9 files changed, 349 insertions, 0 deletions
diff --git a/net/ricketyspace/sicp/one/eight.scm b/net/ricketyspace/sicp/one/eight.scm
new file mode 100644
index 0000000..8157c23
--- /dev/null
+++ b/net/ricketyspace/sicp/one/eight.scm
@@ -0,0 +1,38 @@
+;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;; International. See
+;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+(define-module (net ricketyspace sicp one eight)
+  #:export (cube double
+            div-three improve
+            good-enough? cbrt-iter
+            cbrt-sicp))
+
+(use-modules (one six))
+
+(define (cube x)
+  (* (square x) x))
+
+(define (double x)
+  (* 2 x))
+
+(define (div-three x)
+  (/ x 3.0))
+
+(define (improve y x)
+  (div-three (+ (/ x (square y))
+                (double y))))
+
+(define (good-enough? y x)
+  (< (abs (- (cube y) x))
+     0.001))
+
+(define (cbrt-iter y x)
+  (if (good-enough? y x)
+      y
+      (cbrt-iter (improve y x)
+                 x)))
+
+(define (cbrt-sicp x)
+  (cbrt-iter 1.0 x))
+
diff --git a/net/ricketyspace/sicp/one/eleven.scm b/net/ricketyspace/sicp/one/eleven.scm
new file mode 100644
index 0000000..baa129b
--- /dev/null
+++ b/net/ricketyspace/sicp/one/eleven.scm
@@ -0,0 +1,41 @@
+;;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;;; International. See
+;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+(define-module (net ricketyspace sicp one eleven)
+  #:export (recursive-fn
+            make-cache
+            alt-recursive-fn))
+
+(define (recursive-fn n)
+  (cond ((<= n 3) n)
+        (else (+ (* 1 (recursive-fn (- n 1)))
+                 (* 2 (recursive-fn (- n 2)))
+                 (* 3 (recursive-fn (- n 3)))))))
+
+;;;; alternative version. faster but ugly.
+
+(define (make-cache)
+  (let ((cache (make-hash-table)))
+    (define (get key)
+      (hash-get-handle cache key))
+    (define (set key value)
+      (hash-create-handle! cache key value)
+      ;; return value as a side effect.
+      value)
+    (lambda args
+      (apply (case (car args)
+               ((get) get)
+               ((set) set)
+               (else (error "Invalid method")))
+             (cdr args)))))
+
+(define (alt-recursive-fn cache n)
+  (let ((v (cache 'get n)))
+    (cond (v (cdr v))
+          ((<= n 3)
+           (cache 'set n n))
+          (else (cache 'set n
+                       (+ (* 1 (alt-recursive-fn cache (- n 1)))
+                          (* 2 (alt-recursive-fn cache (- n 2)))
+                          (* 3 (alt-recursive-fn cache (- n 3)))))))))
diff --git a/net/ricketyspace/sicp/one/fifteen.scm b/net/ricketyspace/sicp/one/fifteen.scm
new file mode 100644
index 0000000..a61fa8f
--- /dev/null
+++ b/net/ricketyspace/sicp/one/fifteen.scm
@@ -0,0 +1,31 @@
+;;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;;; International. See
+;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+(define-module (net ricketyspace sicp one fifteen)
+  #:use-module (ice-9 regex)
+  #:export (sine))
+
+(define (sine angle)
+  (let ((out ""))
+    (define (log angle)
+      (set! out (string-append out " (p (sine "
+                               (number->string (/ angle 3.0)))))
+    (define (close-parens s)
+      (string-trim (string-append
+                    s (fold-matches "\\([p,s]" s ""
+                                    (lambda (match prev)
+                                      (string-append prev ")"))))))
+    (define (cube x) (* x x x))
+    (define (p x) (- (* 3 x) (* 4 (cube x))))
+    (define (s angle)
+      (if (not (> (abs angle) 0.1))
+          angle
+          (begin
+            (log angle)
+            (p (s (/ angle 3.0))))))
+    (s angle)
+    (close-parens out)))
+;;
+;; (sine 12.15)
+;; $25 = "(p (sine 4.05 (p (sine 1.3499999999999999 (p (sine 0.44999999999999996 (p (sine 0.15 (p (sine 0.049999999999999996))))))))))"
diff --git a/net/ricketyspace/sicp/one/five.scm b/net/ricketyspace/sicp/one/five.scm
new file mode 100644
index 0000000..f387919
--- /dev/null
+++ b/net/ricketyspace/sicp/one/five.scm
@@ -0,0 +1,13 @@
+;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;; International. See
+;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+(define-module (net ricketyspace sicp one five)
+  #:export (p test))
+
+(define (p) (p))
+
+(define (test x y)
+  (if (= x 0)
+      0
+      y))
diff --git a/net/ricketyspace/sicp/one/fourteen.scm b/net/ricketyspace/sicp/one/fourteen.scm
new file mode 100644
index 0000000..923c088
--- /dev/null
+++ b/net/ricketyspace/sicp/one/fourteen.scm
@@ -0,0 +1,43 @@
+;;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;;; International. See
+;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+;;; adapted from section 1.2.2
+;;; intolerable scheme drivel; ignore it.
