X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme.4th;h=10e4f2698ea27897d742f8b07899ca4841533d7c;hb=0709203cb8054ba71819df58791725afe2587afe;hp=63a342019a1ac7ed2857029c6ac13058fa3f56ec;hpb=f95f47dbec94087af4452f20e9eca72fb7f299c8;p=scheme.forth.jl.git

diff --git a/scheme.4th b/scheme.4th
index 63a3420..10e4f26 100644
--- a/scheme.4th
+++ b/scheme.4th
@@ -4,14 +4,20 @@ scheme definitions
 include term-colours.4th
 include defer-is.4th
 
+\ ------ Types ------
+
 0 constant number-type
 1 constant boolean-type
 2 constant character-type
-3 constant nil-type
-4 constant pair-type
-: istype? ( obj -- obj b )
+3 constant string-type
+4 constant nil-type
+5 constant pair-type
+6 constant symbol-type
+: istype? ( obj type -- obj bool )
     over = ;
 
+\ ------ Memory ------
+
 100 constant N
 create car-cells N allot
 create car-type-cells N allot
@@ -44,6 +50,20 @@ variable nextfree
     cdr-type-cells + @
 ;
 
+: nil 0 nil-type ;
+: nil? nil-type istype? ;
+
+: objvar create 0 , 0 , ;
+
+: value@ ( objvar -- val ) @ ;
+: type@ ( objvar -- type ) 1+ @ ;
+: value! ( newval objvar -- ) ! ;
+: type! ( newtype objvar -- ) 1+ ! ;
+: setobj ( newobj objvar -- ) dup rot swap 1+ ! ! ; 
+: fetchobj ( objvar -- obj ) dup @ swap 1+ @ ; 
+
+objvar symbol-table
+nil symbol-table setobj
 
 \ ---- Read ----
 
@@ -211,6 +231,32 @@ parse-idx-stack parse-idx-sp !
 : pair? ( -- bool )
     nextchar [char] ( = ;
 
+: string? ( -- bool )
+    nextchar [char] " = ;
+
+: initial? ( -- bool )
+    nextchar [char] A >= nextchar [char] Z <= and if true exit then
+    nextchar [char] a >= nextchar [char] z <= and if true exit then
+    nextchar [char] * = if true exit then
+    nextchar [char] / = if true exit then
+    nextchar [char] > = if true exit then
+    nextchar [char] < = if true exit then
+    nextchar [char] = = if true exit then
+    nextchar [char] ? = if true exit then
+    nextchar [char] ! = if true exit then
+    false
+;
+
+: symbol? ( -- bool )
+    initial? if true exit then
+    nextchar [char] + =
+    nextchar [char] - = or if
+        inc-parse-idx
+        delim? if dec-parse-idx true exit then
+        dec-parse-idx
+    then
+    false
+;
 
 : readnum ( -- num-atom )
     minus? dup if
@@ -256,6 +302,92 @@ parse-idx-stack parse-idx-sp !
     inc-parse-idx
 ;
 
+: readstring ( -- charlist )
+    nextchar [char] " = if
+        inc-parse-idx
+
+        delim? false = if
+            bold fg red
+            ." No delimiter following right double quote. Aborting." cr
+            reset-term abort
+        then
+
+        dec-parse-idx
+
+        0 nil-type exit
+    then
+
+    nextchar [char] \ = if
+        inc-parse-idx
+        nextchar case
+            [char] n of '\n' endof
+            [char] " of [char] " endof
+            [char] \
+        endcase
+    else
+        nextchar
+    then
+    inc-parse-idx character-type
+
+    recurse
+
+    cons
+;
+
+: readsymbol ( -- charlist )
+    delim? if nil exit then
+
+    nextchar inc-parse-idx character-type
+
+    recurse
+
+    cons
+;
+
+: charlist-equiv ( charlist charlist -- bool )
+
+    2over 2over
+
+    \ One or both nil
+    nil? -rot 2drop
+    if
+        nil? -rot 2drop
+        if
+            true exit
+        else
+            false exit
+        then
+    else
+        nil? -rot 2drop
+        if
+            false exit
+        then
+    then
+
+    2over 2over
+
+    \ Neither nil
+    car 2swap car rot = -rot = and if
+            cdr 2swap cdr recurse
+        else
+            2drop 2drop false
+    then
+;
+
+: (symbol-in-table?) ( charlist symbol-table -- charlist symbol-obj )
+
+    begin
+        nil? false =
+    while
+        2over 2over
+        car
+        charlist-equiv if
+    repeat
+;
+
+: symbol-in-table? ( charlist -- charlist bool )
+    symbol-table (symbol-in-table?) ;
+
 defer read
 
 : readpair ( -- obj )
@@ -320,6 +452,30 @@ defer read
         exit
     then
 
+    string? if
+        inc-parse-idx
+        readstring
+        drop string-type
+
+        nextchar [char] " <> if
+            bold red ." Missing closing double-quote." reset-term cr
+            abort
+        then
+
+        inc-parse-idx
+        exit
+    then
+
+    symbol? if
+        readsymbol
+        drop symbol-type
+        2dup
+        symbol-table fetch
+        cons
+        symbol-table set
+        exit
+    then
+
     pair? if
         inc-parse-idx
 
@@ -354,17 +510,13 @@ defer read
 \ ---- Eval ----
 
 : self-evaluating? ( obj -- obj bool )
-    number-type istype? if true exit then
-    boolean-type istype? if true exit then
-    character-type istype? if true exit then
-    nil-type istype? if true exit then
-    false ;
+    true \ everything self-evaluating for now
+;
 
 : eval
-    \ self-evaluating? if
-    \     exit
-    \ then
-    exit
+    self-evaluating? if
+        exit
+    then
 
     bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
     abort
@@ -393,6 +545,31 @@ defer read
     endcase
 ;
 
+: (printstring) ( stringobj -- )
+    nil-type istype? if 2drop exit then
+
+    2dup car drop dup
+    case
+        '\n' of ." \n" drop endof
+        [char] \ of ." \\" drop endof
+        [char] " of [char] \ emit [char] " emit drop endof
+        emit
+    endcase
+
+    cdr recurse
+;
+: printstring ( stringobj -- )
+    [char] " emit
+    (printstring)
+    [char] " emit ;
+
+: printsymbol ( symbolobj -- )
+    nil-type istype? if 2drop exit then
+
+    2dup car drop emit
+    cdr recurse
+;
+
 : printnil ( nilobj -- )
     2drop ." ()" ;
 
@@ -410,6 +587,8 @@ defer print
     number-type istype? if printnum exit then
     boolean-type istype? if printbool exit then
     character-type istype? if printchar exit then
+    string-type istype? if printstring exit then
+    symbol-type istype? if printsymbol exit then
     nil-type istype? if printnil exit then
     pair-type istype? if ." (" printpair ." )" exit then