X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme.4th;h=08b4bcd070b0cc912eb283b72479a7da33f9a8db;hb=4d9d90cad9c4280d93d6bf67f2083ef9d3c8235f;hp=4dee70f16a352f0bf8f6ab483facb697a7db141d;hpb=b2a917e726a54a7cc3b21b8559cd166d3c2100f7;p=scheme.forth.jl.git

diff --git a/scheme.4th b/scheme.4th
index 4dee70f..08b4bcd 100644
--- a/scheme.4th
+++ b/scheme.4th
@@ -3,30 +3,73 @@ scheme definitions
 
 include term-colours.4th
 include defer-is.4th
+include float.4th
+
+include debugging.4th
+
+defer read
+defer eval
+defer print
+
+defer collect-garbage
 
 \ ------ Types ------
 
-0 constant number-type
-1 constant boolean-type
-2 constant character-type
-3 constant string-type
-4 constant nil-type
-5 constant pair-type
-6 constant symbol-type
+variable nexttype
+0 nexttype !
+: make-type
+    create nexttype @ ,
+    1 nexttype +!
+    does> @ ;
+
+make-type fixnum-type
+make-type realnum-type
+make-type boolean-type
+make-type character-type
+make-type string-type
+make-type nil-type
+make-type pair-type
+make-type symbol-type
+make-type primitive-proc-type
+make-type compound-proc-type
+make-type fileport-type
 : istype? ( obj type -- obj bool )
     over = ;
 
-\ ------ Cons cell memory ------ {{{
+\ ------ List-structured memory ------ {{{
+
+10000 constant scheme-memsize
 
-1000 constant N
-create car-cells N allot
-create car-type-cells N allot
-create cdr-cells N allot
-create cdr-type-cells N allot
+create car-cells scheme-memsize allot
+create car-type-cells scheme-memsize allot
+create cdr-cells scheme-memsize allot
+create cdr-type-cells scheme-memsize allot
 
+create nextfrees scheme-memsize allot
+:noname
+    scheme-memsize 0 do
+        i 1+ nextfrees i + !
+    loop
+; execute
+        
 variable nextfree
 0 nextfree !
 
+: inc-nextfree
+    nextfrees nextfree @ + @
+    nextfree !
+
+    nextfree @ scheme-memsize >= if
+        collect-garbage
+    then
+
+    nextfree @ scheme-memsize >= if
+        fg red bold
+        ." Out of memory! Aborting."
+        reset-term abort
+    then
+;
+
 : cons ( car-obj cdr-obj -- pair-obj )
     cdr-type-cells nextfree @ + !
     cdr-cells nextfree @ + !
@@ -34,8 +77,7 @@ variable nextfree
     car-cells nextfree @ + !
 
     nextfree @ pair-type
-
-    1 nextfree +!
+    inc-nextfree
 ;
 
 : car ( pair-obj -- car-obj )
@@ -76,19 +118,124 @@ variable nextfree
 : type@ ( objvar -- type ) 1+ @ ;
 : value! ( newval objvar -- ) ! ;
 : type! ( newtype objvar -- ) 1+ ! ;
-: setobj ( newobj objvar -- ) dup rot swap 1+ ! ! ; 
-: fetchobj ( objvar -- obj ) dup @ swap 1+ @ ; 
+: obj! ( newobj objvar -- ) dup rot swap 1+ ! ! ; 
+: obj@ ( objvar -- obj ) dup @ swap 1+ @ ; 
 
 : objeq? ( obj obj -- bool )
     rot = -rot = and ;
 
+: 2rot ( a1 a2 b1 b2 c1 c2 -- b1 b2 c1 c2 a1 a2 )
+    >R >R ( a1 a2 b1 b2 )
+    2swap ( b1 b2 a1 a2 )
+    R> R> ( b1 b2 a1 a2 c1 c2 )
+    2swap
+;
+
+: -2rot ( a1 a2 b1 b2 c1 c2 -- c1 c2 a1 a2 b1 b2 )
+    2swap ( a1 a2 c1 c2 b1 b2 )
+    >R >R ( a1 a2 c1 c2 )
+    2swap ( c1 c2 a1 a2 )
+    R> R>
+;
+
+\ }}}
+
+\ ---- Port I/O ----  {{{
+
+: fileport>fid ( fileport -- fid )
+    drop ;
+
+: fid>fileport ( fid -- fileport )
+    fileport-type ;
+
+: open-input-file ( addr n -- fileport )
+    r/o open-file drop fid>fileport
+;
+
+: close-port ( fileport -- )
+    fileport>fid close-file drop
+;
+
+objvar console-i/o-port
+0 fileport-type console-i/o-port obj!
+
+objvar current-input-port
+console-i/o-port obj@ current-input-port obj!
+
+: read-port ( fileport -- obj )
+    current-input-port obj!
+    read ;
+
+: read-console ( -- obj )
+    console-i/o-port obj@ read-port ;
+
 \ }}}
 
