Access to column number

[binarycow]

Does RCParsing support making decisions based on the column number?

Consider an example language that supports multi-line strings:

description "This is a multi-line string.
             
             The column number of the initial double-quote is remembered.
             For each line that follows, up to that number of leading
             spaces are trimmed";

☝️ is equivalent to the following:

This is a multi-line string.
             
The column number of the initial double-quote is remembered.
For each line that follows, up to that number of leading
spaces are trimmed

Another example:

         "Foo
          bar"

is equivalent to Foo\nbar

[RomeCore]

No, it's not supported natively, but in your example it can be easily done via Custom tokens, there is simplified example how to do it:

builder.CreateToken("Multiline_Str")
	.Literal('"')
	.Custom((CustomTokenPattern self, string input, int start, int end) =>
	{
		// Count the column number
		int column = 0;
		int colStart = start - 1;

		while (colStart >= 0 && input[colStart] != '\n' && input[colStart] != '\r')
		{
			colStart--;
			column++;
		}

		var sb = new StringBuilder();
		int pos = start;
		bool trimming = false;
		int lastNewlinePos = start;

		while (pos < end && input[pos] != '"')
		{
			// The logic
			
			// ...
			
			// If column number less than expected -> fail
			if (currentColumn < column && !char.IsWhiteSpace(input[pos]))
				return ParsedElement.Fail;
		}

		return new ParsedElement(start, pos - start, intermediateValue: sb.ToString());
	})
	.Literal('"')
	
	.Pass(index: 1); // Pass intermediate value of child Custom token up

Also, when using barrier tokens in your parser, you may want to disable them for strings:

builder.CreateToken("Multiline_Str")
	...
	.Configure(c => c.IgnoreBarriers());

[RomeCore]

I also got idea about API for column calculation:

builder.CreateToken("Multiline_Str")
	.Literal('"')
	.Custom((CustomTokenPattern self, string input, int start, int end) =>
	{
		// Get the column number
		int column = self.GetColumnNumber(input, start);
		
		// ...
	})
	.Literal('"');