Initial values specified for x, y, ... are evaluated before x, y,... are cleared.
It's from the Details in The reference to Block. And I can't understand it.
When are the local variables cleared and what's the meaning of "initial values are evaluated"?
Could anyone give an example to illustrate it? Thanks a lot!
You have to read this together with the second bullet point:
When you execute a block, values assigned to x, y, … are cleared. When the execution of the block is finished, the original values of these symbols are restored.
Now look at the following example:
x = 3;
Block[{x = x}, Print[x]]
(* 3 *)
If symbols were cleared before the initial values were evaluated, then the output of the code would be x.
x = 3;
Block[{x = (Clear[x]; x)}, Print[x]]
(* x *)
