Implementing an "in" operator

"Ed Davis" <ed_davis2@yahoo.com>13 Nov 2002 12:23:05 -0500

From comp.compilers

Related articles
Implementing an "in" operator ed_davis2@yahoo.com (Ed Davis) (2002-11-13)
Re: Implementing an "in" operator n502640813.ch@chch.demon.co.uk (Charles Bryant) (2002-11-20)
Re: Implementing an "in" operator sos@zjod.net (Steve Siegfried) (2002-11-24)
Re: Implementing an "in" operator ed_davis2@yahoo.com (Ed Davis) (2002-11-26)
| List of all articles for this month |

 From: "Ed Davis" Newsgroups: comp.compilers Date: 13 Nov 2002 12:23:05 -0500 Organization: http://groups.google.com/ Keywords: code, question, comment Posted-Date: 13 Nov 2002 12:23:05 EST

Any ideas on how one would implement an "in" operator?

As in (no pun intended):

if (a in b,c,d..e)
statements;

translates to:

if (a == b or a == c or (a >= d and a <=e))
statements;

I don't have a problem with unary and binary operators, but
this one has got me stumped. Part of my simple
(integer-only) expression parser is shown below:

static Tree *expr(int p) {
Tree *t = primary(); /* also handles unary operators */
while (isBinaryOperator(tok.sym) &&
precedence(tok.sym) >= p) {
const Symtype op = tok.sym;
getsym();
t = mkBinaryNode(op, t,
expr(associativity(op) == Right ?
precedence(op) : 1 + precedence(op)));
}
return t;
}

Any ideas on how "in" might be implemented in the above?
[Treat comma and .. as operators long enough to build up a tree of
stuff you can translate when you deal with the "in", perhaps. -John]

Post a followup to this message