X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?p=scheme.forth.jl.git;a=blobdiff_plain;f=src%2Fscheme.4th;h=ec97f09761c26f8603c14001277cd08b6f5e7dd8;hp=6e2c49255a788a7293646ee0c5a751aab51dd7f9;hb=724ff46a1b082bef48b310a85d5a82037c2a914c;hpb=5eea24f47ad60b69af59a76c7285ec232c29009c

diff --git a/src/scheme.4th b/src/scheme.4th
index 6e2c492..ec97f09 100644
--- a/src/scheme.4th
+++ b/src/scheme.4th
@@ -10,6 +10,7 @@ include float.4th
 include debugging.4th
 
 defer read
+defer expand
 defer eval
 defer print
 
@@ -261,8 +262,8 @@ 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
 create-symbol eof               eof-symbol
+create-symbol no-match          no-match-symbol
 
 \ Symbol to be bound to welcome message procedure by library
 create-symbol welcome           welcome-symbol
@@ -1403,34 +1404,21 @@ defer eval-quasiquote-item
 : definition? ( obj -- obj bool )
     define-symbol tagged-list? ;
 
-: make-lambda ( params body -- lambda-exp )
-    lambda-symbol -2rot cons cons ;
-
-( Handles iterative expansion of defines in
-  terms of nested lambdas. Most Schemes only
-  handle one iteration of expansion! )
-: definition-var-val ( obj -- var val )
-
-    cdr 2dup cdr 2swap car ( val var )
-
-    begin
-        symbol-type istype? false =
-    while
-        2dup cdr 2swap car ( val formals var' )
-        -2rot 2swap ( var' formals val )
-        make-lambda nil cons ( var' val' )
-        2swap ( val' var' )
-    repeat
+: definition-var ( obj -- var )
+    cdr car ;
 
-    2swap car
-;
+: definition-val ( obj -- val )
+    cdr cdr car ;
 
 : eval-definition ( obj env -- res )
-    2dup 2rot ( env env obj )
-    definition-var-val ( env env var val )
-    2rot eval  ( env var val )
+    2swap
+    2over 2over
+    definition-val 2swap
+    eval
 
-    2rot ( var val env )
+    2swap definition-var 2swap
+
+    2rot
     define-var
 
     ok-symbol
@@ -1524,12 +1512,6 @@ hide env
 : lambda-body ( obj -- body )
     cdr cdr ;
 
-: 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
@@ -1652,24 +1634,10 @@ hide env
                 R> drop ['] eval goto-deferred  \ Tail call optimization
             endof
 
-            except-message: ." object not applicable." recoverable-exception throw
+            except-message: ." object '" drop print ." ' not applicable." recoverable-exception throw
         endcase
 ;
 
-( Simply evaluates the given procedure with expbody as its argument. )
-: macro-expand ( 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 )
-    
-    -2rot 2swap
-    flatten-proc-args
-    2swap 2rot
-
-    extend-env eval-sequence eval
-;
-
 :noname ( obj env -- result )
     2swap
 
@@ -1738,45 +1706,171 @@ hide env
         exit
     then
 
-    begin? if
-        begin-actions 2swap
-        eval-sequence
-        ['] eval goto-deferred
-    then
-
     application? if
 
         2over 2over ( env exp env exp )
         operator ( env exp env opname )
 
-        2dup lookup-macro nil? false = if
-             \ Macro function evaluation
+        2swap eval ( env exp proc )
 
-            ( env exp env opname mproc )
-            2swap 2drop -2rot 2drop cdr ( env mproc body )
+        -2rot ( proc env exp )
+        operands 2swap ( proc operands env )
+        list-of-vals ( proc argvals )
 
-            macro-expand
+        apply
+        exit
+    then
 
-            2swap
-            ['] eval goto-deferred
-        else
-           \ Regular function application
+    except-message: ." tried to evaluate object with unknown type." recoverable-exception throw
+; is eval
 
-            2drop ( env exp env opname )
+\ }}}
 
-            2swap eval ( env exp proc )
+\ ---- Macro Expansion ---- {{{
 
-            -2rot ( proc env exp )
-            operands 2swap ( proc operands env )
-            list-of-vals ( proc argvals )
+( 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 )
+    
+    -2rot 2swap
+    flatten-proc-args
+    2swap 2rot
 
-            apply
-            exit
-        then
+    extend-env eval-sequence eval
+;
+
+: 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
+
+    2over cdr macro-eval
+
+    2dup no-match-symbol objeq? if
+        2drop exit
+    else
+        2swap 2drop
     then
 
-    except-message: ." tried to evaluate object with unknown type." recoverable-exception throw
-; is eval
+    R> drop ['] expand goto-deferred
+;
+
+: expand-quasiquote-item ( exp -- result )
+    nil? if exit then
+
+    unquote? if
+        unquote-symbol 2swap cdr car expand nil cons cons
+        exit
+    then
+
+    unquote-splicing? if
+        unquote-splicing-symbol 2swap cdr car expand nil cons cons
+        exit
+    then
+    
+    pair-type istype? if
+        2dup car recurse
+        2swap cdr recurse
+        cons
+    then
+;
+
+: expand-quasiquote ( exp -- result )
+    quasiquote-symbol 2swap cdr
+
+    expand-quasiquote-item
+
+    cons ;
+
+: expand-definition ( exp -- result )
+    define-symbol 2swap
+
+    2dup definition-var
+    2swap definition-val expand
+    nil ( define var val' nil )
+
+    cons cons cons ;
+
+: expand-assignment ( exp -- result )
+    set!-symbol 2swap
+
+    2dup assignment-var
+    2swap assignment-val expand
+    nil ( define var val' nil )
+
+    cons cons cons ;
+
+: expand-list ( exp -- res )
+    nil? if exit then
+
+    2dup car expand
+    2swap cdr recurse
+
+    cons ;
+
+: macro-definition-nameparams
+    cdr car ;
+
+: expand-define-macro ( exp -- res )
+    define-macro-symbol 2swap
+    2dup macro-definition-nameparams
+    2swap macro-definition-body expand-list
+
+    cons cons ;
+
+: expand-lambda ( exp -- res )
+    lambda-symbol 2swap
+    2dup lambda-parameters
+    2swap lambda-body expand-list
+
+    cons cons ;
+
+: expand-if ( exp -- res )
+    if-symbol 2swap
+    
+    2dup if-predicate expand
+    2swap 2dup if-consequent expand
+    2swap if-alternative none? if
+        2drop nil
+    else
+        expand nil cons
+    then
+
+    cons cons cons ;
+
+: expand-application ( exp -- res )
+    2dup operator expand
+    2swap operands expand-list
+
+    cons ;
+
+:noname ( exp -- result )
+    expand-macro
+
+    self-evaluating? if exit then
+
+    quote? if exit then
+
+    quasiquote? if expand-quasiquote exit then
+
+    definition? if expand-definition exit then
+
+    assignment? if expand-assignment exit then
+
+    macro-definition? if expand-define-macro exit then
+
+    lambda? if expand-lambda exit then
+
+    if? if expand-if exit then
+
+    application? if expand-application exit then
+
+; is expand
 
 \ }}}
 
@@ -2004,6 +2098,8 @@ variable gc-stack-depth
 
         2swap 2drop ( port obj )
 
+        expand
+
         global-env obj@ eval ( port res )
     again
 ;
@@ -2032,6 +2128,8 @@ variable gc-stack-depth
         true exit
     then
 
+    expand
+
     global-env obj@ eval
 
     fg cyan ." ; " print reset-term