Modeling and Reasoning about Computation : Theory and Applications of Automata , Languages , Undecidability , BDD , SAT , and SMT Methods through Declarative Programming

ly, the print command looks like this: print(<< a separator >>.join(map(str, list_of_things)) + "\t\t" + << a tail string >>) For example, print(" :-) ".join(map(str, [{’a’}, 10, {’a’:10}, {1:20}, []])) + " " + " (-: ") produces {’a’} :-) 10 :-) {’a’: 10} :-) {1: 20} :-) [] (-: The cool thing is that the format modifier function applied to strings formats the string in a given way (much like Unix’s sprintf). URL http://www. shocksolution.com/2011/11/python-string-format-examples/ gives a very nice set of examples to explain this. Let me present this through some examples. 16CHAPTER 2. A BRIEF TOUR OF PYTHON, DECLARATIVE PROGRAMMING • Suppose for some crazy reason, you want to print natural numbers 10 through 50 in decimal as follows: 10, 20, 30, 40, 50 This is achieved through: "{0:1d}, {1:2d}, {2:4d}, {3:8d}, {4:16d}".format(10,20,30,40,50)} • You can now print these numbers in binary, as as follows: 1010, 10100, 11110, 101000, 110010 through "{0:1b}, {1:2b}, {2:4b}, {3:8b}, {4:16b}".format(10,20,30,40,50) • Now obtain a, 14, 1e, 28, 32 through "{0:1x}, {1:2x}, {2:4x}, {3:8x}, {4:16x}".format(10,20,30,40,50) • Suppose x be variable in a program you have, and say x = 0.1234567890. • Suppose you are faced with printing this: ’sin(0.1234567890) = 1.2314e-01’. but you want things to be rounded up to 4 places, meaning 0.1234567890 must appear as 0.1235. • You can generate this entire string by doing this: "sin({0:.4f}) = {1:.4e}".format(0.1234567890, sin(0.123456789)) 2.1.9 Making a formatter function through a Lambda Here is an interesting example putting these ideas together: fm = lambda x: ’{0:3d}’.format(x) # each item is the "zeroth" item, hence "0:" list(map(fm, [1,2,30,400]))