any_function.md

any_function

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Header

#include <ext/any_function>

Overview

Provides a std::function-compatible wrapper that can be called with a std::vector<std::any>. It is useful for command queues, reflection-like dispatch, and APIs that need to store callable objects while binding arguments later.

Key APIs

• ext::any_function<R(Args...)> stores a callable and exposes both typed calls and std::any-based calls.
• push_back, set_args, and clear manage the stored argument vector used by the nullary operator()().
• call(args...) invokes the stored callable with typed arguments and returns R directly.
• invalid_argument_type and argument_count_mismatch describe failed dynamic argument conversion.

Behavior Notes

• Dynamic calls validate the number of arguments before invocation.
• Each std::any argument is cast to the function signature type; mismatches throw with the failing argument index.
• Reference wrappers are supported for pass-by-reference command patterns.

Requirements

• GCC 8.3.0+
• Clang 10.0+
• Visual Studio 2017+
• std::any required
• if constexpr required

Examples

#include <ext/any_function>

ext::any_function fn(strlen);

if (fn.call("test") == 4) {
}

if (std::any_cast<decltype(fn)::result_type>(fn({"test"})) == 4) {
}

size_t len;
std::any result;
result = fn({"test"});
if (result.has_value())
    len = std::any_cast<size_t>(result);

std::vector<std::any> args;
args.push_back("test");
result = fn(args);
if (result.has_value())
    len = std::any_cast<size_t>(result);