Cross Ref > Operators

Languages Focus

Common assignment operators for languages include =, ==, and :=. An assignment operator allows you to assign a value to a variable. The value can be a literal value like "Mike" or 42 or the value stored in another variable or returned by a function.

C++/CLI:   = C++/CLI uses = for it's assignment operator. Syntax Example: int Age; string FullName; Age = 42; FullName = "Randy Spitz";	Access VBA:   = Access uses = for it's assignment operator. Syntax Example: Dim Age As Integer Dim FullName As String     FullName = "Randy Spitz" Age = 38

General Info: Round Floating Point Numbers

When comparing floating point numbers, make sure you round to an acceptable level of rounding for the type of application you are using.

Languages Focus

A comparison operator compares two values either literals as in "Hello" and 3 or variables as in X and Counter. Most languages use the same operators for comparing both numbers and strings. Perl, for example, uses separate sets of comparison operators for numbers and strings.

C++/CLI:   ==, != Same as standard C++. Common comparison operators: == equal != not equal < less than > greater than <= less than or equal >= greater than or equal Syntax Example: //Does C++/CLI evaluate the math correctly? No! if (0.1 + 0.1 + 0.1 == 0.3) MessageBox::Show("correct"); else MessageBox::Show("not correct");	Access VBA:   =, <> Save as VB Classic. Common comparison operators: = equal <> not equal < less than > greater than <= less than or equal >= greater than or equal Syntax Example: //Does Access evaluate the math correctly? No! If 0.1 + 0.1 + 0.1 = 0.3 Then MsgBox "correct" Else MsgBox "not correct" End If

Languages Focus

An empty string is a zero length string, a string that is equal to null (""), or not assigned. In some languages, you can check if a string is empty by comparing it to an empty string (""). Some languages distinguish between nil and null ("") so checking if the length is 0 is easier.

C++/CLI:   String.IsNullOrEmpty The .Net framework offers a static method in the string class: String.IsNullOrEmpty. Syntax Example: String^ s; //s = ""; //Uncomment to test 2nd case. if (String::IsNullOrEmpty(s)) {   MessageBox::Show("empty string"); }

Access VBA:   Len(s&vbNullString) In Access VBA, you have to add an empty string to the value being compared in order to get consistent results. For example, add &"" to your string varilable or it's code equivalent &vbNullString. Then compare to an empty string or verify it's length to 0 with Len. Syntax Example: All these will work for variables unassigned, set to "", or set to Null: If s&"" = "" Then   MsgBox ("Quotes with &'' say null is empty") End If If Len(s&"") = 0 Then   MsgBox ("Len with &'' says null is empty") End If If Len(s&vbNullString) = 0 Then   MsgBox ("Using vbNullString also works!") End If

Languages Focus

Logical operators perform conditional and, or, and not operations. Some languages support both binary logical operators that link two and unary logical operators negate (make opposite) the truth value of its argument. Finally, some languages short circuit logic. For example, with this or that, if this is an expression returning true, then that is never executed.

C++/CLI:  Same as C++ and Java. C# logical operators: & and, as in this and that No Short Circuit && and, as in this and that short circuits | or, as in this or that No Short Circuit || or, as in this or that short circuits ! Not, as in Not This ^ either or, as in this or that but not both Syntax Example: //Given expressions a, b, c, and d: if !((a && b) && (c || d)) {   //Do something. }

Access VBA:   and, or, not Same as VB. Access VBA logical operators: and and, as in this and that or or, as in this or that Not Not, as in Not This Access VBA never short circuits. Given the expression this or that as well as this and that, if this evaluates to false, then that is still executed. Syntax Example: 'Given expressions a, b, c, and d: If Not (a and b) and (c or d) Then   'Do something. End If  Access VBA Logical Operators (and, or, not)

General Info: Unary Operator

An operation with only one operand (a single input). Common unary operators include + plus, - minus, and bitwise not. Some operators can function as both unary and binary operators. For example, + and - operators can serve as either.

Languages Focus

What unary operators are supported in additoin to the standard plus, minus, and bitwise not.

[Not specified yet. Coming...]

Access VBA:  An operation with only one operand (a single input) such as +, -, and Not.  Access VBA Unary Operators