# `Mojoler.POC`
[🔗](https://github.com/thanos/mojoler/blob/v0.1.0/lib/mojoler/poc.ex#L1)

Checked signed 64-bit addition, loaded from `priv/native/libpoc.so`.

The entry name is `Elixir.Mojoler.POC`. `nif_init` writes that string
into `ErlNifEntry.name`.

# `i64`

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

A signed 64-bit integer. Values outside this range are not terms this NIF accepts.

# `add`

```elixir
@spec add(i64(), i64()) :: i64()
```

Returns `a + b` when both arguments and the sum fit in a signed 64-bit integer.

`a` and `b` are integers. Floats, atoms, and binaries are rejected.
There is no optional argument.

## Returns

The sum, an integer.

## Raises

  * `ArgumentError` when `a` or `b` is not an integer, does not fit in
    signed 64 bits, or the sum would overflow

A wrong arity never reaches this function. Elixir raises `UndefinedFunctionError`.

## Examples

    iex> Mojoler.POC.add(20, 22)
    42

    iex> Mojoler.POC.add(-5, -7)
    -12

    iex> Mojoler.POC.add(1, :nope)
    ** (ArgumentError) argument error

    iex> Mojoler.POC.add(9_223_372_036_854_775_807, 1)
    ** (ArgumentError) argument error

# `load_nif`

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

Loads `priv/native/libpoc.so`.

Called from this module by `@on_load`. A second call in the same VM returns
an error. The library stays loaded until the OS process exits.

## Returns

  * `:ok` on the first load
  * `{:error, {:reload, charlist}}` when OTP rejects a second load
  * `{:error, reason}` when the file is missing or the entry is refused

## Examples

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

# `reload`

```elixir
@spec reload() :: :ok | {:error, term()}
```

Loads the library again.

Same contract as `load_nif/0`. The suite uses it to observe OTP's reload refusal.

## Examples

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

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*Consult [api-reference.md](api-reference.md) for complete listing*