写伪代码时，有没有用到 let in 这种结构的。这是什么关系啊。

给个例子吧。
我猜了两种。
1) list.append(element)
2) if element in list: ...

Pseudo Code 11.10.
1 function reachabilityAndRadius(G = (V; E); s) =
2 let
3 % requires: X = fu 2 V j G(s; u) < ig ^
4 F = fu 2 V j G(s; u) = ig
5 % returns: (RG(s); maxf G(s; u) : u 2 RG(s)g)
6 function BFS(X; F; i) =
7 if jFj = 0 then (X; i)
8 else
9 let
10 X0 = X [ F ( Visit the Frontier )
11 N = NG(F) ( Determine the neighbors of the frontier )
12 F
0 = N n X0
( Remove vertices that have been visited )
13 in BFS(X0
; F0
; i + 1) end ( Next level )
14 in BFS(fg; fsg; 0) end