# call

A task specification for a pool of another language's workers.

Usage

[Source](https://github.com/shikokuchuo/pymizu/blob/main/python/pymizu/__init__.py#L425-L507)

``` python
call(
    name=None,
    /,
    *args,
    source=None,
    **kwargs,
)
```

Describes a call for [`Pool.submit()`](../reference/Pool.submit.md#pymizu.Pool.submit): a qualified name (`"mod.fn"` for Python workers, `"pkg::fn"` for R workers) or a `source=` string in the workers' language, plus the constant arguments. The spec describes a call; it is not a value. The language never appears at the call site -- [Pool.submit](../reference/Pool.submit.md#pymizu.Pool.submit) resolves the workers' language from the pool itself -- and a bare (unqualified) name errors at submit, not here.

## Parameters

`name: str | None = None`  
A qualified name: `"mod.fn"` for Python workers, `"pkg::fn"` for R workers.

`args: _Any = ()`  
Constant positional arguments of the call.

`source: str | None = None`  
A source string in the workers' language. Exactly one of `name` or `source` must be given.

`kwargs: _Any = {}`  
Constant keyword arguments of the call.

## Details

Unnamed arguments map to the positional list and keyword arguments to the named dict, matching R's mixed-call convention. Arguments must be portable values (the interchange subset documented under [`Channel.send()`](../reference/Channel.send.md#pymizu.Channel.send)): a non-portable argument raises [`DeclinedError`](../reference/DeclinedError.md#pymizu.DeclinedError) at submit, never a fallback.

A `source=` task evaluates in a fresh namespace with the keyword arguments bound as names and positional arguments bound as `_1`, `_2`, … The result is the trailing expression's value, or None when the source ends with a statement.

Large arguments cross to foreign workers by reference rather than by copy: one fresh buffer argument past the zero-copy floor stages a single layout write into a shared region (the worker reads a view over it), and an argument that is already a shared view crosses as its identifier alone -- zero payload bytes. On a pool whose workers predate the ref reader, such a task declines locally at submit naming the remedy.

## Examples

A spec task also runs on a normal (Python-worker) pool:

``` python
>>> import pymizu
>>> with pymizu.Pool.create(2) as pool:
...     task = pool.submit(pymizu.call("math.sqrt", 2.0))
...     results = pool.collect_all([task], timeout=10)
>>> results
[1.4142135623730951]
```