5 files changed, 36 insertions, 22 deletions
diff --git a/src/interp/g-opt.boot b/src/interp/g-opt.boot
index 2717312a..6e0ea498 100644
--- a/src/interp/g-opt.boot
+++ b/src/interp/g-opt.boot
@@ -124,7 +124,7 @@ subrname u ==
   nil
  
 changeThrowToExit(s,g) ==
-  atom s or first s in '(QUOTE SEQ REPEAT COLLECT %collect) => nil
+  atom s or first s in '(QUOTE SEQ REPEAT COLLECT %collect %repeat) => nil
   s is ["THROW", =g,:u] => (s.first := "EXIT"; s.rest := u)
   changeThrowToExit(first s,g)
   changeThrowToExit(rest s,g)
diff --git a/src/interp/g-util.boot b/src/interp/g-util.boot
index 72c05126..8958843e 100644
--- a/src/interp/g-util.boot
+++ b/src/interp/g-util.boot
@@ -116,6 +116,9 @@ expandUNTIL p ==
   g := gensym()
   [[[g,false]],nil,[["SETQ",g,middleEndExpand p]],nil,[g]]
 
+expandInit(var,val) ==
+  [[[var,middleEndExpand val]],nil,nil,nil,nil]
+
 expandIterators iters ==
   [toLisp it or leave "failed" for it in iters] where
      toLisp it ==
@@ -125,37 +128,49 @@ expandIterators iters ==
        it is ["WHILE",pred] => expandWHILE pred
        it is [op,pred] and op in '(SUCHTHAT _|) => expandSUCHTHAT pred
        it is ["UNTIL",pred] => expandUNTIL pred
+       it is ["%init",var,val] => expandInit(var,val)
        nil
 
-++ Generate code for list comprehension.
-expandCollect ["%collect",:iters,body] ==
+expandLoop(iters,body,ret) ==
   itersCode := expandIterators iters
-  itersCode = "failed" => systemErrorHere ["expandCollect",iters]
-  val := gensym()    -- result of the list comprehension
+  itersCode = "failed" => systemErrorHere ["expandLoop",iters]
+  body := middleEndExpand body
   itersCode := "coagulate"/itersCode
     where
       coagulate(it1,it2) == [append(it1.k,it2.k) for k in 0..4]
-  [loopInits,bodyInits,cont,filters,exits,value] := itersCode
-  -- Transform the body to build the list as we go.
-  body := ["SETQ",val,["CONS",middleEndExpand body,val]]
-  -- Guard th execution of the body by the filters.
+  [loopInits,bodyInits,cont,filters,exits] := itersCode
+  -- Guard the execution of the body by the filters.
   if filters ~= nil then
     body := mkpf([:filters,body],"AND")
   -- If there is any body-wide initialization, now is the time.
   if bodyInits ~= nil then
     body := ["LET",bodyInits,body]
-  if value ~= nil then
-    value := first value
   exits := ["COND",
-             [mkpf(exits,"OR"),["RETURN",["NREVERSE",val]]],
+             [mkpf(exits,"OR"),["RETURN",ret]],
                [true,body]]
   body := ["LOOP",exits,:cont]
   -- Finally, set up loop-wide initializations.
-  ["LET",[:loopInits,[val,nil]],body]
+  loopInits = nil => body
+  ["LET",loopInits,body]
+
+++ Generate code for list comprehension.
+expandCollect ["%collect",:iters,body] ==
+  val := gensym()    -- result of the list comprehension
+  -- Transform the body to build the list as we go.
+  body := ["SETQ",val,["CONS",middleEndExpand body,val]]
+  -- Initialize the variable holding the result; expand as 
+  -- if ordinary loop.  But don't forget we built the result
+  -- in reverse order.
+  expandLoop([:iters,["%init",val,nil]],body,["NREVERSE",val])
+
+++ Generate code for plain loop.
+expandRepeat ["%repeat",:iters,body] ==
+  expandLoop(iters,body,["voidValue"])
 
