countUntil with negated pre-defined predicate?

[Harry Gillanders]

On Saturday, 2 May 2020 at 18:23:30 UTC, Robert M. Münch wrote:
> Or is there an even better way to search for all "drawable 
> unicode characters"?

This depends on what you classify as drawable, and what you 
consider to be a character (the joys of Unicode), and why you 
want to search for them anyway.

One way (I haven't verified this) could be to check if any of the 
code-points within a grapheme are graphical[1], and not 
white-space (and are not any other code-point you consider 
non-drawable).

Which could look like so:

	import std.algorithm;
	import std.range;
	import std.uni;

	size_t drawableCharacterCount (CodePoints) (auto ref CodePoints 
codePoints)
	if (isInputRange!CodePoints && is(ElementType!CodePoints : 
dchar))
	{
		bool isDrawableCodePoint (dchar c)
		{
			return c.isGraphical() && !c.isWhite();
		}

		return codePoints.byGrapheme().count!(
			g => g[].any!isDrawableCodePoint
		);
	}

[1]: 
https://www.unicode.org/versions/Unicode13.0.0/ch02.pdf#G286941

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