End Of Line character and others not working.

[H. S. Teoh]

On Sat, Aug 17, 2013 at 07:19:19AM +0200, Alan wrote:
> On Saturday, 17 August 2013 at 05:05:12 UTC, H. S. Teoh wrote:
> >On Sat, Aug 17, 2013 at 06:53:16AM +0200, Alan wrote:
> >>Hello!  The past few hours I've been working on some things and I
> >>came accross a small bug.
> >>
> >>I'm essentially practicing lexing and parsing by implementing a
> >>(very) simple language.  Everything is going great so far (variable
> >>declarations, writing to stdout etc...) but I have a small problem
> >>with my string literals.  I've got them working fine, quotes can be
> >>escaped etc... But when they include the new line character (\n) for
> >>example and it's written out it doesn't create a new line but prints
> >>out those characters raw.  Does anyone have any idea why?  Any help
> >>is very much appreciated!
> >
> >Which quotation marks did you use for your string literals?
> >
> >If you use double quotes, then it should work: "\n"
> >
> >But if you use the other quoting syntaxes, the \n may be treated
> >literally rather than as an escape sequence, e.g., `\n` is a string
> >of two characters '\' and 'n'.
> >
> >
> >T
> 
> I don't think it matters how my string literals are recoginized,
> they can be recognized by double or single quotes.
> Either way the value is stored in a string then written out, but \n
> is written out raw for some reason.

Wait, are you talking about the language that you're parsing having
string literals that contain "\n"? If so, then you need to manually
translate them, since in the input file, they are two literal character
'\' and 'n', and the computer wouldn't know how you want to interpret
them. So you have to do something like this:

	auto parseStringLiteral(R)(R input)
		if (is(ElementType!R : dchar))
	{
		auto value = appender!string();
		while (!input.empty && input.front != '\"')
		{
			// Interpret escape sequences here
			if (input.front == '\\') {
				input.popFront();
				if (input.empty)
					throw new Exception("Unterminated escape sequence");

				switch(input.front) {
				case 'n':
					app.put("\n");
					break;
				// ... put whatever other escapes you
				// want to interpret here
				}
			} else {
				// Not an escape sequence, transcribe to
				// output literally.
				app.put(input.front);
			}
		}
		return value.data;
	}

In other words, none of the escape sequences are implemented for you;
you have to implement them yourself.


T

-- 
"You are a very disagreeable person." "NO."