X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme.4th;h=7fcbb30dd377f85e4e5ffe4bc1cf2e752aed0ace;hb=926748a17c5ba8eca3bc7379d3c52f6e94ef5c36;hp=9a490539ea259917f160903018b578fd1c10f2bc;hpb=62886ccdbb1bba3bf64abfb5b8f01cbf2c7f9f7e;p=scheme.forth.jl.git

diff --git a/scheme.4th b/scheme.4th
index 9a49053..7fcbb30 100644
--- a/scheme.4th
+++ b/scheme.4th
@@ -2,14 +2,49 @@ vocabulary scheme
 scheme definitions
 
 include term-colours.4th
+include defer-is.4th
 
 0 constant number-type
 1 constant boolean-type
 2 constant character-type
 3 constant nil-type
+4 constant pair-type
 : istype? ( obj -- obj b )
     over = ;
 
+100 constant N
+create car-cells N allot
+create car-type-cells N allot
+create cdr-cells N allot
+create cdr-type-cells N allot
+
+variable nextfree
+0 nextfree !
+
+: cons ( car-obj cdr-obj -- pair-obj )
+    cdr-type-cells nextfree @ + !
+    cdr-cells nextfree @ + !
+    car-type-cells nextfree @ + !
+    car-cells nextfree @ + !
+
+    nextfree @ pair-type
+
+    1 nextfree +!
+;
+
+: car ( pair-obj -- car-obj )
+    drop
+    dup car-cells + @ swap
+    car-type-cells + @
+;
+
+: cdr ( pair-obj -- car-obj )
+    drop
+    dup cdr-cells + @ swap
+    cdr-type-cells + @
+;
+
+
 \ ---- Read ----
 
 variable parse-idx
@@ -173,13 +208,8 @@ parse-idx-stack parse-idx-sp !
     pop-parse-idx true
 ;
 
-: empty-list? ( -- bool )
-    nextchar [char] ( <> if false exit then
-    push-parse-idx
-    inc-parse-idx
-    eatspaces
-    nextchar [char] ) <> if pop-parse-idx false exit then
-    pop-parse-idx true ;
+: pair? ( -- bool )
+    nextchar [char] ( = ;
 
 
 : readnum ( -- num-atom )
@@ -226,16 +256,51 @@ parse-idx-stack parse-idx-sp !
     inc-parse-idx
 ;
 
-: readnil ( -- nil-atom )
+defer read
+
+: readpair ( -- obj )
     inc-parse-idx
     eatspaces
-    inc-parse-idx
 
-    nil-type
+    \ Empty lists
+    nextchar [char] ) = if
+        inc-parse-idx
+
+        delim? false = if
+            bold fg red
+            ." No delimiter following right paren. Aborting." cr
+            reset-term abort
+        then
+
+        nil-type exit
+    then
+
+    \ Read first pair element
+    read
+
+    \ Pairs
+    eatspaces
+    nextchar [char] . = if
+        inc-parse-idx
+
+        delim? false = if
+            bold fg red
+            ." No delimiter following '.'. Aborting." cr
+            reset-term abort
+        then
+
+        eatspaces read
+    else
+        recurse
+    then
+
+    eatspaces
+
+    cons
 ;
 
 \ Parse a scheme expression
-: read ( -- obj )
+:noname ( -- obj )
 
     eatspaces
 
@@ -254,8 +319,8 @@ parse-idx-stack parse-idx-sp !
         exit
     then
 
-    empty-list? if
-        readnil
+    pair? if
+        readpair
         exit
     then
 
@@ -268,7 +333,8 @@ parse-idx-stack parse-idx-sp !
     nextchar emit
     ." '. Aborting." reset-term cr
     abort
-;
+
+; is read
 
 \ ---- Eval ----
 
@@ -280,9 +346,10 @@ parse-idx-stack parse-idx-sp !
     false ;
 
 : eval
-    self-evaluating? if
-        exit
-    then
+    \ self-evaluating? if
+    \     exit
+    \ then
+    exit
 
     bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
     abort
@@ -290,7 +357,7 @@ parse-idx-stack parse-idx-sp !
 
 \ ---- Print ----
 
-: printnum ( numobj -- ) drop . ;
+: printnum ( numobj -- ) drop 0 .R ;
 
 : printbool ( numobj -- )
     drop if
@@ -314,13 +381,27 @@ parse-idx-stack parse-idx-sp !
 : printnil ( nilobj -- )
     drop ." ()" ;
 
-: print ( obj -- )
-    ." ; "
+defer print
+: printpair ( pairobj -- )
+    ." ("
+    2dup
+    car print
+    cdr
+    nil-type istype? if 2drop ." )" exit then
+    pair-type istype? if recurse ." )" exit then
+    ."  . " print ." )"
+;
+
+:noname ( obj -- )
     number-type istype? if printnum exit then
     boolean-type istype? if printbool exit then
     character-type istype? if printchar exit then
     nil-type istype? if printnil exit then
-;
+    pair-type istype? if printpair exit then
+
+    bold fg red ." Error printing expression - unrecognized type. Aborting" reset-term cr
+    abort
+; is print
 
 \ ---- REPL ----
 
@@ -334,7 +415,7 @@ parse-idx-stack parse-idx-sp !
         cr bold fg green ." > " reset-term
         read
         eval
-        fg cyan print reset-term
+        fg cyan ." ; " print reset-term
     again
 ;