X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme.4th;h=a4e2d070ed72794a6348f502d1f75f12c813631c;hb=05e51ddd2d399b1a5c512aa355618a7d044e393f;hp=524f3a1fccf4f31c3ffcb63fc7a81bed226c7fec;hpb=35aac989c77e879267931748dca2ca1da01d4e08;p=scheme.forth.jl.git

diff --git a/scheme.4th b/scheme.4th
index 524f3a1..a4e2d07 100644
--- a/scheme.4th
+++ b/scheme.4th
@@ -18,12 +18,33 @@ 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
-    1 parse-str-span +!
-    '\n' parse-str parse-str-span @ + ! ;
+    '\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
+    parse-str 160 expect cr
     span @ parse-str-span !
     append-newline
     0 parse-idx ! ;
@@ -34,16 +55,8 @@ variable parse-str-span
 : dec-parse-idx
     1 parse-idx -! ;
 
-: store-parse-idx
-    parse-idx @ stored-parse-idx !  ;
-
-: restore-parse-idx
-    stored-parse-idx @ parse-idx !  ;
-
-
 : charavailable? ( -- bool )
-    parse-str-span @ parse-idx @ >
-;
+    parse-str-span @ parse-idx @ > ;
 
 : nextchar ( -- char )
     charavailable? false = if getline then
@@ -51,8 +64,10 @@ variable parse-str-span
 
 : whitespace? ( -- bool )
     nextchar BL = 
-    nextchar '\n' = or
-;
+    nextchar '\n' = or ;
+
+: eof? ( -- bool )
+    nextchar 4 = ;
 
 : delim? ( -- bool )
     whitespace?
@@ -82,18 +97,18 @@ variable parse-str-span
         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
 ;
@@ -101,30 +116,62 @@ variable parse-str-span
 : 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
 
-    restore-parse-idx
-    true
+    inc-parse-idx
+    delim? if
+        pop-parse-idx
+        true
+    else
+        pop-parse-idx
+        false
+    then
+;
+
+: str-equiv? ( str -- bool )
+
+    push-parse-idx
+
+    true -rot
+
+    swap dup rot + swap
+
+    do
+        i @ nextchar <> if
+            drop false
+            leave
+        then
+
+        inc-parse-idx
+    loop
+
+    delim? false = 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 )
@@ -153,9 +200,24 @@ variable parse-str-span
         true
     then
 
+    inc-parse-idx
+
     boolean-type
 ;
 
+: readchar ( -- char-atom )
+    inc-parse-idx
+    inc-parse-idx
+
+    S" newline" str-equiv? if '\n' character-type exit then
+    S" space" str-equiv? if bl character-type exit then
+    S" tab" str-equiv? if 9 character-type exit then
+
+    nextchar character-type
+
+    inc-parse-idx
+;
+
 \ Parse a scheme expression
 : read ( -- obj )
 
@@ -171,6 +233,16 @@ variable parse-str-span
         exit
     then
 
+    character? if
+        readchar
+        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
@@ -182,6 +254,7 @@ variable parse-str-span
 : 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
     false ;
 
 : eval
@@ -205,10 +278,24 @@ variable parse-str-span
     then
 ;
 
+: printchar ( charobj -- )
+    drop
+    case
+        9 of ." #\tab" endof
+        bl of ." #\space" endof
+        '\n' of ." #\newline" endof
+        
+        ." #\" emit
+    endcase
+
+    trace
+;
+
 : 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
+    character-type istype? if printchar exit then
 ;
 
 \ ---- REPL ----
@@ -217,6 +304,8 @@ variable parse-str-span
     cr ." Welcome to scheme.forth.jl!" cr
        ." Use Ctrl-D to exit." cr
 
+    empty-parse-str
+
     begin
         cr bold fg green ." > " reset-term
         read