Checking, whether string contains only ascii.

[H. S. Teoh via Digitalmars-d-learn]

On Wed, Feb 22, 2017 at 07:26:15PM +0000, berni via Digitalmars-d-learn wrote:
> In my program, I read a postscript file. Normal postscript files
> should only be composed of ascii characters, but one never knows what
> users give us.  Therefore I'd like to make sure that the string the
> program read is only made up of ascii characters. This simplifies the
> code thereafter, because I then can assume, that codeunit==codepoint.
> Is there a simple way to do so?
[...]

Hmm... What about:

	import std.range.primitives;

	bool isAsciiOnly(R)(R input)
		if (isInputRange!R && is(ElementType!R : dchar))
	{
		import std.algorithm.iteration : fold;
		return input.fold!((a, b) => a && b < 0x80)(true);
	}

	unittest
	{
		assert(isAsciiOnly("abcdefg"));
		assert(!isAsciiOnly("abcбвг"));
	}

Basically, it iterates over the string / range of characters and checks
that every character is less than 0x80, since anything that's 0x80 or
greater cannot be ASCII.


T

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