Storing the LU decomposition of a matrix

[mthelm85]

This section of the manual might help clear things up: Scope of Variables · The Julia Language

Inside your logpdf! function, Y = lu(x) rebinds Y to a new value lu(X), but only within the function’s local scope. This doesn’t affect the global Y because it’s a different Y that only exists inside your function. Your local Y shadows the Y passed as the argument.

And if you find all this a bit confusing, you’re not alone:

The manual's section on variable scope sucks

I know it’s not for the lack of trying, but the manual’s section on scope is unclear if not outright wrong. Issue 1 The manual says: If you assign to an existing local, it always [emphasis not mine] updates that existing local: you can only shadow a local by explicitly declaring a new local in a nested scope with the local keyword. a few lines below, it says: When x = occurs in a local scope, Julia applies the following rules to decide what the expression means based on where the assign…