X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme.4th;h=8581893525ce82400121347baa0aa7eecd7ad9d6;hb=fb1e77539ea2eea41e87cb50743a2e4df8e8dac5;hp=915edbad79021f817a5d24dffdd8fa6fe89136c3;hpb=95c071f1ce6af0571791b2e8b885780182982dff;p=scheme.forth.jl.git

diff --git a/scheme.4th b/scheme.4th
index 915edba..8581893 100644
--- a/scheme.4th
+++ b/scheme.4th
@@ -4,15 +4,21 @@ scheme definitions
 include term-colours.4th
 include defer-is.4th
 
+\ ------ Types ------
+
 0 constant number-type
 1 constant boolean-type
 2 constant character-type
-3 constant nil-type
-4 constant pair-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 = ;
 
-100 constant N
+\ ------ Cons cell memory ------ {{{
+
+1000 constant N
 create car-cells N allot
 create car-type-cells N allot
 create cdr-cells N allot
@@ -32,7 +38,211 @@ variable nextfree
     1 nextfree +!
 ;
 
-\ ---- Read ----
+: 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 + @
+;
+
+: set-car! ( obj pair-obj -- )
+    drop dup
+    rot swap  car-type-cells + !
+    car-cells + !
+;
+
+: set-cdr! ( obj pair-obj -- )
+    drop dup
+    rot swap  cdr-type-cells + !
+    cdr-cells + !
+;
+
+: caar car car ;
+: cadr cdr car ;
+: cdar car cdr ;
+: cddr cdr cdr ;
+
+: nil 0 nil-type ;
+: nil? nil-type istype? ;
+
+: objvar create nil swap , , ;
+
+: 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+ @ ; 
+
+: objeq? ( obj obj -- bool )
+    rot = -rot = and ;
+
+\ }}}
+
+\ ---- Pre-defined symbols ---- {{{
+
+objvar symbol-table
+
+: (create-symbol) ( addr n -- symbol-obj )
+    dup 0= if
+        2drop nil
+    else
+        2dup drop @ character-type 2swap
+        swap 1+ swap 1-
+        recurse
+
+        cons
+    then
+;
+
+: create-symbol ( -- )
+    bl word
+    count
+
+    (create-symbol)
+    drop symbol-type
+
+    2dup
+
+    symbol-table fetchobj
+    cons
+    symbol-table setobj
+
+    create swap , ,
+    does> dup @ swap 1+ @
+;
+
+create-symbol quote     quote-symbol
+create-symbol define    define-symbol
+create-symbol set!      set!-symbol
+create-symbol ok        ok-symbol
+
+\ }}}
+
+\ ---- Environments ---- {{{
+
+: enclosing-env ( env -- env )
+    cdr ;
+
+: first-frame ( env -- frame )
+    car ;
+
+: make-frame ( vars vals -- frame )
+    cons ;
+
+: frame-vars ( frame -- vars )
+    car ;
+
+: frame-vals ( frame -- vals )
+    cdr ;
+
+: add-binding ( var val frame -- )
+    2swap 2over frame-vals cons
+    2over set-cdr!
+    2swap 2over frame-vars cons
+    2swap set-car!
+;
+
+: extend-env ( vars vals env -- env )
+    >R >R
+    make-frame
+    R> R>
+    cons
+;
+
+objvar vars
+objvar vals
+
+: get-vars-vals-frame ( var frame -- bool )
+    2dup frame-vars vars setobj
+    frame-vals vals setobj
+
+    begin
+        vars fetchobj nil objeq? false =
+    while
+        2dup vars fetchobj car objeq? if
+            2drop true
+            exit
+        then
+
+        vars fetchobj cdr vars setobj
+        vals fetchobj cdr vals setobj
+    repeat
+
+    2drop false
+;
+
+: get-vars-vals ( var env -- vars? vals? bool )
+
+    begin
+        2dup nil objeq? false =
+    while
+        2over 2over first-frame
+        get-vars-vals-frame if
+            2drop 2drop
+            vars fetchobj vals fetchobj true
+            exit
+        then
+
+        enclosing-env
+    repeat
+
+    2drop 2drop
+    false
+;
+
+hide vars
+hide vals
+
+: lookup-var ( var env -- val )
+    get-vars-vals if
+        2swap 2drop car
+    else
+        bold fg red ." Tried to read unbound variable." reset-term cr abort
+    then
+;
+
+: set-var ( var val env -- )
+    >R >R 2swap R> R> ( val var env )
+    get-vars-vals if
+        2swap 2drop ( val vals )
+        set-car!
+    else
+        bold fg red ." Tried to set unbound variable." reset-term cr abort
+    then
+;
+
+objvar env
+
+: define-var ( var val env -- )
+    env setobj 
+
+    2over env fetchobj ( var val var env )
+    get-vars-vals if
+        2swap 2drop ( var val vals )
+        set-car!
+        2drop
+    else
+        env fetchobj
+        first-frame ( var val frame )
+        add-binding
+    then
+;
+
+hide env
+
+objvar global-env
+nil nil nil extend-env
+global-env setobj
+
+\ }}}
+
+\ ---- Read ---- {{{
 
 variable parse-idx
 variable stored-parse-idx
@@ -198,6 +408,8 @@ parse-idx-stack parse-idx-sp !
 : pair? ( -- bool )
     nextchar [char] ( = ;
 
