l03_6up - : Expressions: Recap : CSci 1113 C/C+ for...

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: CSci 1113 C/C++ for Scientists and Engineers Section 010 - evening class Boolean Expressions and Flow of Control Prof. Eric Van Wyk and Ted Kaminski Spring 2010 c ± Van Wyk and Kaminski CSci 1113: C/C++ for Scientists and Engineers, evening class Spring 2010 Page 1 / 35 Expressions: Recap : Exercise 3.1 Consider the following: double d; int m, n; d = m / n ; How many different ways can you modify the above code so that d gets the value of m divided by n using floating point division instead of integer division. c ± Van Wyk and Kaminski CSci 1113: C/C++ for Scientists and Engineers, evening class Spring 2010 Page 1 / 35 Expressions: Recap : Expressions: Recap I static cast: there are others that we will come to later I Additional modifiers: short , unsigned e.g. short int x; e.g. unsigned int y; c ± Van Wyk and Kaminski CSci 1113: C/C++ for Scientists and Engineers, evening class Spring 2010 Page 2 / 35 Expressions: Recap : Representing integers I How should we represent negative integers? I Consider Two’s complement: I a single representation for 0 c ± Van Wyk and Kaminski CSci 1113: C/C++ for Scientists and Engineers, evening class Spring 2010 Page 3 / 35 Boolean Expressions : Consider the following problem: I The City of Minneapolis needs to issue health warning if the air pollution rises to a dangerous level. I Pollution measurements are taken in several locations and measured in “number of pollutant parts per million’. An average is computed and a health warning is raised if that average is over 50 parts per million. I We know how to compute averages, but do not know how to make decisions based on such calculations. I We need to compute “boolean values” - values of True or False. c ± Van Wyk and Kaminski CSci 1113: C/C++ for Scientists and Engineers, evening class Spring 2010 Page 4 / 35 Boolean Expressions : Boolean? I Where does the work “boolean” come from? I George Boole - an English mathematician who discovered a logic of true/false values. I This logic is part of the foundation of computer science. c ± Van Wyk and Kaminski CSci 1113: C/C++ for Scientists and Engineers, evening class Spring 2010 Page 5 / 35
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Boolean Expressions : From the perspective of type systems . .. I We need a type for the boolean values “true” and “false”. I In C++ this type is written bool and the literals are written true and false . I What operators should we have? c ± Van Wyk and Kaminski CSci 1113: C/C++ for Scientists and Engineers, evening class Spring 2010 Page 6 / 35 Boolean Expressions Boolean Operators: Operators I Relational operators: < , , > , , =, 6 = I Logical operators: (“and”), (“or”), ¬ (“not”) I In C++ these are: < , <= , > , >= , == , != .
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l03_6up - : Expressions: Recap : CSci 1113 C/C+ for...

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