+
+(define-module (net ricketyspace sicp one fourteen)
+  #:export (get-cc
+            cc-range
+            cc-diff-list))
+
+(define (get-cc)
+  (let ((no-of-steps 0))
+    (define (cc amount kinds-of-coins)
+      (set! no-of-steps (1+ no-of-steps))
+      (cond ((= amount 0) 1)
+            ((or (< amount 0) (= kinds-of-coins 0)) 0)
+            (else (+ (cc amount
+                         (- kinds-of-coins 1))
+                     (cc (- amount
+                            (first-denomination kinds-of-coins))
+                         kinds-of-coins)))))
+    (define (first-denomination kinds-of-coins)
+      (cond ((= kinds-of-coins 1) 1)
+            ((= kinds-of-coins 2) 5)
+            ((= kinds-of-coins 3) 10)
+            ((= kinds-of-coins 4) 25)
+            ((= kinds-of-coins 5) 50)))
+    (lambda (amount)
+      (cc amount 5)
+      no-of-steps)))
+
+(define (cc-range amount limit incr)
+  (cond ((> amount limit) '())
+        ((<= amount limit)
+         (cons ((get-cc) amount)
+              (cc-range (+ amount incr) limit incr)))))
+
+(define (cc-diff-list l)
+  (cond ((= (length l) 1) '())
+        ((> (length l) 1) (cons (+ (* -1 (car l)) (cadr l))
+                                (cc-diff-list (cdr l))))))
diff --git a/net/ricketyspace/sicp/one/seven.scm b/net/ricketyspace/sicp/one/seven.scm
new file mode 100644
index 0000000..9bda339
--- /dev/null
+++ b/net/ricketyspace/sicp/one/seven.scm
@@ -0,0 +1,49 @@
+;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;; International. See
+;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+(define-module (net ricketyspace sicp one seven)
+  #:export (tolerances-and-sqrt
+            good-enough-alt?
+            sqrt-iter-alt
+            sqrt-sicp-alt))
+
+(use-modules (one six))
+
+;;;; start yak shaving
+(define (gen-good-enough tolerance)
+  (lambda (guess x)
+    (< (abs (- (square guess) x)) tolerance)))
+
+(define (sqrt-iter-with-tolerance guess x tolerance)
+  (let ((good-enough? (gen-good-enough tolerance)))
+    (if (good-enough? guess x)
+        guess
+        (sqrt-iter-with-tolerance (improve guess x)
+                   x tolerance))))
+
+(define (sqrt-with-tolerance x tolerance)
+ (sqrt-iter-with-tolerance 1.0 x tolerance))
+
+(define (tolerances-and-sqrt x tolerance)
+  (let* ((guile-sqrt (sqrt x))
+         (custom-sqrt (sqrt-with-tolerance x tolerance)))
+    (if (eqv? guile-sqrt custom-sqrt)
+        (cons tolerance custom-sqrt)
+        (cons (cons tolerance custom-sqrt)
+              (tolerances-and-sqrt x (/ tolerance 10))))))
+;;;; end yak shaving
+
+;;; start excercise 1.1.7
+(define (good-enough-alt? guess prev-guess)
+  (< (abs (- guess prev-guess)) 0.001))
+
+(define (sqrt-iter-alt guess prev-guess x)
+  (if (good-enough-alt? guess prev-guess)
+      guess
+      (sqrt-iter-alt (improve guess x) guess
+                     x)))
+
+(define (sqrt-sicp-alt x)
+  (sqrt-iter-alt 1.0 2.0 x))
+;;;; end excercise 1.1.7
diff --git a/net/ricketyspace/sicp/one/six.scm b/net/ricketyspace/sicp/one/six.scm
new file mode 100644
index 0000000..c1125ec
--- /dev/null
+++ b/net/ricketyspace/sicp/one/six.scm
@@ -0,0 +1,40 @@
+;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;; International. See
+;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+(define-module (net ricketyspace sicp one six)
+   #:export (sqrt-sicp sqrt-nif square good-enough? new-if improve))
+
+(define (square x)
+  (* x x))
+
+(define (good-enough? guess x)
+  (< (abs (- (square guess) x)) 0.001))
+
+(define (average x y)
+  (/ (+ x y) 2))
+
+(define (improve guess x)
+  (average guess (/ x guess)))
