Talk:Prefix notation
From Wikipedia, the free encyclopedia
This stub is confusing. The notation for existential quantifier ($x)Gx does not seem to match the notation used in the artical.
Also, postfix notation redirects to Reverse Polish Notation
but Polish notation redirects to prefix notation.
I am tempted to fix this but the stub does not seem to say much on the general concept of prefix notation, and I don't think my maths is up to it.
-- Chris Q 09:39, 20 Nov 2003 (UTC)
Contents |
[edit] Merits
The following part of the article removed, for clarifications.
This was a piece from article:
- Polish notation is slightly easier to implement for computers, since the operation is encountered first, then the data to perform the operation comes later. However, people are much more familiar with infix notation.
This is a recent commment added by an anon into the article body:
- The "easier" part is simply not true, and the argumentation is arbitrary.
- Reverse Polish notation is, indeed, easier to implement, mainly because we are spared of the need for speculating about the order of operations. "Straight" Polish notation, however, is even a step-back from Infix notation with that respect, if we have to process it in natural (left-to-right) order.
- The ordering of operands with respect to the operation is of imaginary significance and is completely irrelevant to the ease of implementation "for computers." Note that what comes after the operation is not necessarily "data," but may be another prefix expression.
The remarks are of merit IMO. So, what are real advantages of this notation? See Reverse Polish Notation how they are presented. Mikkalai 19:59, 18 Mar 2005 (UTC)
- The point was that the original text was misleading, and was most probably due to confusion with RPN. PN is essentially isomorphic to RPN, and can be processed as such from right to left, thus leveraging the benefits of, but offering no advantages over, RPN.
- --AoS 14:51, 21 Mar 2005 (UTC)
Polish notation is also used for Symbolic Logic, in fact it was invented for this purpose. This fact is ignored in the article. I intend to correct this latter when I can get to my own computer.
[edit] Tcl
The note about this being used in Tcl is rather misleading. math in Tcl is in infix notation, but the language syntax is polish notation. Being this is a math article and when I first read the line, I became rather confused at what it meant. Could someone re-word this to read more clearly? I'm unsure how to word it myself. — Striker 22:48, 5 December 2005 (UTC)
[edit] Question about sentence
- The "conventional" notation did not become so until the 1970s and 80s.
Does this mean to say that "The (common OR currently used) notation did not become conventional until the 1970s and 80s." or somesuch? - Centrx 22:59, 21 May 2006 (UTC)
[edit] Tone
This page is written in a strange tone. I don't think it's good form to use the word "we" in an article (just as an example). Mo-Al 06:19, 25 June 2006 (UTC)
[edit] Polish notation for logic maybe wrong?
I believe that the D operator is not the "nand" (sheffer stroke) operator but the "dubious" operator, which is a unary operator:
Dx = ExNx
That is, when x is equivalent to not-x. This makes sense for the many-valued logics. (See C.I.Lewis and C.H. Langford's Symbolic Logic, (Dover Press, 1959), where they write about Łukasiewicz's 3-valued logic, Ł3.
-RR
[edit] Reference to Łukasiewicz Articles
A reference to an article by Łukasiewicz which introduces this system is needed. The notation is used in his works written in the 1920s, though I think that the standard is Elements of Mathematical Logic written 1929.
[edit] Is this a mistake?
The article reads : "Although obvious, it is important to note that the number of operands in an expression must equal the number of operators plus one, otherwise the statement makes no sense (assuming only binary operators are used in the expression). This can be easy to overlook when dealing with longer, more complicated expressions with several operators, so care must be taken to double check that an expression makes sense when using Polish notation."
I'm not sure I understand it, can someone please add an explanation or confirm if it's a mistake?
- It means that the number of things getting operated on is the number of operators + 1. For example, in "+ 1 2", "+" is the operator, and "1" and "2" are the operands. Mo-Al 02:40, 12 August 2006 (UTC)
[edit] In a more technically polish way
I'm reading this article, and towards the end it gives examples of association and distribution. For each it offers a more polish way of writing the statement of equivalence, using "=" as a binary operator.
I'm not sure that this use is appropriate, because it renders the equivalence confusing (and I have never seen this usage before... which does not mean it is incorrect, of course). Slightly Drunk 19:58, 4 January 2007 (UTC)
