Sure, but the article doesn't define optimal substructure, nor does it give a general statement about it. It just talks about a specific implication that _would be_ true if code size had optimal substructure as I thought (but based on my comment above, it seems I proved myself wrong).
> Now, let's say you split the function in two parts and you find their minimums independently. Optimal substructure tells us that if you just merge these two, you'll get the minimum version of the whole function.
Optimal substructure doesn't tell us this. I don't know whether or not this problem has optimal substructure, but even if it did, it still wouldn't tell us this.
Optimal substructure means it is possible to construct an optimal solution from optimal solutions to its subproblems; it doesn't mean that optimal solutions to arbitrary pair of subproblems (that compose to form the complete problem) can be used to form an optimal solution, which is what I understood the quoted section of the article to be saying.
