X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme.4th;h=0bbfbf5435b5d13793c7f800b1fab2bc54951dc7;hb=688fe55448ead0055f80f65e44a97258450c6095;hp=8d9c97a8938a865d92ddf9326379fb027337ec3a;hpb=bc4c866824b12208394e0ca8d6468ed8cd5c49a8;p=scheme.forth.jl.git

diff --git a/scheme.4th b/scheme.4th
index 8d9c97a..0bbfbf5 100644
--- a/scheme.4th
+++ b/scheme.4th
@@ -14,7 +14,41 @@ include term-colours.4th
 \ ---- Read ----
 
 variable parse-idx
-variable dummy-parse-idx
+variable stored-parse-idx
+create parse-str 161 allot
+variable parse-str-span
+
+
+create parse-idx-stack 10 allot 
+variable parse-idx-sp
+parse-idx-stack parse-idx-sp !
+
+: push-parse-idx
+    parse-idx @ parse-idx-sp @ !
+    1 parse-idx-sp +!
+;
+
+: pop-parse-idx
+    parse-idx-sp @ parse-idx-stack <= abort" Parse index stack underflow."
+
+    1 parse-idx-sp -!
+
+    parse-idx-sp @ @ parse-idx ! ;
+
+
+: append-newline
+    '\n' parse-str parse-str-span @ + !
+    1 parse-str-span +! ;
+
+: empty-parse-str
+    0 parse-str-span !
+    0 parse-idx ! ;
+
+: getline
+    parse-str 160 expect cr
+    span @ parse-str-span !
+    append-newline
+    0 parse-idx ! ;
 
 : inc-parse-idx
     1 parse-idx +! ;
@@ -22,30 +56,19 @@ variable dummy-parse-idx
 : dec-parse-idx
     1 parse-idx -! ;
 
-: store-parse-idx
-    parse-idx @ dummy-parse-idx !  ;
-
-: restore-parse-idx
-    dummy-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 = 
-    nextchar '\n' = or
-;
+    nextchar '\n' = or ;
+
+: eof? ( -- bool )
+    nextchar 4 = ;
 
 : delim? ( -- bool )
     whitespace?
@@ -75,18 +98,18 @@ variable parse-str
         exit
     then
 
-    store-parse-idx
+    push-parse-idx
     inc-parse-idx
 
     begin digit? while
         inc-parse-idx
     repeat
 
-    delim? charavailable? false = or if
-        restore-parse-idx
+    delim? if
+        pop-parse-idx
         true
     else
-        restore-parse-idx
+        pop-parse-idx
         false
     then
 ;
@@ -94,30 +117,60 @@ variable parse-str
 : boolean? ( -- bool )
     nextchar [char] # <> if false exit then
 
-    store-parse-idx
+    push-parse-idx
     inc-parse-idx
 
     nextchar [char] t <>
     nextchar [char] f <>
-    and if restore-parse-idx false exit then
+    and if pop-parse-idx false exit then
+
+    inc-parse-idx
+    delim? if
+        pop-parse-idx
+        true
+    else
+        pop-parse-idx
+        false
+    then
+;
+
+: str-equiv? ( str -- bool )
+    push-parse-idx
 
-    restore-parse-idx
     true
+
+    swap dup rot + swap
+    do
+        i @ nextchar <> if
+            drop false
+            leave
+        then
+
+        inc-parse-idx
+    loop
+
+    delim? <> if drop false then
+
+    pop-parse-idx
 ;
 
 : character? ( -- bool )
     nextchar [char] # <> if false exit then
 
-    store-parse-idx
+    push-parse-idx
     inc-parse-idx
 
-    nextchar [char] \ <> if restore-parse-idx false exit then
+    nextchar [char] \ <> if pop-parse-idx false exit then
 
     inc-parse-idx
 
-    charavailable? false = if restore-parse-idx false exit then
+    S" newline" str-equiv? if true exit then
+    S" space" str-equiv? if true exit then
+    S" tab" str-equiv? if true exit then
+
+    charavailable? false = if pop-parse-idx false exit then
 
-    restore-parse-idx true
+    pop-parse-idx true
 ;
 
 : readnum ( -- num-atom )
@@ -146,10 +199,12 @@ variable parse-str
         true
     then
 
+    inc-parse-idx
+
     boolean-type
 ;
 
-\ Parse a counted string into a scheme expression
+\ Parse a scheme expression
 : read ( -- obj )
 
     eatspaces
@@ -164,6 +219,11 @@ variable parse-str
         exit
     then
 
+    eof? if
+        bold fg blue ." Moriturus te saluto." reset-term ."  ok" cr
+        quit
+    then
+
     bold fg red ." Error parsing string starting at character '"
     nextchar emit
     ." '. Aborting." reset-term cr
@@ -200,42 +260,23 @@ variable parse-str
 
 : print ( obj -- )
     ." ; "
-    number-type istype? if ." => " printnum exit then
-    boolean-type istype? if ." => " printbool exit then
+    number-type istype? if printnum exit then
+    boolean-type istype? if printbool exit then
 ;
 
 \ ---- REPL ----
 
-create repl-buffer 161 allot
-repl-buffer parse-str !
-
-: getline
-    repl-buffer 1+ 160 expect span @ repl-buffer ! ;
-
-: eof?
-    repl-buffer @ 0= if false exit then
-    repl-buffer 1+ @ 4 <> if false exit then
-    true ;
-
 : repl
     cr ." Welcome to scheme.forth.jl!" cr
        ." Use Ctrl-D to exit." cr
 
+    empty-parse-str
+
     begin
         cr bold fg green ." > " reset-term
-        getline
-
-        eof? if
-            cr bold fg blue ." Moriturus te saluto." reset-term
-            exit
-        then
-
-        repl-buffer @ 0> if
-            0 parse-idx !
-            read
-            eval
-            fg cyan print reset-term
-        then
+        read
+        eval
+        fg cyan print reset-term
     again
 ;