diff options
Diffstat (limited to 'src/interp/lisp-backend.boot')
| -rw-r--r-- | src/interp/lisp-backend.boot | 42 |
1 files changed, 31 insertions, 11 deletions
diff --git a/src/interp/lisp-backend.boot b/src/interp/lisp-backend.boot index 36075241..6354a5cf 100644 --- a/src/interp/lisp-backend.boot +++ b/src/interp/lisp-backend.boot @@ -55,27 +55,39 @@ module lisp_-backend where --% 3. predicate guarding loop body execution --% 4. loop termination predicate +++ Dummy free var name. +$freeVarName == KEYWORD::freeVar + +loopVarInit(x,y) == + x is ['%free,:id] => [id,[$freeVarName,middleEndExpand ['%LET,id,y]]] + if x is ['%local,:.] then + x := x.rest + [x,[x,middleEndExpand y]] + ++ Generate code that sequentially visits each component of a list. expandIN(x,l,early?) == g := gensym() -- rest of the list yet to be visited early? => -- give the loop variable a wider scope. - [[[g,middleEndExpand l],[x,'NIL]], + [x,init] := loopVarInit(x,'%nil) + [[[g,middleEndExpand l],init], nil,[['SETQ,g,['CDR,g]]], nil,[['NOT,['CONSP,g]],['PROGN,['SETQ,x,['CAR,g]],'NIL]]] + [x,init] := loopVarInit(x,['%head,g]) [[[g,middleEndExpand l]], - [[x,['CAR,g]]],[['SETQ,g,['CDR,g]]], + [init],[['SETQ,g,['CDR,g]]], nil,[['NOT,['CONSP,g]]]] expandON(x,l) == - [[[x,middleEndExpand l]],nil,[["SETQ",x,["CDR",x]]],nil,[["ATOM",x]]] + [x,init] := loopVarInit(x,l) + [[init],nil,[["SETQ",x,["CDR",x]]],nil,[["ATOM",x]]] ++ Generate code that traverses an interval with lower bound 'lo', ++ arithmetic progression `step, and possible upper bound `final'. expandSTEP(id,lo,step,final)== - lo := middleEndExpand lo step := middleEndExpand step final := middleEndExpand final - loopvar := [[id,lo]] + [id,init] := loopVarInit(id,lo) + loopvar := [init] inc := atomic? step => step g1 := gensym() @@ -133,6 +145,16 @@ expandIterators iters == it is ["%init",var,val] => expandInit(var,val) nil +massageFreeVarInits(body,inits) == + inits = nil => body + inits is [[var,init]] and sameObject?(var,$freeVarName) => + ['SEQ,init,['EXIT,body]] + for init in inits repeat + sameObject?(init.first,$freeVarName) => + init.first := gensym() + ['LET,inits,body] + + expandLoop ['%loop,:iters,body,ret] == itersCode := expandIterators iters itersCode = "failed" => systemErrorHere ["expandLoop",iters] @@ -145,25 +167,23 @@ expandLoop ['%loop,:iters,body,ret] == 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] + body := massageFreeVarInits(body,bodyInits) exits := ["COND", [mkpf(exits,"OR"),["RETURN",expandToVMForm ret]], [true,body]] body := ["LOOP",exits,:cont] -- Finally, set up loop-wide initializations. - loopInits = nil => body - ["LET",loopInits,body] + massageFreeVarInits(body,loopInits) ++ 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]] + body := ['%store,val,['%pair,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 ['%loop,:iters,["%init",val,nil],body,["reverse!",val]] + expandLoop ['%loop,:iters,["%init",val,nil],body,['%lreverse!,val]] expandList(x is ['%list,:args]) == args := [expandToVMForm arg for arg in args] |