Expressions, and Arithmetic

9/9/2012

For Next Time

 Read Chapter 4 Expressions, and Arithmetic

Chapters 4

1 2

Arithmetic Operator Precedence

 Just as in normal mathematics:

Operator Operation  * and / are applied before + and – + Addition  Parentheses can override the order of application - Subtraction * Multiplication / Division % Modulus

Operator Associativity Operator Arity

 Is x + y + z evaluated as  Unary:  (x + y) + z  -x

 x + (y + z)  +sum

 Does it matter?  Binary  sum + diff

 2 - ev

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Precedence and Associativity Mixed Arithmetic

 In an expression involving different numeric Precedence from high to low types, the less dominant types are converted to the more dominant types for the purpose of Arity Operators Associativity evaluating the expression Unary +, -  Example Binary *, /, % Left Binary +, - Left int x = 5; Binary = Right double y = 4.0, z; z = x + y;

Comments Source Code Formatting

 Helpful to human readers  Like comments: unimportant to compiler but  Ignored by the compiler very important to human readers  Single-line comments  Some guidelines: // This is a brief note  Each statement on its own line  Block comments  Align curly braces in a standard way /* This is a longer remark  Indent bodies of functions and structured that covers statements several lines. */  Use spaces around binary operators

Errors Logic Errors

 Compile-time errors  Not detectable by the compiler

 Violation of the rules of the C++ language  Not detectable by the run-time environment  Compiler tells you about them  The program’s logic is not correct

 Plentiful when you are first learning a language  The hardest kinds of errors to diagnose and repair

 Generally easy to fix  The compile can provide no feedback

 Runtime errors  Can result from carelessness, lack of understanding of the problem, lack of understanding of the way the  Depends on the situation of the running program: like dividing by a variable that has been assigned zero language works; for example:  Wrote x - y, meant y - x  The run-time environment terminates the program’s execution

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Logic Error? Additional Arithmetic Operators

 Increment: ++  Decrement: --  Increase: += double degrees_F, degrees_C;  Other operations similar to increase:  -= cin >> degrees_F;  *= degrees_C = 5/9*(degrees_F - 32);  /=  %=

 Others . . .

Next . . .

Conditional execution