Re: Unquoted strings in BASIC

On Tue, 3 Dec 2024 17:57:13 +0100
Hans =C5berg <[email protected]> wrote:

> In general, one tries to exploit tokens to do special things, which
> is also useful in a Bison parser when adding mid-rule actions.

That's good advice, hard-won.  =20

> > it seems it is much easier to parse everything in the data section
> > as a string

I think you mean to lex each element in the DATA line, removing the
quotes, but not distinguish between number and string?  IIUC that will
work fine.  Those elements don't *have* a type until they're assigned
to a variable; until then, they're just data, just as is true for
any other kind of input. =20

It occurs to me you could have an exclusive start condition that could
look like this:

	DATA[[:blank:]]+{ yy_push_state(data); ... }

	<data>{
	["][^"]*["] |
	['][^']*['] { /* use yytext +1, minus trailing quote */ }
	[,]$   { /* return empty string */ }
	[,]/[,] { /* return empty string */ }
	[,]=20
	[^,\r\n]+ { return yytext as string */
	[\r]?[\n]  { yy_pop_state(); }
	}

There is a difficulty: an erroneous DATA line.  You have to allow for
missing closing quotes e.g.,=20

	DATA "hello,2

That means you needs patterns like

	["][^"]*$ { return ERROR_TOKEN; }

to tell the parser the DATA is borked. =20

We have certainly flogged this horse good and well.  I hope it's been
helpful and that your BASIC interpreter soldiers on. =20

--jkl