• Don Clugston (17/17) Apr 13 2007 In std.metastring there are functions to convert integers to strings at
• Walter Bright (2/4) Apr 13 2007 Can these be replaced with .stringof ?
• Don Clugston (3/8) Apr 13 2007 Yup. It should probably be wrapped in a deprecated{} now. As should
• Don Clugston (11/19) Apr 13 2007 For example:
• Walter Bright (2/14) Apr 13 2007 I think AST macros should take care of this problem.

Don Clugston <dac nospam.com.au> writes:

In std.metastring there are functions to convert integers to strings at 
compile time, but none to go the other way.
Floating point conversions are the worst; there are so many different 
formats, worrying about round-off error, etc. It's a total nightmare.
Luckily, this works...
<g>

/// Converts 'str' into a constant of type T.
/// str may contain any D expression which evaluates to a literal.
T evaluateLiteral(T, char [] str)()
{
     mixin("return " ~ str ~ ";"\n);
}

// Examples:
static assert(evaluateLiteral!(real, "1.234e-56") == 1.234e-56);
static assert(evaluateLiteral!(cdouble, "(8.45+56i)*36.2i") == 
(8.45+56i)*36.2i);
static assert(evaluateLiteral!(char [], `"abc"[1..2] ~ "def"`) == "bdef");

Walter Bright <newshound1 digitalmars.com> writes:

Don Clugston wrote:
 In std.metastring there are functions to convert integers to strings at 
 compile time,

Can these be replaced with .stringof ?

Don Clugston <dac nospam.com.au> writes:

Walter Bright wrote:
 Don Clugston wrote:
 In std.metastring there are functions to convert integers to strings 
 at compile time,

 
 Can these be replaced with .stringof ?

Yup. It should probably be wrapped in a deprecated{} now. As should 
std.math2.

Don Clugston <dac nospam.com.au> writes:

Don Clugston wrote:
 Walter Bright wrote:
 Don Clugston wrote:
 In std.metastring there are functions to convert integers to strings 
 at compile time,

 Can these be replaced with .stringof ?

 Yup. It should probably be wrapped in a deprecated{} now. As should 
 std.math2.

For example:

template toString(real x)
{
     const char [] toString=x.stringof;
}

Unfortunately, none of these work inside a CTFE function. The problem 
is, that a CTFE function has to also work at runtime, and so it can't 
use compile-time variables in template value arguments (and it can't 
index tuples, etc). These kinds of operations are the only ones where 
template metaprogramming still survives.

Walter Bright <newshound1 digitalmars.com> writes:

Don Clugston wrote:
 For example:
 
 template toString(real x)
 {
     const char [] toString=x.stringof;
 }
 
 Unfortunately, none of these work inside a CTFE function. The problem 
 is, that a CTFE function has to also work at runtime, and so it can't 
 use compile-time variables in template value arguments (and it can't 
 index tuples, etc). These kinds of operations are the only ones where 
 template metaprogramming still survives.

I think AST macros should take care of this problem.