# What's New -  May, 2010

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May 3, 2010:  I been busy cutting next winter's firewood for the past week, but it's raining today so I'll post a new Beginners program in our Delphi techniques section:  "Twofer" is the slang expression meaning two for the price of one.  Our Twofers program solves two problems that I ran across on two consecutive days and each problem has exactly two solutions.

May 11, 2010:  My Logic Problem Solver program is probably one of the 3  or 4 most complex programs on DFF (along with CutList, Roller Coaster, and Word Stuff).  It is also the least downloaded of the 4, but "different strokes for different folks" as they say.  I still enjoyed the challenge of writing it.  A minor update, Logic Problem Solver (Version 3.1),  was posted today to clarify and correct some spelling errors in the descriptive text, enlarge text size for these old eyes , and convert references to DelphiForFun.org into live hyperlinks.

May 25, 2010: Catalan numbers were discovered by Euler when he went looking for the number of ways that an N-sided convex polygon could be divided into triangles by drawing non-intersecting diagonals. A more recent interpretation notes that this is also the number of simultaneous handshakes between guests at a circular table that can occur without any arm crossing another guest's arm.  In 1838 mathematician Eugene Catalan documented the same series (shifted by a couple of positions) as the number of ways that an expression with N +1 variables and connected by binary operators could be parenthesized.  Today's Catalan Numbers program in the Math Topics sections presents a program which not only calculates the Catalan number for expressions with a given number of variables, but also enumerates and lists all possible expressions.

May 31, 2010:  A recent London Times "mathematical" crossword puzzle posed a problem involving "almost" pandigital numbers (numbers containing digits 1 through 9 exactly once).   To help a viewer solve the puzzle, Problem #6 was added to our Pandigitals program, Version 3.1  which was posted today.