 \ ---- Pre-defined symbols ---- {{{
 
 objvar symbol-table
 
-: (create-symbol) ( addr n -- symbol-obj )
+: duplicate-charlist ( charlist -- copy )
+    2dup nil objeq? false = if
+        2dup car 2swap cdr recurse cons
+    then ;
+
+: 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 obj@
+
+    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 obj@ cons
+    symbol-table obj!
+;
+
+
+: cstr>charlist ( addr n -- symbol-obj )
     dup 0= if
         2drop nil
     else
@@ -104,14 +251,14 @@ objvar symbol-table
     bl word
     count
 
-    (create-symbol)
+    cstr>charlist
     drop symbol-type
 
     2dup
 
-    symbol-table fetchobj
+    symbol-table obj@
     cons
-    symbol-table setobj
+    symbol-table obj!
 
     create swap , ,
     does> dup @ swap 1+ @
@@ -121,6 +268,10 @@ create-symbol quote     quote-symbol
 create-symbol define    define-symbol
 create-symbol set!      set!-symbol
 create-symbol ok        ok-symbol
+create-symbol if        if-symbol
+create-symbol lambda    lambda-symbol
+create-symbol λ         λ-symbol
+create-symbol begin     begin-symbol
 
 \ }}}
 
@@ -143,9 +294,9 @@ create-symbol ok        ok-symbol
 
 : add-binding ( var val frame -- )
     2swap 2over frame-vals cons
-    2over set-car!
+    2over set-cdr!
     2swap 2over frame-vars cons
-    swap set-cdr!
+    2swap set-car!
 ;
 
 : extend-env ( vars vals env -- env )
@@ -159,19 +310,19 @@ objvar vars
 objvar vals
 
 : get-vars-vals-frame ( var frame -- bool )
-    2dup frame-vars vars setobj
-    frame-vals vals setobj
+    2dup frame-vars vars obj!
+    frame-vals vals obj!
 
     begin
-        vars fetchobj nil objeq? false =
+        vars obj@ nil objeq? false =
     while
-        2dup vars fetchobj car objeq? if
+        2dup vars obj@ car objeq? if
             2drop true
             exit
         then
 
-        vars fetchobj cdr vars setobj
-        vals fetchobj cdr vals setobj
+        vars obj@ cdr vars obj!
+        vals obj@ cdr vals obj!
     repeat
 
     2drop false
@@ -185,7 +336,7 @@ objvar vals
         2over 2over first-frame
         get-vars-vals-frame if
             2drop 2drop
-            vars fetchobj vals fetchobj true
+            vars obj@ vals obj@ true
             exit
         then
 
@@ -203,7 +354,7 @@ hide vals
     get-vars-vals if
         2swap 2drop car
     else
-        bold fg red ." Tried to read unbound variable." reset-term abort
+        bold fg red ." Tried to read unbound variable." reset-term cr abort
     then
 ;
 
@@ -213,22 +364,22 @@ hide vals
         2swap 2drop ( val vals )
         set-car!
     else
-        bold fg red ." Tried to set unbound variable." reset-term abort
+        bold fg red ." Tried to set unbound variable." reset-term cr abort
     then
 ;
 
 objvar env
 
 : define-var ( var val env -- )
-    env setobj 
+    env obj! 
 
-    2over env fetchobj ( var val var env )
+    2over env obj@ ( var val var env )
     get-vars-vals if
         2swap 2drop ( var val vals )
         set-car!
         2drop
     else
-        env fetchobj
+        env obj@
         first-frame ( var val frame )
         add-binding
     then
@@ -238,7 +389,7 @@ hide env
 
 objvar global-env
 nil nil nil extend-env
-global-env setobj
+global-env obj!
 
