13 Nov
2019
13 Nov
'19
8:37 a.m.
On 2019-Nov-12 17:49:46 -0500, Arthur Krewat <krewat(a)kilonet.net> wrote:
On 11/12/2019 5:41 PM, Robert Clausecker wrote:
> Oh please no. One of the things we've hopefully all learned from Pascal
> is that length-prefixed strings suck because you can't perform anything
> useful without copying the entire string.
Keep in mind that C doesn't have a "string" type. The use of a NUL
terminated char array is purely convention. There's nothing to stop
someone using a length-prefixed array (though there's virtually no
standard library support for that).
> Rob Pike and friends showed
> how to get strings and vectors right in the Go language where you have a
> builtin slice type which is essentially a structure
>
> struct slice(type) {
> type *data;
> size_t len, cap;
> };
That approach would have incurred a 12-byte overhead for each string or
vector on a PDP-11 - that would have been a substantial disincentive on
a memory-constrained system.
And none of that stops some programmer from doing
slice.cap=255 - or is
it read-only? ;)
Slices and strings are built-in types in Go. They can be modelled as the
above structure but that is an implementation detail. It is possible to
reduce the capacity of a slice (but not a string) but attempting to
increase it will result in a runtime exception ("panic" in Go speak).
--
Peter Jeremy