 ++ Table of opcode-expander pairs.  
 $OpcodeExpanders == [
-   ["%collect",:"expandCollect"]
+   ["%collect",:"expandCollect"],
+   ["%repeat",:"expandRepeat"]
  ]
 
 ++ Return the expander of a middle-end opcode, or nil if there is none.
diff --git a/src/interp/i-map.boot b/src/interp/i-map.boot
index 9bb6bf4e..bfc99b6d 100644
--- a/src/interp/i-map.boot
+++ b/src/interp/i-map.boot
@@ -1031,7 +1031,7 @@ findLocalVars1(op,form) ==
   form is ['is,l,pattern] =>
     findLocalVars1(op,l)
     for var in listOfVariables rest pattern repeat mkLocalVar(op,var)
-  form is [oper,:itrl,body] and oper in '(REPEAT COLLECT %collect) =>
+  form is [oper,:itrl,body] and oper in '(REPEAT COLLECT %collect %repeat) =>
     findLocalsInLoop(op,itrl,body)
   form is [y,:argl] =>
     y is "Record" or (y is "Union" and argl is [[":",.,.],:.]) => 
diff --git a/src/interp/i-spec1.boot b/src/interp/i-spec1.boot
index 769af133..2b3b5ba3 100644
--- a/src/interp/i-spec1.boot
+++ b/src/interp/i-spec1.boot
@@ -572,11 +572,11 @@ interpCOLLECT(op,itrl,body) ==
   emptyAtree op
   emptyAtree itrl
   emptyAtree body
-  code := ['COLLECT,:[interpIter itr for itr in itrl],
+  code := ["%collect",:[interpIter itr for itr in itrl],
     interpCOLLECTbody(body,$indexVars,$indexTypes)]
   value := timedEVALFUN code
   t :=
-    null value => '(None)
+    null value => $None
     last $collectTypeList
   rm := ['Tuple,t]
   value := [objValUnwrap coerceInteractive(objNewWrap(v,m),t)
@@ -817,7 +817,7 @@ checkForFreeVariables(v,locals) ==
     op in '(LAMBDA QUOTE getValueFromEnvironment) => v
     op = "LETT" => -- Expands to a SETQ.
       ["SETF",:[checkForFreeVariables(a,locals) for a in args]]
-    op in '(COLLECT REPEAT %collect) => -- Introduces a new bound variable?
+    op in '(COLLECT REPEAT %collect %repeat) =>
       first(args) is ["STEP",var,:.] =>
        $boundVariables := [var,:$boundVariables]
        r := [op,:[checkForFreeVariables(a,locals) for a in args]]
diff --git a/src/interp/i-spec2.boot b/src/interp/i-spec2.boot
index d874e184..85035890 100644
--- a/src/interp/i-spec2.boot
+++ b/src/interp/i-spec2.boot
@@ -952,11 +952,10 @@ evalREPEAT(op,[:itrl,body],repeatMode) ==
   bodyCode := getArgValue(body,bodyMode)
   if $iterateCount > 0 then
     bodyCode := ["CATCH",$repeatBodyLabel,bodyCode]
-  code := ['REPEAT,:[evalLoopIter itr for itr in itrl], bodyCode]
-  if repeatMode = $Void then code := ['OR,code,'(voidValue)]
+  code := ["%repeat",:[evalLoopIter itr for itr in itrl], bodyCode]
   code := timedOptimization code
   if $breakCount > 0 then code := ['CATCH,$repeatLabel,code]
-  val:=
+  val :=
     $genValue =>
       timedEVALFUN code
       objNewWrap(voidValue(),repeatMode)
@@ -975,7 +974,7 @@ interpREPEAT(op,itrl,body,repeatMode) ==
   $indexTypes: local := NIL
   code :=
       -- we must insert a CATCH for the iterate clause
-      ["REPEAT",:[interpIter itr for itr in itrl],
+      ["%repeat",:[interpIter itr for itr in itrl],
         ["CATCH",$repeatBodyLabel,interpLoop(body,$indexVars,
           $indexTypes,nil)]]
   SPADCATCH(eval $repeatLabel,timedEVALFUN code)