[Grace-core] [minigrace] Need more string functionality (#52)

[Michael Homer]

On Fri, Aug 22, 2014 at 9:25 AM, James Noble <kjx at ecs.vuw.ac.nz> wrote:
>
> On 22/08/2014, at 06:56 am, Kim Bruce <kim at cs.pomona.edu> wrote:
>
>> As for Andrew's question why we need the variant that starts at an arbitrary index, the reasons are purely efficiency.  If you are searching for all occurrences of a phrase in a large text (e.g., a book) then making all those substrings will be very inefficient.  We could argue that doesn't matter (efficiency has been a low priority for us), going from a linear to quadratic algorithm to find all occurrences of a substring grates a bit!
>
> We've always said *absolute* speed isn't a priority,
> but we've also said we don't want to mislead students or reward bad practice.
> Going from linear to quadratic, or going slower with type declarations, are misleading.
I can't see any reason at all that making (immutable!) substrings
needs to be a linear-time operation, if that's really what you care
about.
-Michael