Thoughts about D

[Walter Bright]

On 11/26/2017 9:11 PM, Neia Neutuladh wrote:
> The culprit for the C# version's poor performance was System.String.Substring, 
> which allocates a copy of its input data. So "Hello world".Substring(5) creates 
> a new char* pointing at a new memory allocation containing "Hello\0". C++'s 
> std::string does the same thing. So if I reimplemented subtex naively in C++, 
> its performance would be closer to the C# version than to the D version.
> 
> I could probably get slightly better performance than the D version by writing a 
> special `stringslice` struct. But that's a lot of work, and it's currently just 
> barely fast enough that I realize that I've actually run the command instead of 
> my shell inexplicably swallowing it.

0 terminated strings in C (and C++) have always been a severe performance issue 
for programs that deal a lot in strings, for these reasons:

1. To get a substring, a copy must be made, meaning also that storage allocated 
and managed for it.

2. To do most operations on it, you need to do a strlen() or equivalent.

You can always write your own string package to deal with, and I've written many 
:-( and they all failed for one reason or another, mostly because about 
everything in the C/C++ ecosystem is built around 0 terminated strings.