X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme.4th;h=10e4f2698ea27897d742f8b07899ca4841533d7c;hb=0709203cb8054ba71819df58791725afe2587afe;hp=524f3a1fccf4f31c3ffcb63fc7a81bed226c7fec;hpb=35aac989c77e879267931748dca2ca1da01d4e08;p=scheme.forth.jl.git

diff --git a/scheme.4th b/scheme.4th
index 524f3a1..10e4f26 100644
--- a/scheme.4th
+++ b/scheme.4th
@@ -1,16 +1,70 @@
-\ Scheme interpreter
-
 vocabulary scheme
 scheme definitions
 
 include term-colours.4th
+include defer-is.4th
+
+\ ------ Types ------
 
 0 constant number-type
 1 constant boolean-type
 2 constant character-type
-: istype? ( obj -- obj b )
+3 constant string-type
+4 constant nil-type
+5 constant pair-type
+6 constant symbol-type
+: istype? ( obj type -- obj bool )
     over = ;
 
+\ ------ Memory ------
+
+100 constant N
+create car-cells N allot
+create car-type-cells N allot
+create cdr-cells N allot
+create cdr-type-cells N allot
+
+variable nextfree
+0 nextfree !
+
+: cons ( car-obj cdr-obj -- pair-obj )
+    cdr-type-cells nextfree @ + !
+    cdr-cells nextfree @ + !
+    car-type-cells nextfree @ + !
+    car-cells nextfree @ + !
+
+    nextfree @ pair-type
+
+    1 nextfree +!
+;
+
+: car ( pair-obj -- car-obj )
+    drop
+    dup car-cells + @ swap
+    car-type-cells + @
+;
+
+: cdr ( pair-obj -- car-obj )
+    drop
+    dup cdr-cells + @ swap
+    cdr-type-cells + @
+;
+
+: nil 0 nil-type ;
+: nil? nil-type istype? ;
+
+: objvar create 0 , 0 , ;
+
+: value@ ( objvar -- val ) @ ;
+: type@ ( objvar -- type ) 1+ @ ;
+: value! ( newval objvar -- ) ! ;
+: type! ( newtype objvar -- ) 1+ ! ;
+: setobj ( newobj objvar -- ) dup rot swap 1+ ! ! ; 
+: fetchobj ( objvar -- obj ) dup @ swap 1+ @ ; 
+
+objvar symbol-table
+nil symbol-table setobj
+
 \ ---- Read ----
 
 variable parse-idx
@@ -18,12 +72,33 @@ 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 +109,8 @@ 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 +118,10 @@ variable parse-str-span
 
 : whitespace? ( -- bool )
     nextchar BL = 
-    nextchar '\n' = or
-;
+    nextchar '\n' = or ;
+
+: eof? ( -- bool )
+    nextchar 4 = ;
 
 : delim? ( -- bool )
     whitespace?
@@ -82,18 +151,18 @@ 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 +170,92 @@ 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 pop-parse-idx true exit then
+    S" space" str-equiv? if pop-parse-idx true exit then
+    S" tab" str-equiv? if pop-parse-idx true exit then
+
+    charavailable? false = if pop-parse-idx false exit then
+
+    pop-parse-idx true
+;
+
+: pair? ( -- bool )
+    nextchar [char] ( = ;
+
+: string? ( -- bool )
+    nextchar [char] " = ;
+
+: initial? ( -- bool )
+    nextchar [char] A >= nextchar [char] Z <= and if true exit then
+    nextchar [char] a >= nextchar [char] z <= and if true exit then
+    nextchar [char] * = if true exit then
+    nextchar [char] / = if true exit then
+    nextchar [char] > = if true exit then
+    nextchar [char] < = if true exit then
+    nextchar [char] = = if true exit then
+    nextchar [char] ? = if true exit then
+    nextchar [char] ! = if true exit then
+    false
+;
 
-    restore-parse-idx true
+: symbol? ( -- bool )
+    initial? if true exit then
+    nextchar [char] + =
+    nextchar [char] - = or if
+        inc-parse-idx
+        delim? if dec-parse-idx true exit then
+        dec-parse-idx
+    then
+    false
 ;
 
