X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=src%2Fscheme.4th;h=68c3b67478f16ffa10bdbc659ebd10810d6e0a90;hb=722badbcc9d3453b18df83c95a935c095a23d4a6;hp=a32ee45a8d10b5c315fc3f8aceab42bafe3ecd8d;hpb=6cb6a8d3e4449a1cf70ac4cbb0b88cf2c38d6434;p=scheme.forth.jl.git

diff --git a/src/scheme.4th b/src/scheme.4th
index a32ee45..68c3b67 100644
--- a/src/scheme.4th
+++ b/src/scheme.4th
@@ -62,7 +62,7 @@ variable nextexception
 make-exception recoverable-exception
 make-exception unrecoverable-exception
 
-: throw reset-term throw ;
+: throw reset-term cr throw ;
 
 \ }}}
 
@@ -75,6 +75,12 @@ create car-type-cells scheme-memsize allot
 create cdr-cells scheme-memsize allot
 create cdr-type-cells scheme-memsize allot
 
+variable gc-enabled
+false gc-enabled !
+
+: gc-enabled?
+    gc-enabled @ ;
+
 create nextfrees scheme-memsize allot
 :noname
     scheme-memsize 0 do
@@ -90,7 +96,9 @@ variable nextfree
     nextfree !
 
     nextfree @ scheme-memsize >= if
-        collect-garbage
+        gc-enabled? if
+            collect-garbage
+        then
     then
 
     nextfree @ scheme-memsize >= if
@@ -402,6 +410,9 @@ variable read-line-buffer-offset
 : make-frame ( vars vals -- frame )
     cons ;
 
+: add-frame-to-env ( frame env -- env )
+    cons ;
+
 : frame-vars ( frame -- vars )
     car ;
 
@@ -416,99 +427,89 @@ variable read-line-buffer-offset
 ;
 
 : extend-env ( vars vals env -- env )
-    >R >R
-    make-frame
-    R> R>
-    cons
+    -2rot make-frame
+    2swap add-frame-to-env
 ;
 
-objvar vars
-objvar vals
-
-: get-vars-vals-frame ( var frame -- bool )
-    2dup frame-vars vars obj!
-    frame-vals vals obj!
+: get-vals-frame ( var frame -- vals | nil )
+    2dup frame-vars 
+    2swap frame-vals ( var vars vals )
 
     begin
-        vars obj@ nil objeq? false =
+        nil? false =
     while
-        2dup vars obj@ car objeq? if
-            2drop true
+
+        -2rot ( vals var vars )
+        2over 2over car objeq? if
+            2drop 2drop
             exit
         then
 
-        vars obj@ cdr vars obj!
-        vals obj@ cdr vals obj!
+        cdr 2rot cdr
     repeat
 
-    2drop false
+    2drop 2drop 2drop
+    nil
 ;
 
-: get-vars-vals ( var env -- vars? vals? bool )
+: get-vals ( var env -- vals | nil )
 
     begin
         nil? false =
     while
         2over 2over first-frame
-        get-vars-vals-frame if
-            2drop 2drop
-            vars obj@ vals obj@ true
+        get-vals-frame nil? false = if
+            2swap 2drop 2swap 2drop
             exit
         then
 
+        2drop
+
         enclosing-env
     repeat
 
-    2drop 2drop
-    false
+    2swap 2drop
 ;
 
-hide vars
-hide vals
-
-objvar var
-
+objvar var \ Used only for error messages
 : lookup-var ( var env -- val )
     2over var obj!
-    get-vars-vals if
-        2swap 2drop car
-    else
-        except-message: ." tried to read unbound variable '" var obj@ print ." '." recoverable-exception  throw
+    
+    get-vals nil? if
+        except-message: ." tried to read unbound variable '" var obj@ print ." '."
+        recoverable-exception throw
     then
+
+    car
 ;
 
