The mobile frame model

syntax Concrete syntax TConst c, where c = [+ j ]0; 1; 2; : : : TRef f , where f = F0;F1; : : : TName x , where x = proto;a;b; : : : TSelf self TVar same as TName TFunc func(x) t , where t = some term TApp tf ta TSeq t1; t2 TCall f :x(t) TAssign f .x := t TOp ta op tb , where op = + j j j : : : TIf if tcond then ttrue else tfalse TOptput print t TFork fork t TGo go p, where p = a place name TClone clone p TFrame { xi: ti, : : : } TLet let xi = ti, : : : in t Table 3: A sample concrete syntax for Term 313 a = Nm "a" 314 b = Nm "b" 315 x = Nm "x" 316 y = Nm "y" 317 z = Nm "z" 318 319 reps1 = run (TSeq (TAssign TSelf (TName NProto) 320 (TFrame "here" 321 [NProto:= (TFrame "there" 322 [x:= TConst 123, 323 y:= TConst 456]), 324 a:= TConst 1, 325 b:= TConst 2])) 326 (TSeq (TOutput (TOp (-) (TVar b) (TConst 7))) 327 (TSeq (TOutput (TOp (+) (TVar x) (TVar y))) 328 (TOutput (TVar z))))) The corresponding term in concrete syntax is: 329 self._proto := {_proto: {x: 123, 330 y: 456}, 331 a: 1, 332 b: 2}; 333 print b+7; 334 print x+y; 335 print z Running this produces the following output (here and in the following listings, an asterisk (*) indicates an operating system “tick”): 336 [*, 337 OS -> F0.0 : Return F1, *, 338 OS -> F0.0 : Return F2, *,