6 replies to this topic

[Reedbeta]

I wrote an article about an algorithm that doesn't seem to be very widely known, but should be! It's called the "shunting-yard algorithm" and is used to parse arithmetic expressions in infix notation. Check out the article here: http://www.reedbeta....yard-algorithm/

[}:+()___ (Smile)]

Ha ha, for my parsers I've reinvented the wheel and created modification of this algorithm with combined operand/operation stack. In my stack I have operands (A) or operands with incomplete operation (A+). Each stack element have 'level' which corresponds to operator precedence and incoming operator combines stack elements with level higher than operator level. At the end of expression I put dummy operator with lowest level.

For example, parsing token sequence A * B + C * D [end]

A
A*
A*   B
(A*B)+		   <-  A* and B have higher level than +
(A*B)+   C
(A*B)+   C*
(A*B)+   C*   D
((A*B)+(C*D))=	   <-  (A*B)+, C* and D have higher level than [end]

If someone decides to use my version instead of original I can give additional details.

[roel]

That was an interesting read, Reed. Haven't heard of it in CS classes either.

[fireside]

I think, particularly with indy games, these kinds of solutions may be used more often.

[Stainless]

Interesting, quick and simple to code as well

However I still just "Use the Forth Luke"

You can write a Forth interpreter in very little code

[.oisyn]

Ah yes, one of the legacies of the famous Dutch computer scientiest Edsger Dijkstra

.edit:

Quote

I never heard of this algorithm until I happened to see a forum post that referenced it

Funny, was it this one? http://devmaster.net...dpost__p__65660

[Reedbeta]

Yes, .oisyn, that was indeed the one.