note about tail call optimization in relevance to solving problems recursiively

370/notes/dynamic.md

@@ -4,7 +4,7 @@
 > Take a large problem
 > Break it up
 > Solve the pieces
-/lecture
+
 
 
 # Definitions
@@ -16,3 +16,38 @@ _Recursive dynamic programming_
 _Tabulation_
 :	Bottom up approach
 :	Go from little problems and build up
+
+
+# Recursive compiler tricks
+
+Normal iterative: 
+```
+start:
+...
+jcond start
+```
+
+Normal recursion(under non-priveleged procs):
+
+Each "iteration" creates a new frame of whatever size:
+hence we approach the hard stack limit
+
+_Sick guess_:
+```
+	At compile we should be able to predict an incoming iteration from a 
+	recusive endpoint.
+
+	? is it just parameterized jumps ?
+```
+
+_Answer:_ 
+```
+	Tail recusion optimization
+
+	Takes the last statement of function 
+	Assuming its a recursive call, we can replace our current stack frame's arguments
+	The only state that changes between calls then is just the arguments
+```
+In this sense we are turning a recusive functino into an iterative one because the whole state is held in one frame & we only ever jump within our routines address space.
+
+However, this tail optimization can only happen at the tail of a routine.