Mojoler.Twice (mojoler v0.1.0)

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Checked doubling of a signed 64-bit integer, loaded from priv/native/libtwice.so.

The native file imports the generated ABI. It does not declare ErlNifFunc or ErlNifEntry.

Summary

Types

i64()

A signed 64-bit integer.

Functions

double(n)

Returns 2 * n when n and the product fit in a signed 64-bit integer.

load_nif()

Loads priv/native/libtwice.so.

Types

i64()

@type i64() :: -9_223_372_036_854_775_808..9_223_372_036_854_775_807

A signed 64-bit integer.

Functions

double(n)

@spec double(i64()) :: i64()

Returns 2 * n when n and the product fit in a signed 64-bit integer.

n is an integer. There is no optional argument.

Returns

The product, an integer.

Raises

  • ArgumentError when n is not an integer, does not fit in signed 64 bits, or 2 * n would overflow

Examples

iex> Mojoler.Twice.double(21)
42

iex> Mojoler.Twice.double(0)
0

iex> Mojoler.Twice.double(-3)
-6

iex> Mojoler.Twice.double(:nope)
** (ArgumentError) argument error

iex> Mojoler.Twice.double(9_223_372_036_854_775_807)
** (ArgumentError) argument error

load_nif()

@spec load_nif() :: :ok | {:error, term()}

Loads priv/native/libtwice.so.

A second call in the same VM returns {:error, {:reload, charlist}}.

Examples

iex> Mojoler.Twice.load_nif()
{:error, {:reload, ~c"NIF library already loaded (reload disallowed since OTP 20)."}}