 : set-var ( var val env -- )
-    >R >R 2swap R> R> ( val var env )
-    2over var obj!
-    get-vars-vals if
-        2swap 2drop ( val vals )
-        set-car!
+    2rot 2dup var obj! ( val env var )
+    get-vals nil? if
+        except-message: ." tried to set unbound variable '" var obj@ print ." '."
+        recoverable-exception throw
     else
-        except-message: ." tried to set unbound variable '" var obj@ print ." '." recoverable-exception throw
+        ( val vals )
+        set-car!
     then
 ;
-
 hide var
 
-objvar env
-
 : define-var ( var val env -- )
-    env obj! 
+    first-frame ( var val frame )
+    2rot 2swap 2over 2over ( val var frame var frame )
 
-    2over env obj@ ( var val var env )
-    get-vars-vals if
-        2swap 2drop ( var val vals )
-        set-car!
+    get-vals-frame nil? if
         2drop
-    else
-        env obj@
-        first-frame ( var val frame )
+        -2rot 2swap 2rot
         add-binding
+    else
+        ( val var frame vals )
+        2swap 2drop 2swap 2drop
+        set-car!
     then
 ;
 
-hide env
-
 : make-procedure ( params body env -- proc )
     nil
     cons cons cons
@@ -1273,6 +1274,11 @@ parse-idx-stack parse-idx-sp !
         exit
     then
 
+    nextchar [char] ) = if
+        inc-parse-idx
+        except-message: ." unmatched closing parenthesis." recoverable-exception throw
+    then
+
     \ Anything else is parsed as a symbol
     readsymbol charlist>symbol
 
@@ -1286,7 +1292,7 @@ parse-idx-stack parse-idx-sp !
 
 \ }}}
 
-\ ---- Eval ---- {{{
+\ ---- Syntax ---- {{{
 
 : self-evaluating? ( obj -- obj bool )
     boolean-type istype? if true exit then
@@ -1327,20 +1333,6 @@ parse-idx-stack parse-idx-sp !
 : definition-val ( obj -- val )
     cdr cdr car ;
 
-: eval-definition ( obj env -- res )
-    2swap
-    2over 2over
-    definition-val 2swap
-    eval
-
-    2swap definition-var 2swap
-
-    2rot
-    define-var
-
-    ok-symbol
-;
-
 : assignment? ( obj -- obj bool )
     set!-symbol tagged-list? ;
 
@@ -1350,20 +1342,6 @@ parse-idx-stack parse-idx-sp !
 : assignment-val ( obj -- val )
     cdr cdr car ;
 
-: 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 )
-
-    2rot ( var val env )
-    set-var
-
-    ok-symbol
-;
-
 : macro-definition? ( obj -- obj bool )
     define-macro-symbol tagged-list? ;
 
@@ -1376,22 +1354,6 @@ parse-idx-stack parse-idx-sp !
 : macro-definition-body ( exp -- body )
     cdr cdr ;
 
-objvar env
-: eval-define-macro ( obj env -- res )
-    env obj!
-
-    2dup macro-definition-name 2swap ( name obj )
-    2dup macro-definition-params 2swap ( name params obj )
-    macro-definition-body ( name params body )
-
-    env obj@ ( name params body env )
-
-    make-macro
-
-    ok-symbol
-;
-hide env
-
 : if? ( obj -- obj bool )
     if-symbol tagged-list? ;
 
@@ -1429,32 +1391,6 @@ hide env
 : lambda-body ( obj -- body )
     cdr 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
-    nil? if
-        2drop none
-        2swap exit
-    then
-
-    begin
-        2dup cdr ( env explist nextexplist )
-        nil? 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? ;
 
@@ -1473,18 +1409,6 @@ hide env
 : 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 ;
 
@@ -1531,7 +1455,7 @@ hide env
 
 \ }}}
 
-\ ---- Analyze ----
+\ ---- Analyze ---- {{{
 
 : evaluate-eproc ( eproc env --- res )
 
@@ -1610,28 +1534,6 @@ hide env
     nil cons cons cons
 ;
 
