Arrays

Arrays must be defined using the DIM statement. As of the current version, maximum two-dimensional arrays are supported and both dimensions are limited to a length of 32767 elements. However, this is just a theoretical limit, in practice you'll run out of memory earlier. Arrays are zero-based (the first index is 0). Floats are not allowed as indices.

The syntax to define array is the following (note the square brackets):

dim variable[x_len, y_len]

Example:

dim myArr[100, 100]
let myArr[15, 2] = 3420
print myArr[15, 2]

Or:

rem ** fill an array with consecutive numbers **
dim myArr[10]
for i=0 to 9
  let myArr[i] = i
next i
print "fetch number 5 from myArr: ", myArr[5]
end

DIM does not initialize the array, which means that if you read the value of an array member without previously assigning a value to it, you will get unexpected results. For example:

dim a[10]
print a[0]
rem ** this will print an undefined number **

Important note: there is no runtime array bounds checking! The programmer has to make sure that the array subscript returns a number that is within the bounds of the array. Otherwise the result will be undefined.

Fast array lookup

If the variable and index are both byte types, the compiler can take advantage of the processor's indexed addressing mode resulting to much faster array load and store operations.

For example:

dim arr![255]
fastindex! = 42
slowindex = 42
rem -- fast lookup
item! = arr![fastindex!]
rem -- slow lookup
item! = arr![slowindex]

Discussion

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