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.

Delphi Prism:   := Same as Delphi. Syntax Example: FullName: String; Age: Integer; FullName := "Randy Spitz"; Age := 38;	PHP:   = PHP uses = for it's assignment operator. Syntax Example: $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.

Delphi Prism:   =, <> Same as Delphi. Common comparison operators: = equal <> not equal < less than > greater than <= less than or equal >= greater than or equal Syntax Example: //Does Prism evaluate the math correctly? No! //This is different than later versions of //Delphi that muse MaxSingle in math.pas. If .1 + .1 + .1 = .3 Then MessageBox.Show("correct") Else MessageBox.Show("not correct");

PHP:   ==, != or <> Common comparison operators: == equal != or <> not equal < less than > greater than <= less than or equal >= greater than or equal PHP 4 and above also offers === for indentical (equal plus same type) and !== for not identical (not equal or not same type). Syntax Example: //Does PHP evaluate the math correctly? No! if (.1 + .1 + .1 == .3) { echo "correct"; } else { echo "not correct"; }

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.

Delphi Prism:   length In Prism, a string can be nil (unassigned), assigned an empty string (""), or assigned a value.  Therefore, to check if a string is empty, you have to check against both nil and (""). Alternatively, you can check the length of the string or use String.IsNullOrEmpty. Syntax Example: var s: String; if (s = nil) or (s = '') then   MessageBox.Show("empty string"); or use length: if length(s) = 0 then   MessageBox.Show("empty string");  Delphi Prism Empty String Check (length)

[Not specified yet. Coming...]

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.

Delphi Prism:  Prism logical operators: and and, as in this and that or or, as in this or that not Not, as in Not This xor either or, as in this or that but not both Syntax Example:   //Given expressions a, b, c, and d: if Not (a and b) and (c or d) then   //Do something.	PHP:   and, &&, or, ||, !, Xor PHP logical operators: and, && and, as in this and that or, || or, as in this or that ! Not, as in Not This Xor 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. };

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.

Delphi Prism:  The obvious Prism unary operators are +, -, and Not. + Plus - Minus Not Bitwise Not Inc() Increment Dec() Decrement Syntax Example: var i: Integer := 1; Inc(i); MessageBox.Show("" + i);  //Displays 2  Delphi Prism Unary Operators	PHP:  A unary operator operates on only one value. PHP Examples: ! negation operator ++ increment operator -- decrement operator  PHP Unary Operators