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Delphi Language Guide

Structured types

Multidimensional dynamic arrays

To declare multidimensional dynamic arrays, use iterated array of ... constructions.

For example,

type TMessageGrid = array of array of string;

var Msgs: TMessageGrid;

declares a two-dimensional array of strings. To instantiate this array, call SetLength

with two integer arguments. For example, if I and J are integer-valued variables,

SetLength(Msgs,I,J);

allocates an I-by-J array, and Msgs[0,0] denotes an element of that array.

You can create multidimensional dynamic arrays that are not rectangular. The first

step is to call SetLength, passing it parameters for the first n dimensions of the array.

For example,

var Ints: array of array of Integer;

SetLength(Ints,10);

allocates ten rows for Ints but no columns. Later, you can allocate the columns one at

a time (giving them different lengths); for example

SetLength(Ints[2], 5);

makes the third column of Ints five integers long. At this point (even if the other

columns haven’t been allocated) you can assign values to the third column—for

example, Ints[2,4] := 6.

The following example uses dynamic arrays (and the IntToStr function declared in

the SysUtils unit) to create a triangular matrix of strings.

var

A : array of array of string;

I, J : Integer;

begin

SetLength(A, 10);

for I := Low(A) to High(A) do

begin

SetLength(A[I], I);

for J := Low(A[I]) to High(A[I]) do

A[I,J] := IntToStr(I) + ',' + IntToStr(J) + ' ';

end;

Array types and assignments

Arrays are assignment-compatible only if they are of the same type. Because the

Delphi language uses name-equivalence for types, the following code will not

compile.

var

Int1: array[1..10] of Integer;

Int2: array[1..10] of Integer;

Int1 := Int2;