Implemented strings.

[scheme.forth.jl.git] / scheme.4th

diff --git a/scheme.4th b/scheme.4th
index 8c84378..cb02a3d 100644 (file)
--- a/scheme.4th
+++ b/scheme.4th
@@ -7,8 +7,10 @@ include defer-is.4th
 0 constant number-type
 1 constant boolean-type
 2 constant character-type
-3 constant nil-type
-4 constant pair-type
+3 constant string-type
+4 constant nil-type
+5 constant pair-type
+6 constant symbol-type
 : istype? ( obj -- obj b )
     over = ;
 
@@ -32,6 +34,19 @@ variable nextfree
     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
@@ -198,6 +213,8 @@ parse-idx-stack parse-idx-sp !
 : pair? ( -- bool )
     nextchar [char] ( = ;
 
+: string? ( -- bool )
+    nextchar [char] " = ;
 
 : readnum ( -- num-atom )
     minus? dup if
@@ -243,10 +260,41 @@ parse-idx-stack parse-idx-sp !
     inc-parse-idx
 ;
 
+: readstring ( -- str-obj )
+    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
+;
+
 defer read
 
 : readpair ( -- obj )
-    inc-parse-idx
     eatspaces
 
     \ Empty lists
@@ -259,7 +307,9 @@ defer read
             reset-term abort
         then
 
-        nil-type exit
+        dec-parse-idx
+
+        0 nil-type exit
     then
 
     \ Read first pair element
@@ -277,16 +327,17 @@ defer read
         then
 
         eatspaces read
-
     else
         recurse
     then
 
+    eatspaces
+
     cons
 ;
 
 \ Parse a scheme expression
-: (read) ( -- obj )
+:noname ( -- obj )
 
     eatspaces
 
@@ -305,8 +356,36 @@ 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
+
     pair? if
+        inc-parse-idx
+
+        eatspaces
+
         readpair
+
+        eatspaces
+
+        nextchar [char] ) <> if
+            bold red ." Missing closing paren." reset-term cr
+            abort
+        then
+
+        inc-parse-idx
+
         exit
     then
 
@@ -319,9 +398,8 @@ defer read
     nextchar emit
     ." '. Aborting." reset-term cr
     abort
-;
 
-' (read) is read
+; is read
 
 \ ---- Eval ----
 
@@ -329,13 +407,15 @@ defer read
     number-type istype? if true exit then
     boolean-type istype? if true exit then
     character-type istype? if true exit then
+    string-type istype? if true exit then
     nil-type istype? if true exit then
     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
@@ -343,7 +423,7 @@ defer read
 
 \ ---- Print ----
 
-: printnum ( numobj -- ) drop . ;
+: printnum ( numobj -- ) drop 0 .R ;
 
 : printbool ( numobj -- )
     drop if
@@ -364,19 +444,48 @@ 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 ;
+
 : printnil ( nilobj -- )
-    drop ." ()" ;
+    2drop ." ()" ;
+
+defer print
+: printpair ( pairobj -- )
+    2dup
+    car print
+    cdr
+    nil-type istype? if 2drop exit then
+    pair-type istype? if space recurse exit then
+    ."  . " print
+;
 
-: print ( obj -- )
-    ." ; "
+:noname ( obj -- )
     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
     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 ----
 
@@ -390,7 +499,7 @@ defer read
         cr bold fg green ." > " reset-term
         read
         eval
-        fg cyan print reset-term
+        fg cyan ." ; " print reset-term
     again
 ;