-: if-executor ( cproc aproc pproc env -- res )
-    2swap 2over ( cproc aproc env pproc env -- res )
-    evaluate-eproc
-
-    true? if
-        2swap 2drop
-    else
-        2rot 2drop
-    then
-
-    evaluate-eproc
-;
-
-: analyze-if ( exp -- eproc )
-    2dup if-predicate analyze
-    2swap 2dup if-consequent analyze
-    2swap if-alternative analyze
-
-    ['] if-executor primitive-proc-type
-    nil cons cons cons cons
-;
-
 : sequence-executor ( eproc-list env -- res )
     2swap
 
@@ -1639,7 +1541,6 @@ hide env
         2dup cdr ( env elist elist-rest)
         nil? invert
     while
-
         -2rot car 2over ( elist-rest env elist-head env )
         evaluate-eproc  ( elist-rest env head-res )
         2drop 2swap     ( env elist-rest )
@@ -1665,6 +1566,42 @@ hide env
     nil cons cons
 ;
 
+
+: macro-definition-executor  ( name params bproc env -- ok )
+    make-macro ok-symbol
+;
+
+: analyze-macro-definition ( exp -- eproc )
+    2dup macro-definition-name
+    2swap 2dup macro-definition-params
+    2swap macro-definition-body analyze-sequence
+
+    ['] macro-definition-executor primitive-proc-type
+    nil cons cons cons cons
+;
+
+: if-executor ( cproc aproc pproc env -- res )
+    2swap 2over ( cproc aproc env pproc env -- res )
+    evaluate-eproc
+
+    true? if
+        2swap 2drop
+    else
+        2rot 2drop
+    then
+
+    ['] evaluate-eproc goto
+;
+
+: analyze-if ( exp -- eproc )
+    2dup if-consequent analyze
+    2swap 2dup if-alternative analyze
+    2swap if-predicate analyze
+
+    ['] if-executor primitive-proc-type
+    nil cons cons cons cons
+;
+
 : lambda-executor ( params bproc env -- res )
     make-procedure
     ( Although this is packaged up as a regular compound procedure,
@@ -1705,22 +1642,14 @@ hide env
     then
 ;
 
-: application-executor ( operator-proc arg-procs env -- res )
-    2rot 2over ( aprocs env fproc env )
-    evaluate-eproc ( aprocs env proc )
-
-    -2rot 2swap ( proc env aprocs )
-    evaluate-operand-eprocs ( proc vals )
-
-    2swap ( vals proc )
-    
+: apply ( vals proc )
     dup case
         primitive-proc-type of
             drop execute
         endof
 
         compound-proc-type of
-                2dup procedure-body ( argvals proc body )
+                2dup procedure-body ( argvals proc bproc )
                 -2rot 2dup procedure-params ( bproc argvals proc argnames )
                 -2rot procedure-env ( bproc argnames argvals procenv )
 
@@ -1737,6 +1666,18 @@ hide env
     endcase
 ;
 
+: application-executor ( operator-proc arg-procs env -- res )
+    2rot 2over ( aprocs env fproc env )
+    evaluate-eproc ( aprocs env proc )
+
+    -2rot 2swap ( proc env aprocs )
+    evaluate-operand-eprocs ( proc vals )
+
+    2swap ( vals proc )
+
+    ['] apply goto
+;
+
 : analyze-application ( exp -- eproc )
     2dup operator analyze
     2swap operands operand-eproc-list
@@ -1747,79 +1688,54 @@ hide env
 
 :noname ( exp --- eproc )
 
-    self-evaluating? if
-        analyze-self-evaluating
-        exit
-    then
+    self-evaluating? if analyze-self-evaluating exit then
 
-    quote? if
-        analyze-quoted
-        exit
-    then
+    quote? if analyze-quoted exit then
     
-    variable? if
-        analyze-variable
-        exit
-    then
+    variable? if analyze-variable exit then
 
-    definition? if
-        analyze-definition
-        exit
-    then
+    definition? if analyze-definition exit then
 
