metastrings.d

// Written in the D programming language.

/**
Templates with which to do compile-time manipulation of strings.

Macros:
 WIKI = Phobos/StdMetastrings

Copyright: Copyright Digital Mars 2007 - 2009.
License:   <a href="http://www.boost.org/LICENSE_1_0.txt">Boost License 1.0</a>.
Authors:   $(WEB digitalmars.com, Walter Bright),
           Don Clugston
Source:    $(PHOBOSSRC std/_metastrings.d)
*/
/*
         Copyright Digital Mars 2007 - 2009.
Distributed under the Boost Software License, Version 1.0.
   (See accompanying file LICENSE_1_0.txt or copy at
         http://www.boost.org/LICENSE_1_0.txt)
 */
module std.metastrings;

/**
Formats constants into a string at compile time.  Analogous to $(XREF
string,format).

Parameters:

A = tuple of constants, which can be strings, characters, or integral
    values.

Formats:
 *    The formats supported are %s for strings, and %%
 *    for the % character.
Example:
---
import std.metastrings;
import std.stdio;

void main()
{
  string s = Format!("Arg %s = %s", "foo", 27);
  writefln(s); // "Arg foo = 27"
}
 * ---
 */

template Format(A...)
{
    static if (A.length == 0)
        enum Format = "";
    else static if (is(typeof(A[0]) : const(char)[]))
        enum Format = FormatString!(A[0], A[1..$]);
    else
        enum Format = toStringNow!(A[0]) ~ Format!(A[1..$]);
}

template FormatString(const(char)[] F, A...)
{
    static if (F.length == 0)
        enum FormatString = Format!(A);
    else static if (F.length == 1)
        enum FormatString = F[0] ~ Format!(A);
    else static if (F[0..2] == "%s")
        enum FormatString
            = toStringNow!(A[0]) ~ FormatString!(F[2..$],A[1..$]);
    else static if (F[0..2] == "%%")
        enum FormatString = "%" ~ FormatString!(F[2..$],A);
    else
    {
        static assert(F[0] != '%', "unrecognized format %" ~ F[1]);
        enum FormatString = F[0] ~ FormatString!(F[1..$],A);
    }
}

unittest
{
    auto s = Format!("hel%slo", "world", -138, 'c', true);
    assert(s == "helworldlo-138ctrue", "[" ~ s ~ "]");
}

/**
 * Convert constant argument to a string.
 */

template toStringNow(ulong v)
{
    static if (v < 10)
        enum toStringNow = "" ~ cast(char)(v + '0');
    else
        enum toStringNow = toStringNow!(v / 10) ~ toStringNow!(v % 10);
}

unittest
{
    static assert(toStringNow!(1uL << 62) == "4611686018427387904");
}

/// ditto
template toStringNow(long v)
{
    static if (v < 0)
        enum toStringNow = "-" ~ toStringNow!(cast(ulong) -v);
    else
        enum toStringNow = toStringNow!(cast(ulong) v);
}

unittest
{
    static assert(toStringNow!(0x100000000) == "4294967296");
    static assert(toStringNow!(-138L) == "-138");
}

/// ditto
template toStringNow(uint U)
{
    enum toStringNow = toStringNow!(cast(ulong)U);
}

/// ditto
template toStringNow(int I)
{
    enum toStringNow = toStringNow!(cast(long)I);
}

/// ditto
template toStringNow(bool B)
{
    enum toStringNow = B ? "true" : "false";
}

/// ditto
template toStringNow(string S)
{
    enum toStringNow = S;
}

/// ditto
template toStringNow(char C)
{
    enum toStringNow = "" ~ C;
}


/********
 * Parse unsigned integer literal from the start of string s.
 * returns:
 *    .value = the integer literal as a string,
 *    .rest = the string following the integer literal
 * Otherwise:
 *    .value = null,
 *    .rest = s
 */

template parseUinteger(const(char)[] s)
{
    static if (s.length == 0)
    {
        enum value = "";
        enum rest = "";
    }
    else static if (s[0] >= '0' && s[0] <= '9')
    {
        enum value = s[0] ~ parseUinteger!(s[1..$]).value;
        enum rest = parseUinteger!(s[1..$]).rest;
    }
    else
    {
        enum value = "";
        enum rest = s;
    }
}

/********
Parse integer literal optionally preceded by $(D '-') from the start
of string $(D s).

Returns:
   .value = the integer literal as a string,
   .rest = the string following the integer literal

Otherwise:
   .value = null,
   .rest = s
*/

template parseInteger(const(char)[] s)
{
    static if (s.length == 0)
    {
        enum value = "";
        enum rest = "";
    }
    else static if (s[0] >= '0' && s[0] <= '9')
    {
        enum value = s[0] ~ parseUinteger!(s[1..$]).value;
        enum rest = parseUinteger!(s[1..$]).rest;
    }
    else static if (s.length >= 2 &&
            s[0] == '-' && s[1] >= '0' && s[1] <= '9')
    {
        enum value = s[0..2] ~ parseUinteger!(s[2..$]).value;
        enum rest = parseUinteger!(s[2..$]).rest;
    }
    else
    {
        enum value = "";
        enum rest = s;
    }
}

unittest
{
    assert(parseUinteger!("1234abc").value == "1234");
    assert(parseUinteger!("1234abc").rest == "abc");
    assert(parseInteger!("-1234abc").value == "-1234");
    assert(parseInteger!("-1234abc").rest == "abc");
}