+
+(define (new-if predicate then-clause else-clause)
+  (cond (predicate then-clause)
+        (else else-clause)))
+
+(define (sqrt-iter guess x)
+  (if (good-enough? guess x)
+          guess
+          (sqrt-iter (improve guess x)
+                     x)))
+
+(define (sqrt-iter-nif guess x)
+  (new-if (good-enough? guess x)
+          guess
+          (sqrt-iter-nif (improve guess x)
+                         x)))
+
+(define (sqrt-sicp x)
+  (sqrt-iter 1.0 x))
+
+(define (sqrt-nif x)
+  (sqrt-iter-nif 1.0 x))
diff --git a/net/ricketyspace/sicp/one/three.scm b/net/ricketyspace/sicp/one/three.scm
new file mode 100644
index 0000000..3546fc9
--- /dev/null
+++ b/net/ricketyspace/sicp/one/three.scm
@@ -0,0 +1,36 @@
+;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;; International. See
+;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+(define-module (net ricketyspace sicp one three)
+  #:export (square sum-of-squares largest first-arg-2nd-largest-p
+                   sum-of-squares-of-largest-two))
+
+(define (square x) (* x x))
+
+(define (sum-of-squares x y)
+  (+ (square x) (square y)))
+
+(define (largest x y z)
+  (cond ((and (>= x y)
+              (>= x z)) x)
+        ((and (>= y x)
+              (>= y z)) y)
+        ((and (>= z x)
+              (>= z y)) z)))
+
+(define (first-arg-2nd-largest-p x y z)
+  (or (and (>= x y)
+           (<= x z))
+      (and (<= x y)
+           (>= x z))
+      ))
+
+(define (sum-of-squares-of-largest-two x y z)
+  (sum-of-squares (largest x y z)
+                  (cond ((first-arg-2nd-largest-p x y z)
+                         x)
+                        ((first-arg-2nd-largest-p y x z)
+                         y)
+                        ((first-arg-2nd-largest-p z x y)
+                         z))))
diff --git a/net/ricketyspace/sicp/one/twelve.scm b/net/ricketyspace/sicp/one/twelve.scm
new file mode 100644
index 0000000..7d31561
--- /dev/null
+++ b/net/ricketyspace/sicp/one/twelve.scm
@@ -0,0 +1,58 @@
+;;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;;; International. See
+;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+;;;  ____________________________
+;;; < pascal's fucking triangle. >
+;;; ----------------------------
+;;;  \                 __
+;;;   \               (--)
+;;;    \              (  )
+;;;     \             /--\
+;;;       __         / \  \
+;;;      U--U\.'@@@@@@`.\  )
+;;;      \__/(@@@@@@@@@@) /
+;;;           (@@@@@@@@)((
+;;;           `YY~~~~YY' \\
+;;;            ||    ||   >>
+;;;
+
+(define-module (net ricketyspace sicp one twelve)
+  #:export (compute-triangle
+            compute-line
+            display-line
+            value-at
+            print-triangle
+            print-line))
+
+(define (compute-triangle n)
+  (cond ((= n 1) (list (compute-line n 1)))
+        (else (cons (compute-line n 1)
+                    (compute-triangle (- n 1))))))
+
+(define (compute-line n pos)
+  (cond ((> pos n) '())
+        (else
+         (cons (value-at n pos)
+               (compute-line n (+ pos 1))))))
+
+(define (value-at line pos)
+  (cond ((= line 1) 1)
+        ((= pos 1) 1)
+        ((= line pos) 1)
+        (else (+
+               (value-at (- line 1) (- pos 1))
+               (value-at (- line 1) pos)))))
+
+;;;; printing
+
+(define (print-triangle tl level)
+  (cond ((= (length tl) 0) #t)
+        (else
+         (print-triangle (cdr tl) (+ 1 level))
+         (print-line (car tl) level))))
+
+(define (print-line l level)
+  (let* ((l (map number->string l))
+        (line (string-join l)))
+    (format #t "~a\n" line)))