 \ }}}
 
@@ -270,13 +421,24 @@ parse-idx-stack parse-idx-sp !
     '\n' parse-str parse-str-span @ + !
     1 parse-str-span +! ;
 
+: append-eof
+    4 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 !
+    current-input-port obj@ console-i/o-port obj@ objeq? if
+        parse-str 160 expect cr
+        span @ parse-str-span !
+    else
+        parse-str 160 current-input-port obj@ fileport>fid read-line
+        drop swap parse-str-span !
+
+        parse-str-span @ 0= and if append-eof then
+    then
     append-newline
     0 parse-idx ! ;
 
@@ -293,12 +455,16 @@ parse-idx-stack parse-idx-sp !
     charavailable? false = if getline then
     parse-str parse-idx @ + @ ;
 
+: '\t' 9 ;
 : whitespace? ( -- bool )
     nextchar BL = 
-    nextchar '\n' = or ;
+    nextchar '\n' =
+    nextchar '\t' =
+    or or ;
 
+: EOF 4 ; 
 : eof? ( -- bool )
-    nextchar 4 = ;
+    nextchar EOF = ;
 
 : delim? ( -- bool )
     whitespace?
@@ -306,12 +472,27 @@ parse-idx-stack parse-idx-sp !
     nextchar [char] ) = or
 ;
 
+: commentstart? ( -- bool )
+    nextchar [char] ; = ;
+
 : eatspaces
+
+    false \ Indicates whether or not we're eating a comment
+
     begin
-        whitespace?
+        dup whitespace? or commentstart? or
     while
+        dup nextchar '\n' = and if
+            invert \ Stop eating comment
+        else
+            dup false = commentstart? and if   
+                invert \ Begin eating comment
+            then
+        then
+
         inc-parse-idx
     repeat
+    drop
 ;
 
 : digit? ( -- bool )
@@ -322,10 +503,23 @@ parse-idx-stack parse-idx-sp !
 : minus? ( -- bool )
     nextchar [char] - = ;
 
-: number? ( -- bool )
-    digit? minus? or false = if
-        false
-        exit
+: plus? ( -- bool )
+    nextchar [char] + = ;
+
+: fixnum? ( -- bool )
+    minus? plus? or if
+        inc-parse-idx
+
+        delim? if
+            dec-parse-idx
+            false exit
+        else
+            dec-parse-idx
+        then
+    else
+        digit? false = if
+            false exit
+        then
     then
 
     push-parse-idx
@@ -335,13 +529,52 @@ parse-idx-stack parse-idx-sp !
         inc-parse-idx
     repeat
 
-    delim? if
-        pop-parse-idx
-        true
-    else
-        pop-parse-idx
-        false
+    delim? pop-parse-idx
+;
+
+: realnum? ( -- bool )
+    push-parse-idx
+
+    minus? plus? or if
+        inc-parse-idx
+    then
+
+    \ Record starting parse idx:
+    \ Want to detect whether any characters (following +/-) were eaten.
+    parse-idx @
+
+    begin digit? while
+            inc-parse-idx
+    repeat
+
+    [char] . nextchar = if
+        inc-parse-idx
+        begin digit? while
+                inc-parse-idx
+        repeat
+    then
+
+    [char] e nextchar = [char] E nextchar = or if
+        inc-parse-idx
+
+        minus? plus? or if
+            inc-parse-idx
+        then
+
+        digit? invert if
+            drop pop-parse-idx false exit
+        then
+
+        begin digit? while
+                inc-parse-idx
+        repeat
     then
+
+    \ This is a real number if characters were
+    \ eaten and the next characer is a delimiter.
+    parse-idx @ < delim? and
+
+    pop-parse-idx
 ;
 
 : boolean? ( -- bool )
@@ -411,9 +644,12 @@ parse-idx-stack parse-idx-sp !
 : string? ( -- bool )
     nextchar [char] " = ;
 
-: readnum ( -- num-atom )
-    minus? dup if
+: readfixnum ( -- num-atom )
+    plus? minus? or if
+        minus?
         inc-parse-idx
+    else
+        false
     then
 
     0
@@ -425,10 +661,28 @@ parse-idx-stack parse-idx-sp !
 
     swap if negate then
 
-    number-type
+    fixnum-type
+;
+
+: readrealnum ( -- realnum )
+
+    \ Remember that at this point we're guaranteed to
+    \ have a parsable real on this line.
+
+    parse-str parse-idx @ +
+
+    begin delim? false = while
+            inc-parse-idx
+    repeat
+
+    parse-str parse-idx @ + over -
+
+    float-parse
+
+    realnum-type
 ;
 
-: readbool ( -- bool-atom )
+: readbool ( -- bool-obj )
     inc-parse-idx
     
     nextchar [char] f = if
@@ -442,7 +696,7 @@ parse-idx-stack parse-idx-sp !
     boolean-type
 ;
 
