From: Tim Vaughan <tgvaughan@gmail.com>
Date: Sun, 6 Nov 2016 00:12:59 +0000 (+1300)
Subject: Implemented let as macro.
X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?p=scheme.forth.jl.git;a=commitdiff_plain;h=55761030cc43072bbc8b2d1ef5a053fc64a6a3ec

Implemented let as macro.
---

diff --git a/scheme-library.scm b/scheme-library.scm
index 1a68a10..5ee0b49 100644
--- a/scheme-library.scm
+++ b/scheme-library.scm
@@ -7,6 +7,12 @@
 (define (null? args)
   (eq? args ()))
 
+(define (caar l) (car (car l)))
+(define (cadr l) (car (cdr l)))
+(define (cdar l) (cdr (car l)))
+(define (cddr l) (cdr (cdr l)))
+(define (cadar l) (car (cdr (car l))))
+
 ; Join two lists together
 (define (join l1 l2)
   (if (null? l1)
@@ -29,12 +35,32 @@
 
 ;; LIBRARY FORMS
 
+
+; let
+
+(define (let-vars args)
+  (if (null? args)
+    '()
+    (cons (caar args) (let-vars (cdr args)))))
+
+(define (let-inits args)
+  (if (null? args)
+    '()
+  (cons (cadar args) (let-inits (cdr args)))))
+
+(define-macro (let args . body)
+              `((lambda ,(let-vars args)
+                 ,@body) ,@(let-inits args)))
+
+; while
+
 (define-macro (while condition . body)
+              (define loop (gensym))
               `(begin
-                 (define (loop)
+                 (define (,loop)
                    (if ,condition
-                     (begin ,@body (loop))))
-                 (loop)))
+                     (begin ,@body (,loop))))
+                 (,loop)))
 
 ;; TESTING
 
diff --git a/scheme-primitives.4th b/scheme-primitives.4th
index 86fbbd9..38fe2e0 100644
--- a/scheme-primitives.4th
+++ b/scheme-primitives.4th
@@ -1,4 +1,4 @@
-( ==== Type predicates ==== )
+\ ==== Type predicates ==== {{{
 
 :noname ( args -- boolobj )
     2dup 1 ensure-arg-count
@@ -48,7 +48,9 @@
     car primitive-proc-type istype? -rot 2drop boolean-type
 ; make-primitive procedure?
 
-( ==== Type conversions ==== )
+\ }}}
+
+\ ==== Type conversions ==== {{{
 
 :noname ( args -- fixnum )
     2dup 1 ensure-arg-count
@@ -153,7 +155,9 @@
     charlist>symbol
 ; make-primitive string->symbol
 
-( ==== Arithmetic ==== )
+\ }}}
+
+\ ==== Arithmetic ==== {{{
 
 : add-prim ( args -- fixnum )
     2dup nil objeq? if
@@ -284,7 +288,9 @@ variable relcfa
 
 hide relcfa
 
-( ==== Pairs and Lists ==== )
+\ }}}
+
+\ ==== Pairs and Lists ==== {{{
 
 :noname ( args -- pair )
     2dup 2 ensure-arg-count
@@ -297,21 +303,21 @@ hide relcfa
     \ args is already a list!
 ; make-primitive list
 
-:noname ( args -- pair )
+:noname ( args -- obj )
     2dup 1 ensure-arg-count
     car pair-type ensure-arg-type
 
     car
 ; make-primitive car
 
-:noname ( args -- pair )
+:noname ( args -- obj )
     2dup 1 ensure-arg-count
     car pair-type ensure-arg-type
 
     cdr
 ; make-primitive cdr
 
-:noname ( args -- pair )
+:noname ( args -- ok )
     2dup 2 ensure-arg-count
     2dup cdr car
     2swap car pair-type ensure-arg-type
@@ -321,7 +327,7 @@ hide relcfa
     ok-symbol
 ; make-primitive set-car!
 
-:noname ( args -- pair )
+:noname ( args -- ok )
     2dup 2 ensure-arg-count
     2dup cdr car
     2swap car pair-type ensure-arg-type
@@ -331,7 +337,9 @@ hide relcfa
     ok-symbol
 ; make-primitive set-cdr!
 
-( ==== Polymorphic equality testing ==== )
+\ }}}
+
+\ ==== Polymorphic equality testing ==== {{{
 
 :noname ( args -- bool )
     2dup 2 ensure-arg-count
@@ -341,7 +349,9 @@ hide relcfa
     objeq? boolean-type
 ; make-primitive eq?
 
-( ==== Input/Output ==== )
+\ }}}
+
+\ ==== Input/Output ==== {{{
 
 :noname ( args -- finalResult )
     2dup 1 ensure-arg-count
@@ -434,7 +444,9 @@ defer display
     none
 ; make-primitive newline
 
-( ==== Evaluation ==== )
+\ }}}
+
+\ ==== Evaluation ==== {{{
 
 :noname ( args -- result )
     2dup car 2swap cdr
@@ -444,8 +456,11 @@ defer display
     apply
 ; make-primitive apply 
 
-( ==== Error System ==== )
+\ }}}
+
+\ ==== Miscellaneous  ==== {{{
 
+( Produce a recoverable exception. )
 :noname ( args -- result )
     bold fg red
 
@@ -459,3 +474,15 @@ defer display
 
     recoverable-exception throw
 ; make-primitive error
+
+( Generate a temporary unique symbol. Used in the creation of hygienic macros. )
+:noname ( args -- result )
+    0 ensure-arg-count
+
+    [char] _  character-type nil cons
+    drop symbol-type
+; make-primitive gensym
+
+\ }}}
+
+\ vim:fdm=marker
diff --git a/scheme.4th b/scheme.4th
index 95c621a..f8dd089 100644
--- a/scheme.4th
+++ b/scheme.4th
@@ -139,11 +139,6 @@ variable nextfree
     cdr-cells + !
 ;
 
-: caar car car ;
-: cadr cdr car ;
-: cdar car cdr ;
-: cddr cdr cdr ;
-
 : nil 0 nil-type ;
 : nil? nil-type istype? ;
 
@@ -1058,7 +1053,7 @@ parse-idx-stack parse-idx-sp !
     quote-symbol tagged-list?  ;
 
 : quote-body ( quote-obj -- quote-body-obj )
-    cadr ;
+    cdr car ;
 
 : quasiquote? ( obj -- obj bool )
     quasiquote-symbol tagged-list? ;