From 17d72f2cea851ece989b965af6a58559a0407196 Mon Sep 17 00:00:00 2001
From: Linus <bjornstam.linus@fastmail.se>
Date: Mon, 9 Nov 2020 22:57:18 +0100
Subject: [PATCH] Added generator sequences

Basic hack of in-cycle and in-indexed
---
 goof.scm      |  8 +++---
 iterators.scm | 70 +++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 71 insertions(+), 7 deletions(-)

diff --git a/goof.scm b/goof.scm
index 673137d..82b83a6 100644
--- a/goof.scm
+++ b/goof.scm
@@ -35,7 +35,9 @@
 
 
 (use-modules (helpers)
-             (srfi srfi-71))
+             ((srfi srfi-1) #:select (circular-list))
+             (srfi srfi-71)
+             (rnrs io simple))
 
 (define-aux-syntaxes
   ;; Auxiliary syntax for the loop clauses
@@ -101,13 +103,9 @@
      (cl orig name l a v c r f ((cur-ul ... (:let id id* ... expr)) . ul-rest) uw ub (clauses ...) . body))
     ((_ orig name l a v c r f ((cur-ul ...) . ul-rest) uw ub (:let* (id id* ... expr) clauses ...) . body)
      (cl orig name l a v c r f ((cur-ul ... (:let* id id* ... expr)) . ul-rest) (clauses ...) . body))
-
     ;; Explicit subloop. Shorthand for (:when #t)
     ((_ orig name l a v c r f ul ((cur-uw ...) . uw-rest) ub (:subloop clauses ...) . body)
      (cl orig name l a v c r f ul ((cur-uw ... #t) . uw-rest) ub (clauses ...) . body))
-
-
-    
     ;; :for-clauses
     ;; found a for clause when we have a :when or :unless clause. Push new subloop
     ((_ orig name l a v c r f ul ((uw uw* ...) . uw-rest) ub ((for-rest ...) clauses ...) . body)
diff --git a/iterators.scm b/iterators.scm
index 786197c..f59a0a6 100644
--- a/iterators.scm
+++ b/iterators.scm
@@ -47,7 +47,7 @@
    (n () () ((var init step)) (stop) () () . rest))))
 
 (define-syntax in-list
-  (syntax-rules ()
+  (syntax-rules (:gen)
     ((_ ((var) source) next . rest)
      (in-list ((var cursor) source) next . rest))
     ((_       ((var cursor) source) next . rest)
@@ -71,9 +71,25 @@
       ;; final bindings: things bound in the final function.
       ()
       ;; the continuation.
-      . rest))))
+      . rest))
 
+    ;; Generator-clauses
+    ((_ lst)
+     (gen-list lst))
+    ((_ :gen (var) (expr step))
+     (gen-list lst step))))
 
+(define gen-list
+  (case-lambda
+    ((lst)
+     (gen-list lst cdr))
+    ((lst by)
+     (lambda ()
+       (if (null? lst)
+           (eof-object)
+           (let ((res (car lst)))
+             (set! lst (by lst))
+             res))))))
 
 
 (define-syntax in-lists
@@ -342,3 +358,53 @@
   (syntax-rules ()
     ((multiplying args next . rest)
      (accumulating (* (lambda (x) x) 1) args next . rest))))
+
+
+;;; Here starts generator clauses.
+
+(define (generator->list gen)
+  (let ((res (gen)))
+    (if (eof-object? res)
+        '()
+        (cons res (generator->list gen)))))
+
+(define (generator-cycle gen)
+  (let ((circle (apply circular-list (generator->list gen))))
+    (lambda ()
+      (let ((res (car circle)))
+        (set! circle (cdr circle))
+        res))))
+        
+(define-syntax in-cycle
+  (syntax-rules ()
+    ((_ ((id) (source)) n . rest)
+     (n ((gen (generator-cycle source)))
+        ()
+        ((id (gen) (gen)))
+        ((eof-object? id))
+        ()
+        ()
+        . rest))))
+
+
+(define (generator-indexed gen)
+  (let ((i 0))
+    (lambda ()
+      (let ((res (gen)) (index i))
+        (if (eof-object? res)
+            (values res res)
+            (begin
+              (set! i (+ i 1))
+              (values index res)))))))
+
+;; Somewhat of a hack :)
+(define-syntax in-indexed
+  (syntax-rules ()
+    ((_ ((i val) (source)) n . rest)
+     (n ((gen (generator-indexed source)))
+        ()
+        ((i 0 i))
+        ((eof-object? i))
+        ((i val (gen)))
+        ()
+        . rest))))