+: string? ( -- bool )
+    nextchar [char] " = ;
 
 : readnum ( -- num-atom )
     minus? dup if
@@ -243,10 +455,105 @@ parse-idx-stack parse-idx-sp !
     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
+            2drop 2drop true exit
+        else
+            2drop 2drop false exit
+        then
+    else
+        nil? -rot 2drop
+        if
+            2drop 2drop false exit
+        then
+    then
+
+    2over 2over
+
+    \ Neither nil
+    car drop -rot car drop = if
+            cdr 2swap cdr recurse
+        else
+            2drop 2drop false
+    then
+;
+
+: charlist>symbol ( charlist -- symbol-obj )
+
+    symbol-table fetchobj
+
+    begin
+        nil? false =
+    while
+        2over 2over
+        car drop pair-type
+        charlist-equiv if
+            2swap 2drop
+            car
+            exit
+        else
+            cdr
+        then
+    repeat
+
+    2drop
+    drop symbol-type 2dup
+    symbol-table fetchobj cons
+    symbol-table setobj
+;
+
 defer read
 
-: readpair ( -- obj )
-    inc-parse-idx
+: readpair ( -- pairobj )
     eatspaces
 
     \ Empty lists
@@ -259,7 +566,9 @@ defer read
             reset-term abort
         then
 
-        nil-type exit
+        dec-parse-idx
+
+        0 nil-type exit
     then
 
     \ Read first pair element
@@ -277,16 +586,17 @@ defer read
         then
 
         eatspaces read
-
     else
         recurse
     then
 
+    eatspaces
+
     cons
 ;
 
 \ Parse a scheme expression
-: (read) ( -- obj )
+:noname ( -- obj )
 
     eatspaces
 
@@ -305,45 +615,173 @@ defer read
         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
+
     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
 
+    nextchar [char] ' = if
+        inc-parse-idx
+        quote-symbol recurse nil cons cons 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
-;
+    \ Anything else is parsed as a symbol
+    readsymbol charlist>symbol
+
+; is read
 
-' (read) is read
+\ }}}
 
-\ ---- Eval ----
+\ ---- Eval ---- {{{
 
 : self-evaluating? ( obj -- obj bool )
-    number-type istype? if true exit then
     boolean-type istype? if true exit then
+    number-type istype? if true exit then
     character-type istype? if true exit then
+    string-type istype? if true exit then
     nil-type istype? if true exit then
-    false ;
 
-: eval
+    false
+;
+
+: tagged-list? ( obj tag-obj -- obj bool )
+    2over 
+    pair-type istype? false = if
+        2drop 2drop false
+    else
+        car objeq?
+    then ;
+
+: quote? ( obj -- obj bool )
+    quote-symbol tagged-list?  ;
+
+: quote-body ( quote-obj -- quote-body-obj )
+    cadr ;
+
+: variable? ( obj -- obj bool )
+    symbol-type istype? ;
+
+: definition? ( obj -- obj bool )
+    define-symbol tagged-list? ;
+
+: definition-var ( obj -- var )
+    cdr car ;
+
+: definition-val ( obj -- val )
+    cdr cdr car ;
+
+: assignment? ( obj -- obj bool )
+    set!-symbol tagged-list? ;
+
+: assignment-var ( obj -- var )
+    cdr car ;
+    
+: assignment-val ( obj -- val )
+    cdr cdr car ;
+
+defer eval
+
+: eval-definition ( obj env -- res )
+    2swap 
+    2over 2over ( env obj env obj )
+    definition-val 2swap ( env obj valexp env )
+    eval  ( env obj val )
+    
+    2swap definition-var 2swap ( env var val )
+
+    >R >R 2swap R> R> 2swap ( var val env )
+    define-var
+
+    ok-symbol
+;
+    
+: eval-assignment ( obj env -- res )
+    2swap 
+    2over 2over ( env obj env obj )
+    assignment-val 2swap ( env obj valexp env )
+    eval  ( env obj val )
+    
+    2swap assignment-var 2swap ( env var val )
+
+    >R >R 2swap R> R> 2swap ( var val env )
+    set-var
+
+    ok-symbol
+;
+
+:noname ( obj env -- result )
+    2swap
+
     self-evaluating? if
+        2swap 2drop
+        exit
+    then
+
+    quote? if
+        quote-body
+        2swap 2drop
+        exit
+    then
+
+    variable? if
+        2swap lookup-var
+        exit
+    then
+
+    definition? if
+        2swap eval-definition
+        exit
+    then
+
+    assignment? if
+        2swap eval-assignment
         exit
     then
 
     bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
     abort
-;
+; is eval
 
-\ ---- Print ----
+\ }}}
 
-: printnum ( numobj -- ) drop . ;
+\ ---- Print ---- {{{
+
+: printnum ( numobj -- ) drop 0 .R ;
 
 : printbool ( numobj -- )
     drop if
@@ -364,16 +802,58 @@ defer read
     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 -- )
-    drop ." ()" ;
+    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
+;
 
-: print ( obj -- )
-    ." ; "
+: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 ----
 
@@ -386,9 +866,11 @@ defer read
     begin
         cr bold fg green ." > " reset-term
         read
-        eval
-        fg cyan print reset-term
+        global-env fetchobj eval
+        fg cyan ." ; " print reset-term
     again
 ;
 
 forth definitions
+
+\ vim:fdm=marker