Steven Pinker -- How the Mind Works - Hampshire High Italian ...

Thinking Machines 91ual, The Elements of Style). They give advice on what makes a programwork powerfully, run efficiently, and evolve gracefully. One of their maximsis "Replace repetitive expressions by calls to a common function."For example, if a program has to compute the areas of three triangles, itshould not have three different commands, each with the coordinates ofone of the triangles embedded in its own copy of the formula for the areaof a triangle. Instead, the program should have the formula spelled outonce. There should be a "calculate-triangle-area" function, and it shouldhave slots labeled X, Y, and Z that can stand for any triangle's coordinates.That function can be invoked three times, with the coordinatesfrom the input plugged into the X, Y, and Z slots. This design principlebecomes even more important as the function grows from a one-line formulato a multistep subroutine, and it inspired these related maxims, allof which seem to have been followed by natural selection as it designedour modular, multiformat minds:Modularize.Use subroutines.Each module should do one thing well.Make sure every module hides something.Localize input and output in subroutines.A second principle is captured in the maximChoose the data representation that makes the program simple.Kernighan and Plauger give the example of a program that reads in a lineof text and then has to print it out centered within a border. The line oftext could be stored in many formats (as a string of characters, a list ofcoordinates, and so on), but one format makes the centering child's play:allocate eighty consecutive memory slots that mirror the eighty positionsin the input-output display. The centering can be accomplished in a fewsteps, without error, for an input of any size; with any other format, theprogram would have to be more complicated. Presumably the distinctformats of representation used by the human mind—images, phonologicalloops, hierarchical trees, mentalese—evolved because they allowsimple programs (that is, stupid demons or homunculi) to compute usefulthings from them.And if you like the intellectual stratosphere in which "complex systems"of all kinds are lumped together, you might be receptive to Herbert