Cross Ref > Data Structures

Languages Focus

A data structure in which individual values (called elements or items) may be located by reference to one or more integer index variables, the number of such indices being the number of dimensions in the array.

Arrays can start with an index value of 0 or 1, sometimes referred to as 0 based or 1 based.

Corel Paradox:   Array[] type Arrays in ObjectPAL use a 1-based subscript (also known as an index). Use [] with a subscript to refer to an element (i.e. MyArray[1], MyArray[2]). The number of elements for a given array in ObjectPAL are either fixed or resizeable. Specify the size when you declare it for fixed. Use size() to get the number of elements, size() returns 0 if the array has no elements. Use setSize(), grow(), addLast(), etc. to add elements to an array. Syntax Example: var   MyArray Array[4] String ;Fixed size array.   i LongInt endVar MyArray[1] = "Mike" MyArray[2] = "Lisa" MyArray[3] = "Felicia" MyArray[4] = "Nathan" if MyArray.size() > 0 then   for i from 1 to MyArray.size()     msgInfo("", MyArray[i])   endFor endIf  ObjectPAL Array (Array[] type)

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Languages Focus

Associative arrays are also known as a dictionary or a hash table in other languages.

Corel Paradox:   DynArray In ObjectPAL associative arrays are known as dynamic arrays. Syntax Example: var myDynArray   DynArray[] String endVar   myDynArray["Last_Name"] = "Spitz" myDynArray["First_Name"] = "Randy" myDynArray.view()  ObjectPAL Associative Array (DynArray)

Java:   HashMap() An associative array links a set of keys to a set of values. In Java, associative arrays are implemented as Maps. This will print "Arizona." Syntax Example: import java.util.*; public class Maps {     public static void main(String[] args)     {         Map states = new HashMap();                 states.put("CA", "California");         states.put("FL", "Florida");         states.put("AZ", "Arizona");         System.out.println(states.get("AZ"));     } }  Associative Arrays in Java (a Map)

General Info: Pointers / References

A pointer is a variable type that allows you to refer indirectly to another object. Instead of holding data, a pointer holds the address to data -- the address of another variable or object. You can change the address value a pointer points to thus changing the variable or object the pointer is pointing to.

A reference is a type of pointer that cannot change and it must always point to a valid storage (no nulls).

Corel Paradox:  ObjectPAL doesn't have a developer defined pointer type except for use with DLLs where you use a special CPTR uses keyword to refer to a DLL string pointer data type. Syntax Example:   Uses Tapi32 tapiRequestMakeCall(sNumber CPTR, sAppName CPTR, sLogName CPTR, sComment CPTR) CLONG endUses	Java:   Not Supported Java does not offer developer defined pointers.