Creating an Array: Difference between revisions

=={{header|ALGOL 68}}==

As with all [[ALGOL 68]] declarations the programmer has the choice of

using the full declaration syntax, or using [[syntactic sugar]] - c.f. "sugared" variables below.

Example of array of 10 integer types:

REF []INT numbers = HEAP [1:10] INT;

HEAP [1:10]INT sugared hnumbers; # from global memory #

LOC [1:10]INT sugared lnumbers1; # from the stack #

[10]INT sugared lnumbers2; # from the stack - LOC scope is implied #

Note that the array can be taken from the heap, or stack.

Example of array of 3 string types:

[]STRING cwords = ( "these", "are", "arrays" ); # array is a constant and read-only (=) #

[3]STRING vwords := ( "these", "are", "arrays" ); # array is a variable and modifiable (:=) #

You can also declare the size of the array and initialize the values at the same time:

REF []INT more numbers = LOC [3]INT := ( 21, 14 ,63 );

[]INT sugared more numbers = ( 21, 14 ,63 );

For Multi-Dimensional arrays you declare them the same except for a comma in the type declaration.

The following creates a 3x2 int matrix

REF [][]INT number matrix = LOC [3][2] INT;

[3,2]INT sugared number matrix1; # an matrix of integers #

[3][2]INT sugared number matrix2; # an array of arrays #

As with the previous examples you can also initialize the values of the array, the only

difference being each row in the matrix must be enclosed in its own braces.

[][]STRING string matrix = ( ("I","swam"), ("in","the"), ("freezing","water") );

or

REF [][] STRING funny matrix = LOC [2][2]STRING := ( ("clowns", "are") , ("not", "funny") );

[2][2] STRING sugared funny matrix := ( ("clowns", "are") , ("not", "funny") );

Further, the arrays can start at any number:

[-10:10] INT balanced; # for example -10 #

If the array is expected to change size in future, then the programmer can also declare it FLEX.

FLEX [-10:10] INT flex balanced;

This next piece of code creates an array of integers. The value of

each integer "pointed at" is the square of its index in the array.

[-10:10] REF INT array of pointers to ints;

FOR index FROM LWB array of pointers to ints TO UPB array of pointers to ints DO

array of pointers to ints[index] := HEAP INT := i*i # allocate global memory #

OD

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