Re: Compile Time String processing

From:

Walter Bright <walter@digitalmars-nospamm.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Fri, 23 Feb 2007 03:37:39 CST

Message-ID:

<s8idnZVYaIzvgkPYnZ2dnUVZ_t2tnZ2d@comcast.com>

wes wrote:

Right now I'm trying to figure out is if string processing is even
possible at compile time using templates. So far after much searching
I've only found numeric operations in the metaprogramming examples and
no string examples and I'm wondering if this is for a reason i.e. that
C++ can't process strings in this way. Any ideas?

C++ can't do it because string literals cannot be passed as template
arguments (see C++98 14.3.2). However, since string literals can be
passed as template arguments in the D programming language, one could
write a string hashing template as:

template hash(char [] s, uint sofar=0)
{
    static if (s.length == 0)
       const hash = sofar;
    else
       const hash = hash!(s[1 .. length], sofar * 11 + s[0]);
}

uint foo()
{
     return hash!("hello world");
}

Walter Bright
www.digitalmars.com
C, C++, D programming language compilers

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