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arrays [2019/04/07 22:24] – created neilsarrays [2019/06/27 07:42] – neils
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 ====== Arrays ====== ====== 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) and only integers may be used as indices.+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): The syntax to define array is the following (note the square brackets):
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   end   end
  
-Arrays are not initialized, 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'' 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]   dim a[10]
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   rem ** this will print an undefined number **   rem ** this will print an undefined number **
  
-Important: 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.+**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~~