Monthly Archives: January 2011

Inputs are contravariant….

Inputs are contravariant, outputs are covariant and input-outputs are invariant.”Sounds erudite but what does it really mean. Well the concept is not new. My first introduction to the concept was from the VDM book by C.B.Jones where it is referred … Continue reading

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“Serial Number”

Here is a puzzle that NPR broadcast in November 2010. What two world capitals can be found by rearranging the letters in the phrase “serial number.” Being the programmer I claim to be, I wanted to write a program that … Continue reading

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