Const and Dim

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The dim statement is used to declare and optionally define a variable of a specific type. Dim statements are allowed in the prologue section of a module, a subroutine or a function (this is always before a do..end statement).

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' module level declaration
dim x: int;

main do
  x = 12;
  print(x);
end

Variables can be initialized (defined) upon declaration:

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' declaration and initial definition
dim x: int = 12;

main do
  print(x);
end

Initial definitions are limited to numeric and alphanumeric (string) literals (aka immediates), or constants (fixed references to immediates). It is not possible to assign a function or expression upon declaration. If a variable is assigned a constant, the variable type must match the constant type. With option strict enabled, types must match exactly:

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option strict;

const C = 12;         ' implicit int8 (smallest type)
dim x: int = C;       ' error, must be of type int8

However, it is allowed to explicitly set a constant’s type:

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option strict;

const C: int = 12;    ' explicit int
dim x: int = C;       ' OK

As with module-level declarations (see also global and extern), local constants and variables can also be declared using a is..end block:

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sub test()
  dim is
    p: ptr;
    n: int = 240;
    m: uint8;
  end
do
  p = aof(n);
  m = bya(p);
  print(m);
end

Constants can be passed as argument to a subroutine or function, but they cannot be passed by reference. The following example generates a compile-error:

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decl sub test(ref a: uint8);

const C = 15;

main
do
  test(C);   ' error: passing constant by reference
end

sub test(ref a: uint8)
do
  a = a + 240;
end