-: readchar ( -- char-atom )
+: readchar ( -- char-obj )
     inc-parse-idx
     inc-parse-idx
 
@@ -497,62 +751,6 @@ parse-idx-stack parse-idx-sp !
     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 ( -- pairobj )
     eatspaces
 
@@ -600,8 +798,13 @@ defer read
 
     eatspaces
 
-    number? if
-        readnum
+    fixnum? if
+        readfixnum
+        exit
+    then
+
+    realnum? if
+        readrealnum
         exit
     then
 
@@ -656,13 +859,20 @@ defer read
     then
 
     eof? if
-        bold fg blue ." Moriturus te saluto." reset-term ."  ok" cr
-        quit
+        EOF character-type
+        inc-parse-idx
+        exit
     then
 
     \ Anything else is parsed as a symbol
     readsymbol charlist>symbol
 
+    \ Replace λ with lambda
+    2dup λ-symbol objeq? if
+        2drop lambda-symbol
+    then
+    
+
 ; is read
 
 \ }}}
@@ -671,7 +881,8 @@ defer read
 
 : self-evaluating? ( obj -- obj bool )
     boolean-type istype? if true exit then
-    number-type istype? if true exit then
+    fixnum-type istype? if true exit then
+    realnum-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
@@ -699,11 +910,23 @@ defer read
 : definition? ( obj -- obj bool )
     define-symbol tagged-list? ;
 
+: make-lambda ( params body -- lambda-exp )
+    lambda-symbol -2rot cons cons ;
+
 : definition-var ( obj -- var )
-    cdr car ;
+    cdr car
+    symbol-type istype? false = if car then
+;
 
 : definition-val ( obj -- val )
-    cdr cdr car ;
+    2dup cdr car symbol-type istype? if
+        2drop
+        cdr cdr car
+    else
+        cdr 2swap cdr cdr
+        make-lambda
+    then
+;
 
 : assignment? ( obj -- obj bool )
     set!-symbol tagged-list? ;
@@ -714,8 +937,6 @@ defer read
 : assignment-val ( obj -- val )
     cdr cdr car ;
 
-defer eval
-
 : eval-definition ( obj env -- res )
     2swap 
     2over 2over ( env obj env obj )
@@ -724,7 +945,7 @@ defer eval
     
     2swap definition-var 2swap ( env var val )
 
-    >R >R 2swap R> R> 2swap ( var val env )
+    2rot ( var val env )
     define-var
 
     ok-symbol
@@ -738,12 +959,146 @@ defer eval
     
     2swap assignment-var 2swap ( env var val )
 
-    >R >R 2swap R> R> 2swap ( var val env )
+    2rot ( var val env )
     set-var
 
     ok-symbol
 ;
 
