X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme.4th;h=ea02cd513b424fd72efede52139568e87c758204;hb=26a971100b29dee243a42096d52d69ca518905ea;hp=08a72b5380f53be0a757e46b54b2f3a6f2e41abe;hpb=7f58e8a0232663cd99ea18fd249d1e590ceb6fff;p=scheme.forth.jl.git

diff --git a/scheme.4th b/scheme.4th
index 08a72b5..ea02cd5 100644
--- a/scheme.4th
+++ b/scheme.4th
@@ -18,6 +18,23 @@ 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 +! ;
@@ -38,12 +55,6 @@ 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 @ > ;
 
@@ -86,18 +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
 ;
@@ -105,30 +116,60 @@ 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
+
+    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 )
@@ -162,6 +203,19 @@ variable parse-str-span
     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 )
 
@@ -177,6 +231,11 @@ variable parse-str-span
         exit
     then
 
+    character? if
+        readchar
+        exit
+    then
+
     eof? if
         bold fg blue ." Moriturus te saluto." reset-term ."  ok" cr
         quit
@@ -216,10 +275,20 @@ variable parse-str-span
     then
 ;
 
+: printchar ( charobj -- )
+    drop
+    case
+        9 of ." #\tab" endof
+        bl of ." #\space" endof
+        '\n' of ." #\newline" endof
+    endcase
+;
+
 : print ( obj -- )
     ." ; "
     number-type istype? if printnum exit then
     boolean-type istype? if printbool exit then
+    character-type istype? if printchar exit then
 ;
 
 \ ---- REPL ----