On Saturday, November 21, 2015 18:03:05 SimonN via Digitalmars-d-learn wrote: > string a = "hello"; > string b = a[3 .. 2]; > > I expect b to become an empty slice, because 3 is >= 2 already > after 0 increments, making the slice length 0. Instead, the code > throws a range violation. > > Expressions of this kind come up, e.g., when taking slices near > the end of arrays, like "slice = a[b.length .. $];". To make this > robust, I need an extra check for b.length > a.length, returning > null in this case, otherwise a[b.length .. $]. > > What's the design reason to prefer throwing over returning an > empty slice?
The reason is that you're providing incorrect values. How does the runtime know that you're not just providing it garbage values? D arrays are designed with the requirement that you provide valid indices when indexing or slicing them, and it's considered a logic bug to provide anything other than valid indices in a valid order. If you want your code to use indices that are invalid or which are in an invalid order, then you're going to have to create a wrapper. - Jonathan M Davis
