Better handling of booleans.

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

diff --git a/scheme.4th b/scheme.4th
index 4f5313b..0bbfbf5 100644 (file)
--- a/scheme.4th
+++ b/scheme.4th
@@ -7,38 +7,68 @@ 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
 
-: store-parse-idx
-    parse-idx @ dummy-parse-idx !  ;
 
-: restore-parse-idx
-    dummy-parse-idx @ parse-idx !  ;
+create parse-idx-stack 10 allot 
+variable parse-idx-sp
+parse-idx-stack parse-idx-sp !
 
-variable parse-str
+: 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 +! ;
+
+: dec-parse-idx
+    1 parse-idx -! ;
 
 : 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?
@@ -50,7 +80,7 @@ variable parse-str
     begin
         whitespace?
     while
-            1 parse-idx +!
+        inc-parse-idx
     repeat
 ;
 
@@ -68,18 +98,18 @@ variable parse-str
         exit
     then
 
-    store-parse-idx
-    1 parse-idx +!
+    push-parse-idx
+    inc-parse-idx
 
     begin digit? while
-        1 parse-idx +!
+        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
 ;
@@ -87,26 +117,72 @@ variable parse-str
 : boolean? ( -- bool )
     nextchar [char] # <> if false exit then
 
-    1 parse-idx +!
+    push-parse-idx
+    inc-parse-idx
 
     nextchar [char] t <>
     nextchar [char] f <>
-    and if 1 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
 
-    1 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
+
+    push-parse-idx
+    inc-parse-idx
+
+    nextchar [char] \ <> if pop-parse-idx false exit then
+
+    inc-parse-idx
+
+    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
+
+    pop-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
@@ -115,7 +191,7 @@ variable parse-str
 ;
 
 : readbool ( -- bool-atom )
-    1 parse-idx +!
+    inc-parse-idx
     
     nextchar [char] f = if
         false
@@ -123,10 +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
@@ -141,6 +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
@@ -166,6 +249,7 @@ variable parse-str
 \ ---- Print ----
 
 : printnum ( numobj -- ) drop . ;
+
 : printbool ( numobj -- )
     drop if
         ." #t"
@@ -175,43 +259,24 @@ variable parse-str
 ;
 
 : print ( obj -- )
-    ." ;"
+    ." ; "
     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 cr 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
 
-    begin
-        cr bold fg green ." => " reset-term
-        getline
-
-        eof? if
-            bold fg blue ." Moriturus te saluto." reset-term
-            exit
-        then
+    empty-parse-str
 
-        repl-buffer @ 0> if
-            0 parse-idx !
-            read
-            eval
-            fg cyan print reset-term
-        then
+    begin
+        cr bold fg green ." > " reset-term
+        read
+        eval
+        fg cyan print reset-term
     again
 ;