-----Original Message----- From: boost-bounces@lists.boost.org [mailto:boost-bounces@lists.boost.org] On Behalf Of Phil Endecott Sent: 12 February 2009 14:13 To: boost@lists.boost.org Subject: Re: [boost] Review Request: Introduction of boost::string namespace Re: Review Request: Introduction of boost::string namespace
Stewart, Robert wrote:
From: Phil Endecott
What do people think about the string/number conversions in N2408 ? (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2408.html - what is the status of that?) Unless there's something wrong with that, I think we should build on it rather than re-inventing the wheel.
Those are C-style. The advantage of a template is that the compiler deduces the correct implementation.
The compiler can also deduce the correct implementation using overloading, which is what N2408 proposes for its to_string functions:
string to_string(long long val); string to_string(unsigned long long val); string to_string(long double val);
For the from_string functionality we hit the standard problem that we can't type match on the type of the thing that the result is being assigned to:
short a = from_string(s); float f = from_string(s);
The compiler can't deduce the correct implementation; we have to tell it (unless we pass the result by reference I suppose). We have a choice of template syntax:
short a = from_string<short>(s); float f = from_string<float>(s);
or the "C like" syntax proposed by N2408 (which I've just noticed doesn't mention short anywhere, breaking my example):
int i = stoi(s); float f = stof(s);
In terms of syntax the latter is clearly more concise; some might argue that it's too concise (i.e. cryptic), but I would say that these conversions and their C equivalents are sufficiently commonly used that users will quickly learn what they do. But apart from these syntax differences, are there any benefits to one version rather than the other?
What about handling user-defined types like big integer and big floating point like NTL ZZ, quad_float, RR, and GMP equivalents? Hardware is unlikely to go beyond 128 bit FP or int, if that, so we need to think ahead about more accurate integer and floating-point types in software. Only the to_string and from_string apply here? NTL uses the ugly RR v; v = to_RR("12345.6789"); but v = from_string<RR>("12345.6789"); feels better. Views? Paul --- Paul A. Bristow Prizet Farmhouse Kendal, UK LA8 8AB +44 1539 561830, mobile +44 7714330204 pbristow@hetp.u-net.com