 : readnum ( -- num-atom )
@@ -153,11 +284,156 @@ 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 7 parse-idx +! '\n' character-type exit then
+    S" space" str-equiv? if 5 parse-idx +! bl character-type exit then
+    S" tab" str-equiv? if 3 parse-idx +! 9 character-type exit then
+
+    nextchar character-type
+
+    inc-parse-idx
+;
+
+: readstring ( -- charlist )
+    nextchar [char] " = if
+        inc-parse-idx
+
+        delim? false = if
+            bold fg red
+            ." No delimiter following right double quote. Aborting." cr
+            reset-term abort
+        then
+
+        dec-parse-idx
+
+        0 nil-type exit
+    then
+
+    nextchar [char] \ = if
+        inc-parse-idx
+        nextchar case
+            [char] n of '\n' endof
+            [char] " of [char] " endof
+            [char] \
+        endcase
+    else
+        nextchar
+    then
+    inc-parse-idx character-type
+
+    recurse
+
+    cons
+;
+
+: readsymbol ( -- charlist )
+    delim? if nil exit then
+
+    nextchar inc-parse-idx character-type
+
+    recurse
+
+    cons
+;
+
+: charlist-equiv ( charlist charlist -- bool )
+
+    2over 2over
+
+    \ One or both nil
+    nil? -rot 2drop
+    if
+        nil? -rot 2drop
+        if
+            true exit
+        else
+            false exit
+        then
+    else
+        nil? -rot 2drop
+        if
+            false exit
+        then
+    then
+
+    2over 2over
+
+    \ Neither nil
+    car 2swap car rot = -rot = and if
+            cdr 2swap cdr recurse
+        else
+            2drop 2drop false
+    then
+;
+
+: (symbol-in-table?) ( charlist symbol-table -- charlist symbol-obj )
+
+    begin
+        nil? false =
+    while
+        2over 2over
+        car
+        charlist-equiv if
+    repeat
+;
+
+: symbol-in-table? ( charlist -- charlist bool )
+    symbol-table (symbol-in-table?) ;
+
+defer read
+
+: readpair ( -- obj )
+    eatspaces
+
+    \ Empty lists
+    nextchar [char] ) = if
+        inc-parse-idx
+
+        delim? false = if
+            bold fg red
+            ." No delimiter following right paren. Aborting." cr
+            reset-term abort
+        then
+
+        dec-parse-idx
+
+        0 nil-type exit
+    then
+
+    \ Read first pair element
+    read
+
+    \ Pairs
+    eatspaces
+    nextchar [char] . = if
+        inc-parse-idx
+
+        delim? false = if
+            bold fg red
+            ." No delimiter following '.'. Aborting." cr
+            reset-term abort
+        then
+
+        eatspaces read
+    else
+        recurse
+    then
+
+    eatspaces
+
+    cons
+;
+
 \ Parse a scheme expression
-: read ( -- obj )
+:noname ( -- obj )
 
     eatspaces
 
@@ -171,18 +447,71 @@ variable parse-str-span
         exit
     then
 
+    character? if
+        readchar
+        exit
+    then
+
+    string? if
+        inc-parse-idx
+        readstring
+        drop string-type
+
+        nextchar [char] " <> if
+            bold red ." Missing closing double-quote." reset-term cr
+            abort
+        then
+
+        inc-parse-idx
+        exit
+    then
+
+    symbol? if
+        readsymbol
+        drop symbol-type
+        2dup
+        symbol-table fetch
+        cons
+        symbol-table set
+        exit
+    then
+
+    pair? if
+        inc-parse-idx
+
+        eatspaces
+
+        readpair
+
+        eatspaces
+
+        nextchar [char] ) <> if
+            bold red ." Missing closing paren." reset-term cr
+            abort
+        then
+
+        inc-parse-idx
+
+        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
     abort
-;
+
+; is read
 
 \ ---- Eval ----
 
 : self-evaluating? ( obj -- obj bool )
-    number-type istype? if true exit then
-    boolean-type istype? if true exit then
-    false ;
+    true \ everything self-evaluating for now
+;
 
 : eval
     self-evaluating? if
@@ -195,7 +524,7 @@ variable parse-str-span
 
 \ ---- Print ----
 
-: printnum ( numobj -- ) drop . ;
+: printnum ( numobj -- ) drop 0 .R ;
 
 : printbool ( numobj -- )
     drop if
@@ -205,23 +534,81 @@ variable parse-str-span
     then
 ;
 
-: print ( obj -- )
-    ." ; "
-    number-type istype? if ." => " printnum exit then
-    boolean-type istype? if ." => " printbool exit then
+: printchar ( charobj -- )
+    drop
+    case
+        9 of ." #\tab" endof
+        bl of ." #\space" endof
+        '\n' of ." #\newline" endof
+        
+        dup ." #\" emit
+    endcase
+;
+
+: (printstring) ( stringobj -- )
+    nil-type istype? if 2drop exit then
+
+    2dup car drop dup
+    case
+        '\n' of ." \n" drop endof
+        [char] \ of ." \\" drop endof
+        [char] " of [char] \ emit [char] " emit drop endof
+        emit
+    endcase
+
+    cdr recurse
+;
+: printstring ( stringobj -- )
+    [char] " emit
+    (printstring)
+    [char] " emit ;
+
+: printsymbol ( symbolobj -- )
+    nil-type istype? if 2drop exit then
+
+    2dup car drop emit
+    cdr recurse
+;
+
+: printnil ( nilobj -- )
+    2drop ." ()" ;
+
+defer print
+: printpair ( pairobj -- )
+    2dup
+    car print
+    cdr
+    nil-type istype? if 2drop exit then
+    pair-type istype? if space recurse exit then
+    ."  . " print
 ;
 
+:noname ( obj -- )
+    number-type istype? if printnum exit then
+    boolean-type istype? if printbool exit then
+    character-type istype? if printchar exit then
+    string-type istype? if printstring exit then
+    symbol-type istype? if printsymbol exit then
+    nil-type istype? if printnil exit then
+    pair-type istype? if ." (" printpair ." )" exit then
+
+    bold fg red ." Error printing expression - unrecognized type. Aborting" reset-term cr
+    abort
+; is print
+
 \ ---- REPL ----
 
 : repl
     cr ." Welcome to scheme.forth.jl!" cr
        ." Use Ctrl-D to exit." cr
 
+    empty-parse-str
+
     begin
         cr bold fg green ." > " reset-term
         read
         eval
-        fg cyan print reset-term
+        fg cyan ." ; " print reset-term
     again
 ;