Add basic implementation of srfi 27

Makefile

@@ -36,6 +36,7 @@ SMODULES = \
   scheme/cyclone/util \
   srfi/9 \
   srfi/18 \
+  srfi/27 \
   srfi/69
 SLDFILES = $(addsuffix .sld, $(SMODULES))
 COBJECTS=$(SLDFILES:.sld=.o)

srfi/27.sld

@@ -0,0 +1,95 @@
+
+;; Copyright 2016 Jason K. MacDuffie
+;; License: MIT (Expat) License
+;;
+;; Right now this uses an LCG, and should probably be replaced
+;; with a higher-quality implementation as soon as possible.
+;; For casual use this will work OK.
+
+(define-library (srfi 27)
+  (import (scheme base)
+          (scheme case-lambda)
+          (scheme time))
+  (export random-integer random-real default-random-source
+          make-random-source random-source?
+          random-source-state-ref random-source-state-set!
+          random-source-randomize! random-source-pseudo-randomize!
+          random-source-make-integers random-source-make-reals)
+  (begin
+    ;; Numbers taken from bsd random
+    (define mult 1103515245)
+    (define incr 12345)
+    (define m 536870912)
+    ;; Cutting off seems like a good idea
+    (define cutoff 100)
+
+    (define-c next-lcg
+      "(void *data, int argc, closure _, object k, object seed)"
+      "object result = NULL;
+       unsigned int s = obj_obj2int(seed);
+       unsigned int mult = 1103515245;
+       unsigned int incr = 12345;
+       unsigned int m = 536870912;
+       unsigned int next_seed = ((s * mult) + incr) % m;
+       result = obj_int2obj(next_seed);
+       return_closcall1(data, k, result);")
+
+    (define-record-type <random-source>
+      (raw-random-source n)
+      random-souce?
+      (n random-source-val set-random-source-val!))
+    
+    (define (make-random-source)
+      (raw-random-source incr))
+    
+    (define (random-source-make-integers s)
+      (lambda (n)
+        (define nextval
+          (next-lcg (random-source-val s)))
+        (set-random-source-val! s nextval)
+        (modulo nextval n)))
+    
+    (define random-source-make-reals
+      (case-lambda
+        ((s)
+         (random-source-make-reals s (/ m)))
+        ((s unit)
+         (if (not (< 0.0 unit 1.0))
+             (error "unit must be between 0.0 and 1.0 (exclusive), but got " unit))
+         (let ((numgen (random-source-make-integers s)))
+           (define r (exact (floor (/ unit))))
+           (lambda ()
+             (* (numgen r) unit))))))
+    
+    (define default-random-source (make-random-source))
+    
+    (define random-integer
+      (random-source-make-integers default-random-source))
+    
+    (define random-real
+      (random-source-make-reals default-random-source))
+    
+    (define (random-source-state-ref s)
+      ;; Just return the integer
+      (random-source-val s))
+    
+    (define (random-source-state-set! s state)
+      ;; Just set the integer
+      (set-random-source-val! s state))
+    
+    (define (random-source-pseudo-randomize! s i j)
+      ;; Pretty bad quality, upgrade after switch to better gen
+      (define n1
+        ((random-source-make-integers i) m))
+      (define n2
+        ((random-source-make-integers j) m))
+      (define n3
+        (abs (- n1 n2)))
+      (random-source-state-set! s n3))
+    
+    (define (random-source-randomize! s)
+      ;; True randomness would be a good idea here
+      (define i (current-second))
+      (define j (+ (current-second) 2))
+      (random-source-pseudo-randomize! s i j))))
+