Expressions and Arithmetic Chapters 4 1 2 CPTR 124 Checklist - PDF document

1/28/2011 For Next Time  Read Chapter 4 Expressions and Arithmetic Chapters 4 1 2 CPTR 124 Checklist Type Conversions  Read the appropriate chapter(s)  Re-read the appropriate chapter(s)  int  double, is this OK  Download the code we develop in class  double  int, is this OK?  Experiment with the class code  Start working on the next lab  Visit the tutors if necessary  Check WebGrades periodically 4 Data Ranges Arithmetic Operator Operation + Addition - Subtraction * Multiplication / Division % Modulus 7 1

1/28/2011 Operator Precedence Operator Associativity  Is x + y + z evaluated as  Just as in normal mathematics:  * and / are applied before + and –  (x + y) + z  Parentheses can override the order of application  x + (y + z)  Does it matter? Operator Arity Precedence and Associativity  Unary: Precedence from high to low  -x  +sum Arity Operators Associativity  Binary +, - Unary  sum + diff Binary *, /, % Left  2 - ev +, - Binary Left Binary = Right Mixed Arithmetic Comments  In an expression involving different numeric  Helpful to human readers types, the less dominant types are converted  Ignored by the compiler to the more dominant types for the purpose of  Single-line comments evaluating the expression // This is a brief note  Example  Block comments int x = 5; /* This is a longer remark double y = 4.0, z; that covers z = x + y; several lines. */ 2

1/28/2011 Source Code Formatting Errors  Like comments: unimportant to compiler but  Compile-time errors very important to human readers  Violation of the rules of the C# language  Compiler tells you about them  Some guidelines:  Plentiful when you are first learning a language  Each statement on its own line  Generally easy to fix  Align curly braces in a standard way  Runtime errors  Indent bodies of methods and structured  Depends on the situation of the running program: like statements dividing by a variable that has been assigned zero  Use spaces around binary operators  The run- time environment terminates the program’s execution Logic Errors Warnings  Not detectable by the compiler  Not a violation of the C# language  Not detectable by the run-time environment  Indicates that the programmer may be  The program’s logic is not correct making a mistake  The hardest kinds of errors to diagnose and repair  Indicates a potential logic error  The compile can provide no feedback  Do not prevent the compiler from producing  Can result from carelessness, lack of understanding of the problem, lack of understanding of the way the executable code language works; for example:  Example:  Wrote x - y , meant y - x  Declaring a variable but not using it Logic Error? Additional Arithmetic Operators  Increment: ++  Decrement: --  Increase: +=  Other operations similar to increase: double degrees_F, degrees_C;  -= degrees_F = double.Parse(Console.ReadLine());  *= degrees_C = 5/9*(degrees_F - 32);  /=  %=  Others . . . 3

1/28/2011 Next . . . Classes and objects 20 4