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:   := Delphi uses := for it's assignment operator. Syntax Example: var FullName: String; Age: Integer; begin FullName := "Randy Spitz"; Age := 38; end	Corel Paradox:   = ObjectPAL uses = for it's assignment operator. Syntax Example:   var  FullName String    Age SmallInt endVar FullName = "Randy Spitz" Age = 42

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:   =, <> Common comparison operators: = equal <> not equal < less than > greater than <= less than or equal >= greater than or equal Syntax Example: //Does Delphi evaluate the math correctly? Yes! //Refer to math.pas MaxSingle for more info. if (0.1 + 0.1 + 0.1 = 0.3) then ShowMessage('correct') else ShowMessage('not correct')  Delphi Comparison Operators (=, <>)	Corel Paradox:   =, <> Common comparison operators: = equal <> not equal < less than > greater than <= less than or equal >= greater than or equal Syntax Example: 'Does ObjectPAL evaluate the math correctly? No! If .1 + .1 + .1 = .3 Then msgInfo("", "correct") Else msgInfo("", "not correct") endIf  ObjectPAL Comparison Operators (=, <>)

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:   length(s) = 0 Length() or SizeOf() will correctly identify an unassigned string variable or an empty string. Syntax Example: if length(s) = 0 then   ShowMessage('empty string');

Corel Paradox:   isBlank() or not isAssigned() In ObjectPAL, an empty variable can be unassigned (essentially null) or blank (equivalent to ""). You have to use both isBlank and isAssigned to check for an empty string. Syntax Example: var  s String endVar ;s = ""  ;Uncomment to test 2nd case. if isBlank(s) or not isAssigned(s) Then  msgInfo("", "empty string") endIf  ObjectPAL Empty String Check (isBlank() or not isAssigned())

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:  Delphi 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 The Delphi compiler default is to short circuit multi argument boolean expressions when the result is known before the evaluation completes. To disable short circuiting, use the {$B+} compiler directive. To reset it back to the compiler default of short circuting, use the {$B-} compiler directive. Syntax Example: //Given expressions a, b, c, and d: if Not (a and b) and (c or d) then   //Do something.  Delphi Logical Operators

Corel Paradox:  ObjectPAL logical operators: and and, as in this and that or or, as in this or that Not Not, as in Not This Like VBA, ObjectPAL 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. endIf  ObjectPAL Logical Operators

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:  An operation with only one operand (a single input). In Object Pascal, a unary operator has the highest precedence and always precedes its operand (for example, -B), except for the  ^ pointer operator, which follows its operand (for example, P^). In addition to the obvious +, -, and Not operators, Delphi also offers: ^ Pointer @ returns the address of a variable, function, procedure, or method; a pointer to its operand. inc() Increment dec() Decrement The TYPE operator is also a unary operator and is valuated at compile time. The TYPE operator returns the size in bytes of the operand, More Info / Comment

Corel Paradox:  The ObjectPAL unary operators are: + - Not More Info / Comment