+: if? ( obj -- obj bool )
+    if-symbol tagged-list? ;
+
+: if-predicate ( ifobj -- pred )
+    cdr car ;
+
+: if-consequent ( ifobj -- conseq )
+    cdr cdr car ;
+
+: if-alternative ( ifobj -- alt|false )
+    cdr cdr cdr
+    2dup nil objeq? if
+        2drop false
+    else
+        car
+    then ;
+
+: false? ( boolobj -- boolean )
+    boolean-type istype? if
+        false boolean-type objeq?
+    else
+        2drop false
+    then
+;
+
+: true? ( boolobj -- bool )
+    false? invert ;
+
+: lambda? ( obj -- obj bool )
+    lambda-symbol tagged-list? ;
+
+: lambda-parameters ( obj -- params )
+    cdr car ;
+
+: lambda-body ( obj -- body )
+    cdr cdr ;
+
+: make-procedure ( params body env -- proc )
+    nil
+    cons cons cons
+    drop compound-proc-type
+;
+
+: begin? ( obj -- obj bool )
+    begin-symbol tagged-list? ;
+
+: begin-actions ( obj -- actions )
+    cdr ;
+
+: eval-sequence ( explist env -- finalexp env )
+    ( Evaluates all bar the final expressions in
+      an an expression list. The final expression
+      is returned to allow for tail optimization. )
+
+    2swap ( env explist )
+
+    \ Abort on empty list
+    2dup nil objeq? if 2swap exit then
+
+    begin
+        2dup cdr ( env explist nextexplist )
+        2dup nil objeq? false =
+    while
+        -2rot car 2over ( nextexplist env exp env )
+        eval
+        2drop \ discard result
+        2swap ( env nextexplist )
+    repeat
+
+    2drop car 2swap ( finalexp env )
+;
+
+: application? ( obj -- obj bool)
+    pair-type istype? ;
+
+: operator ( obj -- operator )
+    car ;
+
+: operands ( obj -- operands )
+    cdr ;
+
+: nooperands? ( operands -- bool )
+    nil objeq? ;
+
+: first-operand ( operands -- operand )
+    car ;
+
+: rest-operands ( operands -- other-operands )
+    cdr ;
+
+: list-of-vals ( args env -- vals )
+    2swap
+
+    2dup nooperands? if
+        2swap 2drop
+    else
+        2over 2over first-operand 2swap eval
+        -2rot rest-operands 2swap recurse
+        cons
+    then
+;
+
+: procedure-params ( proc -- params )
+    drop pair-type car ;
+
+: procedure-body ( proc -- body )
+    drop pair-type cdr car ;
+
+: procedure-env ( proc -- body )
+    drop pair-type cdr cdr car ;
+
+: apply ( proc args )
+        2swap dup case
+            primitive-proc-type of
+                drop execute
+            endof
+
+            compound-proc-type of
+                2dup procedure-body ( args proc body )
+                -2rot 2dup procedure-params ( body args proc params )
+                -2rot procedure-env ( body params args procenv )
+
+                extend-env ( body env )
+
+                eval-sequence
+
+                R> drop ['] eval goto-deferred  \ Tail call optimization
+            endof
+
+            bold fg red ." Object not applicable. Aboring." reset-term cr
+            abort
+        endcase
+;
+
 :noname ( obj env -- result )
     2swap
 
@@ -773,6 +1128,42 @@ defer eval
         exit
     then
 
+    if? if
+        2over 2over
+        if-predicate
+        2swap eval 
+
+        true? if
+            if-consequent
+        else
+            if-alternative
+        then
+
+        2swap
+        ['] eval goto-deferred
+    then
+
+    lambda? if
+        2dup lambda-parameters
+        2swap lambda-body
+        2rot make-procedure
+        exit
+    then
+
+    begin? if
+        \ TODO
+    then
+
+    application? if
+        2over 2over
+        operator 2swap eval
+        -2rot
+        operands 2swap list-of-vals
+
+        apply
+        exit
+    then
+
     bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
     abort
 ; is eval
@@ -781,7 +1172,9 @@ defer eval
 
 \ ---- Print ---- {{{
 
-: printnum ( numobj -- ) drop 0 .R ;
+: printfixnum ( fixnumobj -- ) drop 0 .R ;
+
+: printrealnum ( realnumobj -- ) drop float-print ;
 
 : printbool ( numobj -- )
     drop if
@@ -830,7 +1223,6 @@ defer eval
 : printnil ( nilobj -- )
     2drop ." ()" ;
 
-defer print
 : printpair ( pairobj -- )
     2dup
     car print
@@ -840,14 +1232,23 @@ defer print
     ."  . " print
 ;
 
+: printprim ( primobj -- )
+    2drop ." <primitive procedure>" ;
+
+: printcomp ( primobj -- )
+    2drop ." <compound procedure>" ;
+
 :noname ( obj -- )
-    number-type istype? if printnum exit then
+    fixnum-type istype? if printfixnum exit then
+    realnum-type istype? if printrealnum 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
+    primitive-proc-type istype? if printprim exit then
+    compound-proc-type istype? if printcomp exit then
 
     bold fg red ." Error printing expression - unrecognized type. Aborting" reset-term cr
     abort
@@ -855,6 +1256,216 @@ defer print
 
