Retrieving an Element of an Array: Difference between revisions

 

A Static array definition:

The base index can be freely chosen:

Indeed, the "1 .. 10" resp. "7 .. 16" are actually ''types'': they are integer subrange types. Arrays can also be indexed by enumeration types or enumeration subrange types:

rainbowcolor = (red, orange, yellow, green, blue, violet);

var

i := foo[red]; { allowed indices are red, orange, yellow, green, blue, violet }

i := bar[green]; { allowed indices are yellow, green, blue }

A Dynamic Array type in Delphi:

An "old school" dynamic array in the various flavors of pascal

A dynamic array in Extended Pascal:

intarray(n: integer) = array[1 .. n] of integer; { base index 1 }

var

i := foo[2];

dispose(foo); { get rid of the array }

In the case of the static array, the compiler generates the code to allocate the required memory to hold 10 integers.

 

In the Delphi style ---dynamic--- array you must set its length:

In the "old school" style of dynamic arrays, you created a point to the zero length declaration and then allocated memory to it with GetMem

 

All arrays are accessed the same way regardless of declaration method.

 

where n is the array index who's base is either 1 or 0 depending on how it was declared.