Hi,

Please watch: https://youtu.be/siw602gzPaU

If he had learned this method like me, he would not have needed if's and long explanations. :)

It's a very redundant thing (ASCII magic) that also weeds out the incompatible character set. This approach adopts the toggle/flip method through XOR rather than toLower/toUpper:

import std.traits : isNarrowString;
bool isAsciiString(T)(T str)
if (isNarrowString!T)
{
  import std.uni : byGrapheme;
  auto range = str.byGrapheme;

  import std.range : walkLength;
  return range.walkLength == str.length;
}

auto toggleCase(T)(T str)
in (str.isAsciiString, "Incompatible character set!")
{
  auto ret = str.dup;
  foreach (ref chr; ret) {
    chr ^= ' '; // toggle character
  }
  return ret;
}

import std.stdio;
void main()
{
  string test = "dlANG"; // "ḍlANG";

  test.toggleCase().writeln(); // "DLang"
}

SDB@79

On Sunday, 13 April 2025 at 17:28:12 UTC, Salih Dincer wrote:

This is clever, but you are still missing something important. Take a look at this example:

string test = "I love dlang!";
test.toggleCase().writeln(); // "iLOVEDLANG" - wrong!

On Sunday, 13 April 2025 at 17:28:12 UTC, Salih Dincer wrote:

Again and wgain opss! You can't get rid of if, but it's better with isAlpha(), like?

auto toggleCase(T)(T str)
in (str.isAsciiString, "Incompatible character set!")
{
  import std.ascii : isAlpha;
  auto ret = str.dup;
  foreach (ref chr; ret)
  {
    if (chr.isAlpha)
    {
      chr ^= ' '; // toggle character
    }
  }
  return ret;
}

unittest
{
  string Aqw12 = `aQW
 12`;
  assert(Aqw12.toggleCase() == "Aqw\n 12");
}

SDB@79