Tiny refactor.

[scheme.forth.jl.git] / scheme.4th

diff --git a/scheme.4th b/scheme.4th
index 3014bea..1f02114 100644 (file)
--- a/scheme.4th
+++ b/scheme.4th
@@ -82,6 +82,20 @@ variable nextfree
 : 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>
+;
+
 \ }}}
 
 \ ---- Pre-defined symbols ---- {{{
@@ -121,13 +135,12 @@ 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
 
 \ }}}
 
 \ ---- Environments ---- {{{
 
-objvar global-env
-
 : enclosing-env ( env -- env )
     cdr ;
 
@@ -145,9 +158,9 @@ objvar global-env
 
 : 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 )
@@ -185,7 +198,7 @@ objvar vals
         2dup nil objeq? false =
     while
         2over 2over first-frame
-        lookup-var-frame if
+        get-vars-vals-frame if
             2drop 2drop
             vars fetchobj vals fetchobj true
             exit
@@ -205,7 +218,7 @@ 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
 ;
 
@@ -215,22 +228,22 @@ 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 objset 
+    env setobj 
 
-    2over env objfetch ( var val var env )
+    2over env fetchobj ( var val var env )
     get-vars-vals if
         2swap 2drop ( var val vals )
         set-car!
         2drop
     else
-        env objfetch
+        env fetchobj
         first-frame ( var val frame )
         add-binding
     then
@@ -238,6 +251,10 @@ objvar env
 
 hide env
 
+objvar global-env
+nil nil nil extend-env
+global-env setobj
+
 \ }}}
 
 \ ---- Read ---- {{{
@@ -667,6 +684,8 @@ defer read
 
 \ ---- Eval ---- {{{
 
+defer eval
+
 : self-evaluating? ( obj -- obj bool )
     boolean-type istype? if true exit then
     number-type istype? if true exit then
@@ -704,7 +723,7 @@ defer read
     cdr cdr car ;
 
 : assignment? ( obj -- obj bool )
-    set-symbol tagged-list? ;
+    set!-symbol tagged-list? ;
 
 : assignment-var ( obj -- var )
     cdr car ;
@@ -720,7 +739,7 @@ defer read
     
     2swap definition-var 2swap ( env var val )
 
-    >R >R 2swap R> R> 2swap ( var val env )
+    2rot ( var val env )
     define-var
 
     ok-symbol
@@ -734,12 +753,41 @@ defer read
     
     2swap assignment-var 2swap ( env var val )
 
-    >R >R 2swap R> R> 2swap ( var val env )
+    2rot ( var val env )
     set-var
 
     ok-symbol
 ;
-: eval ( obj env -- result )
+
+: 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 -- boolean )
+    false? invert ;
+
+:noname ( obj env -- result )
     2swap
 
     self-evaluating? if
@@ -768,9 +816,23 @@ defer read
         exit
     then
 
+    if? if
+        2over 2over
+        if-predicate
+        2swap eval 
+
+        true? if
+            if-consequent
+        else
+            if-alternative
+        then
+
+        2swap ['] eval goto
+    then
+
     bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr
     abort
-;
+; is eval
 
 \ }}}
 
@@ -867,3 +929,5 @@ defer print
 ;
 
 forth definitions
+
+\ vim:fdm=marker