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SIMPLE THINGS

Prime Numbers Revisited
by George Martin

Start ı Being Ardent ı An Example ı Sources and PDF

BEING ARDENT

What started this line of thinking and prompted me to write was the article "Algorithm Tests for Point Location" by Lawrence Arendt. [1] Arendt presents a simple way to determine if a point lies inside a triangle. I was impressed because I donıt usually come across software engineers who would consider this real-world geometry topic.

Most of us have probably written code for this type of testing. Iıve done it for rectangles and circles. Iıve said to myself, "This problem is trivial; you justı" and then I realized that my approach was like the second software reply from above. Lots of words, but no real substance and a long dark alley. Arendtıs triangle algorithm is a clever solution.

In his article, Arendt explains that, if you have a triangle ABC that has area A, then point X lies inside triangle ABC if the sum of the three triangles formed by point X and the three vertices equals the area A. So, if Area (ABX) + Area (AXC) + Area (XBC) = Area (ABC), then point X is inside triangle ABC. Draw yourself a picture and it should become clear.

Arendt used C++ to design and code his algorithm. I read that and was going to tell you how it would be much simpler to design and code in plain old C. So, I started to design and code a simpler version. To my surprise, I could do the design and coding in C, but it was not simpler.

The truth is that, in my original draft of this article, I went on to explain why C++ provided a better solution. I submitted it and then got an e-mail from Circuit Cellar Project Editor Dave Tweed (whose day job, ironically enough, is hardware engineering), who had proofread my manuscript. He showed me a simple C routine that was equivalent to the original C++ routine. Needless to say, I was flabbergasted that someone could come up with a solution that I couldnıt find.

Think again about seeking out the hardware experts for a good solution. I need to modify my observations and tell you that you may be surprised where you can get a clearer way of looking at your design problem. Be open to input from all sources, but be careful to weed out the signal from the noise.

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