X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme.4th;h=524f3a1fccf4f31c3ffcb63fc7a81bed226c7fec;hb=35aac989c77e879267931748dca2ca1da01d4e08;hp=061d36d4deec6047d0e5bbd9a2a13484794c6282;hpb=265928153dc137aef799ad21eaaaaa71103d6c91;p=scheme.forth.jl.git

diff --git a/scheme.4th b/scheme.4th
index 061d36d..524f3a1 100644
--- a/scheme.4th
+++ b/scheme.4th
@@ -6,33 +6,48 @@ scheme definitions
 include term-colours.4th
 
 0 constant number-type
+1 constant boolean-type
+2 constant character-type
 : istype? ( obj -- obj b )
     over = ;
 
 \ ---- Read ----
 
 variable parse-idx
-variable dummy-parse-idx
+variable stored-parse-idx
+create parse-str 161 allot
+variable parse-str-span
+
+: append-newline
+    1 parse-str-span +!
+    '\n' parse-str parse-str-span @ + ! ;
+
+: getline
+    parse-str 160 expect
+    span @ parse-str-span !
+    append-newline
+    0 parse-idx ! ;
+
+: inc-parse-idx
+    1 parse-idx +! ;
+
+: dec-parse-idx
+    1 parse-idx -! ;
 
 : store-parse-idx
-    parse-idx @ dummy-parse-idx !  ;
+    parse-idx @ stored-parse-idx !  ;
 
 : restore-parse-idx
-    dummy-parse-idx @ parse-idx !  ;
+    stored-parse-idx @ parse-idx !  ;
 
-variable parse-str
 
 : charavailable? ( -- bool )
-    parse-str @ @ parse-idx @ >
+    parse-str-span @ parse-idx @ >
 ;
 
 : nextchar ( -- char )
-    charavailable? if
-        parse-str @ 1+ parse-idx @ + @
-    else
-        0
-    then
-;
+    charavailable? false = if getline then
+    parse-str parse-idx @ + @ ;
 
 : whitespace? ( -- bool )
     nextchar BL = 
@@ -49,7 +64,7 @@ variable parse-str
     begin
         whitespace?
     while
-            1 parse-idx +!
+        inc-parse-idx
     repeat
 ;
 
@@ -68,10 +83,10 @@ variable parse-str
     then
 
     store-parse-idx
-    1 parse-idx +!
+    inc-parse-idx
 
     begin digit? while
-        1 parse-idx +!
+        inc-parse-idx
     repeat
 
     delim? charavailable? false = or if
@@ -83,16 +98,45 @@ variable parse-str
     then
 ;
 
+: boolean? ( -- bool )
+    nextchar [char] # <> if false exit then
+
+    store-parse-idx
+    inc-parse-idx
+
+    nextchar [char] t <>
+    nextchar [char] f <>
+    and if restore-parse-idx false exit then
+
+    restore-parse-idx
+    true
+;
+
+: character? ( -- bool )
+    nextchar [char] # <> if false exit then
+
+    store-parse-idx
+    inc-parse-idx
+
+    nextchar [char] \ <> if restore-parse-idx false exit then
+
+    inc-parse-idx
+
+    charavailable? false = if restore-parse-idx false exit then
+
+    restore-parse-idx true
+;
+
 : readnum ( -- num-atom )
     minus? dup if
-        1 parse-idx +!
+        inc-parse-idx
     then
 
     0
 
     begin digit? while
         10 * nextchar [char] 0 - +
-        1 parse-idx +!
+        inc-parse-idx
     repeat
 
     swap if negate then
@@ -100,73 +144,84 @@ variable parse-str
     number-type
 ;
 
-\ Parse a counted string into a scheme expression
+: readbool ( -- bool-atom )
+    inc-parse-idx
+    
+    nextchar [char] f = if
+        false
+    else
+        true
+    then
+
+    boolean-type
+;
+
+\ Parse a scheme expression
 : read ( -- obj )
 
     eatspaces
+
     number? if
         readnum
         exit
     then
 
-    ." Error parsing string at character" parse-idx ? ." . Aborting." cr
+    boolean? if
+        readbool
+        exit
+    then
+
+    bold fg red ." Error parsing string starting at character '"
+    nextchar emit
+    ." '. Aborting." reset-term cr
     abort
 ;
 
 \ ---- Eval ----
 
 : self-evaluating? ( obj -- obj bool )
-    number-type istype? ;
+    number-type istype? if true exit then
+    boolean-type istype? if true exit then
+    false ;
 
 : eval
     self-evaluating? if
         exit
     then
 
-    ." Error evaluating expression - unrecognized type. Aborting." cr
+    bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
     abort
 ;
 
 \ ---- Print ----
 
-: print ( obj -- )
-    number-type istype? if
-        drop .
+: printnum ( numobj -- ) drop . ;
+
+: printbool ( numobj -- )
+    drop if
+        ." #t"
+    else
+        ." #f"
     then
 ;
 
-\ ---- REPL ----
-
-create repl-buffer 161 allot
-repl-buffer parse-str !
-
-: getline
-    repl-buffer 1+ 160 expect cr span @ repl-buffer ! ;
+: print ( obj -- )
+    ." ; "
+    number-type istype? if ." => " printnum exit then
+    boolean-type istype? if ." => " printbool exit then
+;
 
-: eof?
-    repl-buffer @ 0= if false exit then
-    repl-buffer 1+ @ 4 <> if false exit then
-    true ;
+\ ---- REPL ----
 
 : repl
     cr ." Welcome to scheme.forth.jl!" cr
        ." Use Ctrl-D to exit." cr
 
     begin
-        cr bold fg green ." => " reset-term
-        getline
-
-        eof? if
-            fg blue ." Moriturus te saluto." reset-term
-            exit
-        then
-
-        repl-buffer @ 0> if
-            0 parse-idx !
-            read
-            eval
-            print
-        then
+        cr bold fg green ." > " reset-term
+        read
+        eval
+        fg cyan print reset-term
     again
 ;