 p3))))

‎test/sicp_clojure/ch_2/test_ex_01_rational_numbers.clj

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; sicp-clojure - SICP exercise solutions in Clojure
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; Copyright (C) 2022 Ioannis Stefanis
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; This file is part of sicp-clojure.
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; sicp-clojure is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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; sicp-clojure is distributed in the hope that it will be useful, but
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; WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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; General Public License for more details.
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; You should have received a copy of the GNU General Public License
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; along with sicp-clojure. If not, see <https://www.gnu.org/licenses/>.
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(ns sicp_clojure.ch_2.test_ex_01_rational_numbers
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(:require [clojure.test :refer [deftest is run-tests]]
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[sicp_clojure.ch_2.ex_01_rational_numbers
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:refer [add-rat make-rat-version1 make-rat-version2
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make-rat-version3 make-rat-version4 make-rat-version5
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print-rat equal-rat?]]))
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;////// 2.1 //////
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(def rat1 (make-rat-version1 -3 -5))
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(def rat2 (make-rat-version1 1 -5))
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(def rat3 (make-rat-version2 1 -5)) ;normalizes sign
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(def rat4 (add-rat rat1 rat2))
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(def rat5 (add-rat rat1 rat3))
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(run! print-rat [rat1 rat2 rat3 rat4 rat5])
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(newline)
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(def rat6 (make-rat-version3 -3 -5)) ;normalizes sign
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(def rat7 (make-rat-version4 1 -5)) ;normalizes sign
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(def rat8 (make-rat-version5 1 -5)) ;normalizes sign
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(def rat9 (add-rat rat6 rat7))
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(def rat10 (add-rat rat6 rat8))
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(run! print-rat [rat6 rat7 rat8 rat9 rat10])
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(deftest test1 (is (equal-rat? rat1 rat6)))
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(deftest test2 (is (equal-rat? rat2 rat7)))
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(deftest test3 (is (equal-rat? rat3 rat8)))
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(deftest test4 (is (equal-rat? rat4 rat9)))
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(deftest test5 (is (equal-rat? rat5 rat10)))
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(defn test-ns-hook [] ;to be run in order
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(test1) (test2) (test3) (test4) (test5))
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(run-tests)

‎test/sicp_clojure/ch_2/test_ex_02_03_geometric_elements.clj

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; sicp-clojure - SICP exercise solutions in Clojure
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; Copyright (C) 2022 Ioannis Stefanis
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; This file is part of sicp-clojure.
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; sicp-clojure is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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; sicp-clojure is distributed in the hope that it will be useful, but
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; WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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; General Public License for more details.
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; You should have received a copy of the GNU General Public License
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; along with sicp-clojure. If not, see <https://www.gnu.org/licenses/>.
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(ns sicp_clojure.ch_2.test_ex_02_03_geometric_elements
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(:require [clojure.test :refer [deftest is run-tests]]
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[sicp_clojure.ch_2.ex_02_03_geometric_elements
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:refer [make-point make-segment midpoint-segment x-point y-point
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rect-area rect-perimeter rectangle-version1 rectangle-version2]]))
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;////// 2.2 & 2.3 //////
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(defn print-equal? [x y]
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(println x y)
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(println (= x y))
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(= x y))
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(def point1 (make-point 0 0))
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(def point2 (make-point 0 4))
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(def point3 (make-point 5 4))
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(def point4 (make-point 5 0))
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(def seg1 (make-segment point1 point2))
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(def seg2 (make-segment point2 point3))
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(def seg3 (make-segment point3 point4))
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(def seg4 (make-segment point4 point1))
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(def midpoint1 (midpoint-segment seg1))
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(def rect1 (rectangle-version1 point1 point2 point3 point4))
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(def rect2 (rectangle-version2 seg1 seg2 seg3 seg4))
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(def per1 (rect-perimeter rect1))
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(def per2 (rect-perimeter rect2))
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(def area1 (rect-area rect1))
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(def area2 (rect-area rect2))
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;tests (2.2)
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(deftest test1 (is (print-equal? (x-point midpoint1) 0)))
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(deftest test2 (is (print-equal? (y-point midpoint1) 2)))
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;tests (2.3)
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(deftest test3 (is (print-equal? per1 per2)))
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(deftest test4 (is (print-equal? area1 area2)))
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(defn test-ns-hook [] ;to be run in order
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(test1) (test2) (test3) (test4))
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(run-tests)

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