 \ }}}
 
+\ ---- Garbage Collection ---- {{{
+
+variable gc-enabled
+false gc-enabled !
+
+variable gc-stack-depth
+
+: enable-gc
+    depth gc-stack-depth !
+    true gc-enabled ! ;
+
+: disable-gc
+    false gc-enabled ! ;
+
+: gc-enabled?
+    gc-enabled @ ;
+
+: pairlike? ( obj -- obj bool )
+    pair-type istype? if true exit then
+    string-type istype? if true exit then
+    symbol-type istype? if true exit then
+    compound-proc-type istype? if true exit then
+
+    false
+;
+
+: pairlike-marked? ( obj -- obj bool )
+    over nextfrees + @ 0=
+;
+
+: mark-pairlike ( obj -- obj )
+        over nextfrees + 0 swap !
+;
+
+: gc-unmark ( -- )
+    scheme-memsize 0 do
+        1 nextfrees i + !
+    loop
+;
+
+: gc-mark-obj ( obj -- )
+
+    pairlike? invert if 2drop exit then
+    pairlike-marked? if 2drop exit then
+
+    mark-pairlike
+
+    drop pair-type 2dup
+
+    car recurse
+    cdr recurse
+;
+
+: gc-sweep
+    scheme-memsize nextfree !
+    0 scheme-memsize 1- do
+        nextfrees i + @ 0<> if
+            nextfree @ nextfrees i + !
+            i nextfree !
+        then
+    -1 +loop
+;
+
+\ Following a GC, this gives the amount of free memory
+: gc-count-marked
+    0
+    scheme-memsize 0 do
+        nextfrees i + @ 0= if 1+ then
+    loop
+;
+
+\ Debugging word - helps spot memory that is retained
+: gc-zero-unmarked
+    scheme-memsize 0 do
+        nextfrees i + @ 0<> if
+            0 car-cells i + !
+            0 cdr-cells i + !
+        then
+    loop
+;
+
+:noname
+    \ ." GC! "
+
+    gc-unmark
+
+    symbol-table obj@ gc-mark-obj
+    global-env obj@ gc-mark-obj
+
+    depth gc-stack-depth @ do
+        PSP0 i + 1 + @
+        PSP0 i + 2 + @
+
+        gc-mark-obj
+    2 +loop
+
+    gc-sweep
+
+    \ ." (" gc-count-marked . ." pairs marked as used.)" cr
+; is collect-garbage
+
+\ }}}
+
+\ ---- Primitives ---- {{{
+
+: make-primitive ( cfa -- )
+    bl word
+    count
+
+    \ 2dup ." Defining primitive " type ." ..." cr
+
+    cstr>charlist
+    drop symbol-type
+    
+    2dup
+
+    symbol-table obj@
+    cons
+    symbol-table obj!
+
+    rot primitive-proc-type ( var prim )
+    global-env obj@ define-var
+;
+
+: arg-count-error
+            bold fg red ." Incorrect argument count." reset-term cr
+            abort
+;
+
+: ensure-arg-count ( args n -- )
+    dup 0= if
+        drop nil objeq? false = if
+            arg-count-error
+        then
+    else
+        -rot 2dup nil objeq? if
+            arg-count-error
+        then
+        
+        cdr rot 1- recurse
+    then
+;
+
+: arg-type-error
+            bold fg red ." Incorrect argument type." reset-term cr
+            abort
+;
+
+: ensure-arg-type ( arg type -- arg )
+    istype? false = if
+        arg-type-error
+    then
+;
+
+include scheme-primitives.4th
+
+\ }}}
+
+\ ---- Loading files ---- {{{
+
+: charlist>cstr ( charlist addr -- n )
+
+    dup 2swap ( origaddr addr charlist )
+
+    begin 
+        2dup nil objeq? false =
+    while
+        2dup cdr 2swap car 
+        drop ( origaddr addr charlist char )
+        -rot 2swap ( origaddr charlist addr char )
+        over !
+        1+ -rot ( origaddr nextaddr charlist )
+    repeat
+
+    2drop ( origaddr finaladdr ) 
+    swap -
+;
+
+: load ( addr n -- finalResult )
+    open-input-file
+
+    empty-parse-str
+
+    ok-symbol ( port res )
+
+    begin
+        2over read-port ( port res obj )
+
+        2dup EOF character-type objeq? if
+            2drop 2swap close-port
+            exit
+        then
+
+        2swap 2drop ( port obj )
+
+        global-env obj@ eval ( port res )
+    again
+;
+
+:noname ( args -- finalResult )
+    2dup 1 ensure-arg-count
+    car string-type ensure-arg-type
+
+    drop pair-type
+    pad charlist>cstr
+    pad swap load
+; make-primitive load
+
+\ }}}
+
 \ ---- REPL ----
 
 : repl
@@ -863,12 +1474,23 @@ defer print
 
     empty-parse-str
 
+    enable-gc
+
     begin
         cr bold fg green ." > " reset-term
-        read
-        global-env fetchobj eval
+        read-console
+
+        2dup EOF character-type objeq? if
+            bold fg blue ." Moriturus te saluto." reset-term cr
+            exit
+        then
+
+        global-env obj@ eval
+
         fg cyan ." ; " print reset-term
     again
 ;
 
 forth definitions
+
+\ vim:fdm=marker