What are Operators? Some useful operators to get you started

What’s an Operator? Definition: An operator is a symbol that provides a shorthand way of telling your program to perform a computation or other type of action Unary operators: applied to a single variable or expression E.g., -y or j++ Binary operators: applied to two expressions E.g., x+y, x<y, x=y

Spreadsheet Example

Common Operators for Numbers Arithmetic +, -, *, / % gives remainder for integer division ++ (--) can be used to increment (decrement) values, and are unary operators Comparison == and != >, >=, <, <= Assignment = += (and -=, *=, /=) Negation (minus sign)

Numeric Examples

Assignment Issues Don’t mix up the assignment (=) and equality test (= =) operators Assignment moves RHS value into LHS variable LHS changes Equality test checks if LHS equals RHS Returns true if the are, false if not Neither side changes

Integer Division When integers are divided, the result is truncated 17/5  3 19/5  3 4/5  0 Remainders can be obtained with % (modulus) operator 17%5  2 19%5  4 4%5  4

Mixing Integers & Real Numbers Review: integers and real numbers have vastly different ranges of values Operations that mix integers and real numbers could exceed integer ranges Solution: Generally, when operators mix integers and real numbers, the values are “promoted” to real numbers before the operation takes place

Typecast C# will not let you assign values of one type to another type if it could cause problems—even if you “know” it is okay Typical example: assigning a double to an int int Test = 3.0; // will produce an error! Typecast operator: Unary operator puts the value type in parentheses in front of expression to eliminate warning int Test = (int)3.0; // Eliminates error Typecasts can also be used between compatible objects, as we’ll see later in the course

Typecast Example Notes: Only typecast when you are sure that you’ve got compatible types If they aren’t compatible (e.g., typecasting a negative number to an unsigned integer) the results will either be “unpredictable” or it will crash your program with an exception. Neither is good…

Common Operators for Strings Concatenation + “Hello” + “World” gives “HelloWorld” Comparison == and != These comparisons are case sensitive! Assignment = +=

string Operator Example Notes: Comparisons == and != test exact equality—they are case sensitive (like everything in C#) Because of case sensitivity, comparisons such as < and <= are not supported

Common Operators for Booleans Logical binary operators && : returns true if both sides are true || : returns true if either side is true Negation ! : Makes a true expression false or a false expression true Comparison == and != Conditional Boolean-expression ? Value1 : Value2 Assignment =

Conditional Operator Identical in usage to Excel =if( test, value-if-true, value-if-false) int X=17; int Y=12; string z=(X>Y) ? “X > Y” : “X <= Y”; int X=17; int Y=12; int z=(X>Y) ? X-Y : Y-X;

bool Operator Example

Parting words… Operators are generally intuitive once you start working with them Operators have “precedence” (e.g., * gets done before +) but use parentheses if there’s any doubt Remember that operators “return” a value Sometimes it’s the same type (e.g., x+y) Sometimes it’s different (e.g., x>y)