-\    macro-definition? if
-\        analyze-macro-definition
-\        exit
-\    then
+    assignment? if analyze-assignment exit then
 
-    assignment? if
-        analyze-assignment
-        exit
-    then
+    macro-definition? if analyze-macro-definition exit then
 
-    if? if
-        analyze-if
-        exit
-    then
+    if? if analyze-if exit then
 
-    lambda? if
-        analyze-lambda
-        exit
-    then
+    lambda? if analyze-lambda exit then
 
-    application? if
-        analyze-application
-        exit
-    then
+    application? if analyze-application exit then
 
-    
     except-message: ." tried to analyze unknown expression type." recoverable-exception throw
 
 ; is analyze
 
+\ }}}
 
 \ ---- Macro Expansion ---- {{{
 
 ( Simply evaluates the given procedure with expbody as its argument. )
 : macro-eval ( proc expbody -- result )
     2swap
-    2dup procedure-body ( expbody proc procbody )
-    -2rot 2dup procedure-params ( procbody expbody proc argnames )
-    -2rot procedure-env ( procbody argnames expbody procenv )
+    2dup procedure-body ( expbody proc bproc )
+    -2rot 2dup procedure-params ( bproc expbody proc argnames )
+    -2rot procedure-env ( bproc argnames expbody procenv )
     
     -2rot 2swap
     flatten-proc-args
     2swap 2rot
 
-    extend-env eval-sequence eval
+    extend-env ( bproc env )
+
+    ['] evaluate-eproc goto
 ;
 
 : expand-macro ( exp -- result )
     pair-type istype? invert if exit then
+
     2dup car symbol-type istype? invert if 2drop exit then
-    
-    lookup-macro nil? if
-        2drop exit then
+
+    lookup-macro nil? if 2drop exit then
 
     2over cdr macro-eval
 
@@ -2018,12 +1934,24 @@ hide env
     except-message: ." tried to print object with unknown type." recoverable-exception throw
 ; is print
 
+xxxx
 \ }}}
 
 \ ---- Garbage Collection ---- {{{
 
-variable gc-enabled
-false gc-enabled !
+( Notes on garbage collection:
+  This is a mark-sweep garbage collector, invoked by cons.
+  The roots of the object tree used by the marking routine 
+  include all objects in the parameter stack, and several
+  other fixed roots such as global-env, symbol-table, macro-table,
+  and the console-i/o-port.
+
+  NO OTHER OBJECTS WILL BE MARKED!
+
+  This places implicit restrictions on when cons can be invoked.
+  Invoking cons when live objects are stored on the return stack
+  or in other variables than the above will result in possible
+  memory corruption if the cons triggers the GC. )
 
 variable gc-stack-depth
 
@@ -2034,9 +1962,6 @@ variable gc-stack-depth
 : 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
@@ -2136,8 +2061,14 @@ variable gc-stack-depth
     ok-symbol ( port res )
 
     begin
+        \ DEBUG
+        \ bold fg blue ." READ from " 2over drop . ." ==> " reset-term
+
         2over read-port ( port res obj )
 
+        \ DEBUG
+        \ 2dup print cr
+
         2dup EOF character-type objeq? if
             2drop 2swap close-port
             exit
@@ -2155,7 +2086,11 @@ variable gc-stack-depth
 
     include scheme-primitives.4th
 
-    \ s" scheme-library.scm" load 2drop
+    enable-gc
+
+    s" scheme-library.scm" load 2drop
+
+    disable-gc
     
 \ }}}
 
@@ -2186,7 +2121,7 @@ variable gc-stack-depth
     enable-gc
 
     \ Display welcome message
-    \ welcome-symbol nil cons global-env obj@ eval 2drop
+    welcome-symbol nil cons global-env obj@ eval 2drop
 
     begin
         ['] repl-body catch
@@ -2197,6 +2132,8 @@ variable gc-stack-depth
             throw false
         endcase
     until
+
+    disable-gc
 ;
 
 forth definitions