> And what does "no way to escape the language's type rules" mean?
I can give you an example, from bitter experience.
In the original Pascal, the size of an array was part of the type of an array. There was no possible type for a variable-sized array. And you couldn't cast from an array of one fixed size to an array of another fixed size.
Well, we were trying to do a 2D numerical simulation on a grid, with the size of the grid being user-specified. The original version of the program used a linked list to simulate the array, since you could have an arbitrarily-long linked list. But this meant that, if the simulation was 60x60, to reference the cell directly below the current one, you had to follow 60 links to get there!
I replaced it with a 2D array of a fixed size, with the size being the largest amount we could fit into available memory (it was on an embedded system, so the amount of memory available was predictable). Of that, we used only the user-specified subset to do the simulation.
TL;DR: If you need to do something that's outside what's allowed by your type system, and there's no way to escape the language's type system, you're trapped.
I can give you an example, from bitter experience.
In the original Pascal, the size of an array was part of the type of an array. There was no possible type for a variable-sized array. And you couldn't cast from an array of one fixed size to an array of another fixed size.
Well, we were trying to do a 2D numerical simulation on a grid, with the size of the grid being user-specified. The original version of the program used a linked list to simulate the array, since you could have an arbitrarily-long linked list. But this meant that, if the simulation was 60x60, to reference the cell directly below the current one, you had to follow 60 links to get there!
I replaced it with a 2D array of a fixed size, with the size being the largest amount we could fit into available memory (it was on an embedded system, so the amount of memory available was predictable). Of that, we used only the user-specified subset to do the simulation.
TL;DR: If you need to do something that's outside what's allowed by your type system, and there's no way to escape the language's type system, you're trapped.