Scheme solutions for week 135

3 files changed, 110 insertions, 0 deletions

diff --git a/challenge-135/abigail/README.md b/challenge-135/abigail/README.md
index e10d8fbeda..6178e463fe 100644
--- a/challenge-135/abigail/README.md
+++ b/challenge-135/abigail/README.md
@@ -12,6 +12,7 @@
 * [Perl](perl/ch-1.pl)
 * [Python](python/ch-1.py)
 * [Ruby](ruby/ch-1.rb)
+* [Scheme](scheme/ch-1.scm)
 * [Tcl](tcl/ch-1.tcl)
 
 ## Part 2
@@ -26,4 +27,5 @@
 * [Perl](perl/ch-2.pl)
 * [Python](python/ch-2.py)
 * [Ruby](ruby/ch-2.rb)
+* [Scheme](scheme/ch-2.scm)
 * [Tcl](tcl/ch-2.tcl)
diff --git a/challenge-135/abigail/scheme/ch-1.scm b/challenge-135/abigail/scheme/ch-1.scm
new file mode 100644
index 0000000000..1b391cd159
--- /dev/null
+++ b/challenge-135/abigail/scheme/ch-1.scm
@@ -0,0 +1,41 @@
+;;;
+;;; See ../README.md
+;;;
+
+;;;
+;;; Run as: guile --no-auto-compile ch-1.scm < input-file
+;;;
+
+(use-modules (ice-9 regex))
+(use-modules (ice-9 rdelim))
+
+(define (main)
+    (define line (read-line))
+    (define is-number)
+    (define number)
+    (define ll)
+    (if (not (eof-object? line))
+        (begin
+            (set! is-number (string-match "^[-+]?([0-9]+)$" line))
+            (if (not is-number)
+                (display "not an integer")
+                (begin
+                    (set! number (match:substring is-number 1))
+                    (set! ll (string-length number))
+                    (if (= (modulo ll 2) 0)
+                        (display "even number of digits")
+                        (if (< ll 3)
+                            (display "too short")
+                            (display (substring number (/ (- ll 3) 2)
+                                                       (/ (+ ll 3) 2)))
+                        )
+                    )
+                )
+            )
+            (newline)
+            (main)
+        )
+    )
+)
+
+(main)
diff --git a/challenge-135/abigail/scheme/ch-2.scm b/challenge-135/abigail/scheme/ch-2.scm
new file mode 100644
index 0000000000..f5c29b5dac
--- /dev/null
+++ b/challenge-135/abigail/scheme/ch-2.scm
@@ -0,0 +1,67 @@
+;;;
+;;; See ../README.md
+;;;
+
+;;;
+;;; Run as: guile --no-auto-compile ch-2.scm < input-file
+;;;
+
+(use-modules (ice-9 regex))
+(use-modules (ice-9 rdelim))
+(use-modules (ice-9 iconv))
+(use-modules (rnrs bytevectors))
+(use-modules (srfi srfi-1))
+
+(define pat   "^[0-9BCDFGHJKLMNPQRSTVWXYZ]{6}[0-9]$")
+(define w     (list 1 3 1 7 3 9 1))
+
+
+;;
+;; Create a procedure 'byte->val'. It takes the ASCII value of a
+;; character, and returns the corresponding number for the SEDOL
+;; checksum (-10 for "A" .. "Z").
+;;
+(define ords  (bytevector->u8-list (string->bytevector "09A" "UTF-8")))
+(define ord-0 (list-ref ords 0))
+(define ord-9 (list-ref ords 1))
+(define ord-A (list-ref ords 2))
+(define (byte->val b)
+    (if (<= b ord-9)
+        (-  b ord-0)
+        (-  b ord-A)))
+
+
+(define (main)
+    (define sedol (read-line))
+    (define is-sedol)
+    (define valid 0)
+    (define check 0)
+    (define values)
+    (if (not (eof-object? sedol))
+        (begin
+            (set! valid 0)
+            (set! check 0)
+            (set! is-sedol (string-match pat sedol))
+            (if (regexp-match? is-sedol)
+                (begin
+                    (set! values
+                        (map-in-order byte->val
+                            (bytevector->u8-list 
+                                (string->bytevector
+                                    (match:substring is-sedol 0) "UTF-8"))))
+                    (set! check
+                        (fold (lambda (weight val sum) (+ sum (* weight val)))
+                              0 w values))
+                    ;;
+                    ;; A SEDOL is valid iff the checksum is a multiple of 10
+                    ;;
+                    (if (= 0 (modulo check 10)) (set! valid 1))
+                )
+            )
+            (display valid)(newline)
+            (main)
+        )
+    )
+)
+
+(main)