From 7dcc529e3d85e04807c158fe1c3ca8a339ca6df6 Mon Sep 17 00:00:00 2001
From: Justin Ethier <justin.ethier@gmail.com>
Date: Mon, 22 Jan 2018 18:54:37 -0500
Subject: [PATCH] WIP, testing

---
 match-simple.scm | 163 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 163 insertions(+)
 create mode 100644 match-simple.scm

diff --git a/match-simple.scm b/match-simple.scm
new file mode 100644
index 00000000..667a5dac
--- /dev/null
+++ b/match-simple.scm
@@ -0,0 +1,163 @@
+;; A temporary test file, based on code from:
+;; http://synthcode.com/scheme/match-simple.scm
+(import (scheme base) (scheme write))
+
+(define-syntax match
+  (syntax-rules ()
+    ((match expr (pat . body) ...)
+     (match-gen-labels expr start () (pat . body) ...))))
+
+(define-syntax match-gen-labels
+  (syntax-rules (=>)
+    ((_ expr label ((k1 fk1 pat1 . body1) (k fk pat . body) ...))
+     (let ((tmp expr))
+       (letrec ((k (lambda () (match-one tmp pat (begin . body) (fk)))) ...
+                (label (lambda () (error "no matches" tmp))))
+         (match-one tmp pat1 (begin . body1) (fk1)))))
+    ((_ expr label (labels ...) (pat (=> fk) . body) . rest)
+     (match-gen-labels expr fk (labels ... (label fk pat . body)) . rest))
+    ((_ expr label (labels ...) (pat . body) . rest)
+     (match-gen-labels expr fail (labels ... (label fail pat . body)) . rest))
+    ))
+
+(define-syntax match-one
+  (syntax-rules (_ ___ quote ? and or not)
+    ((match-one var () sk fk)
+     (if (null? var) sk fk))
+    ((match-one var (quote a) sk fk)
+     (if (equal? var 'a) sk fk))
+    ((match-one var (and) sk fk) sk)
+    ((match-one var (and a b ...) sk fk)
+     (match-one var a (match-one var (and b ...) sk fk) fk))
+    ((match-one var (or) sk fk) fk)
+    ((match-one var (or a ...) sk fk)
+     (let ((sk2 (lambda () sk)))
+       (match-one var (not (and (not a) ...)) (sk2) fk)))
+    ((match-one var (not a) sk fk)
+     (match-one var a fk sk))
+    ((match-one var (? pred a ...) sk fk)
+     (if (pred var) (match-one var (and a ...) sk fk) fk))
+    ((match-one var (a ___) sk fk)
+     (match-extract-variables a (match-gen-ellipses var a sk fk) ()))
+    ((match-one var (a) sk fk)
+     (if (and (pair? var) (null? (cdr var)))
+       (let ((tmp (car var)))
+         (match-one tmp a sk fk))
+       fk))
+    ((match-one var (a . b) sk fk)
+     (if (pair? var)
+       (let ((tmp1 (car var)))
+         (match-one tmp1 a (let ((tmp2 (cdr var))) (match-one tmp2 b sk fk)) fk))
+       fk))
+    ((match-one var #(a ...) sk fk)
+     (if (vector? var)
+       (let ((ls (vector->list var)))
+         (match-one ls (a ...) sk fk))
+       fk))
+    ((match-one var _ sk fk) sk)
+    ((match-one var x sk fk)
+     (let-syntax ((sym?
+                   (syntax-rules ()
+                     ((sym? x) (let ((x var)) sk))
+                     ((sym? y) (if (equal? var x) sk fk)))))
+       (sym? abracadabra)))  ; thanks Oleg
+    ))
+
+(define-syntax match-gen-ellipses
+  (syntax-rules ()
+    ((_ var a sk fk ((v v-ls) ...))
+     (let loop ((ls var) (v-ls '()) ...)
+       (cond ((null? ls)
+              (let ((v (reverse v-ls)) ...) sk))
+             ((pair? ls)
+              (let ((x (car ls)))
+                (match-one x a (loop (cdr ls) (cons v v-ls) ...) fk)))
+             (else
+              fk))))
+    ))
+
+(define-syntax match-extract-variables
+  (syntax-rules (_ ___ quote ? and or not)
+    ((_ (a . b) k v)
+     (match-extract-variables a (match-extract-variables-step b k v) ()))
+    ((_ #(a ...) k v)
+     (match-extract-variables (a ...) k v))
+    ((_ a (k ...) (v ...))
+     (let-syntax ((sym?
+                   (syntax-rules ()
+                     ((sym? a) (k ... (v ... (a a-ls))))
+                     ((sym? b) (k ... (v ...))))))
+       (sym? abracadabra)))
+    ))
+
+(define-syntax match-extract-variables-step
+  (syntax-rules ()
+    ((_ a k (v ...) (v2 ...))
+     (match-extract-variables a k (v ... v2 ...)))))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; gimme some sugar baby
+
+(define-syntax match-lambda
+  (syntax-rules ()
+    ((_ clause ...) (lambda (expr) (match expr clause ...)))))
+
+;(define-syntax match-lambda*
+;  (syntax-rules ()
+;    ((_ clause ...) (lambda expr (match expr clause ...)))))
+;
+;(define-syntax match-let
+;  (syntax-rules ()
+;    ((_ ((pat expr)) . body)
+;     (match expr (pat . body)))
+;    ((_ ((pat expr) ...) . body)
+;     (match (list expr ...) ((pat ...) . body)))
+;    ((_ loop . rest)
+;     (match-named-let loop () . rest))
+;    ))
+;
+;(define-syntax match-named-let
+;  (syntax-rules ()
+;    ((_ loop ((pat expr var) ...) () . body)
+;     (let loop ((var expr) ...)
+;       (match-let ((pat var) ...)
+;         . body)))
+;    ((_ loop (v ...) ((pat expr) . rest) . body)
+;     (match-named-let loop (v ... (pat expr tmp)) rest . body))
+;    ))
+;
+;(define-syntax match-letrec
+;  (syntax-rules ()
+;    ((_ vars . body) (match-letrec-helper () vars . body))))
+;
+;(define-syntax match-letrec-helper
+;  (syntax-rules ()
+;    ((_ ((pat expr var) ...) () . body)
+;     (letrec ((var expr) ...)
+;       (match-let ((pat var) ...)
+;         . body)))
+;    ((_ (v ...) ((pat expr) . rest) . body)
+;     (match-letrec-helper (v ... (pat expr tmp)) rest . body))
+;    ))
+;
+;(define-syntax match-let*
+;  (syntax-rules ()
+;    ((_ () . body)
+;     (begin . body))
+;    ((_ ((pat expr) . rest) . body)
+;     (match expr (pat (match-let* rest . body))))))
+;
+;(define tst
+;  (match-lambda
+;     ((a b) (vector 'fromlist a b))
+;     ((? string? x) x)
+;     ((X #f))))
+;
+;(display (match (list 1 2 3) ((a b c) b)))
+;(display (tst '(1 2)))
+;(display (tst "gehtdurch"))
+;(display (tst 42))
+
+(display (match "test" ((? string? x) x)))
+
+