clingo_ground_event_handler Struct Reference

The ground event handler interface. More...

#include <ground.h>

Public Attributes
bool(*	callable )(char const *name, size_t name_size, size_t arguments_size, void *data, bool *result)
	Check if the function with the given name and number of arguments is callable.
bool(*	call )(clingo_lib_t *lib, clingo_location_t const *location, char const *name, size_t name_size, clingo_symbol_t const *arguments, size_t arguments_size, void *data, clingo_symbol_callback_t symbol_callback, void *symbol_callback_data)
	Callback function to implement external functions.
void(*	finish )(clingo_ground_result_t result, void *data)
	Callback to notify that the grounding has finished.
void(*	free )(void *data)
	Callback to free the userdata of the handler.

Detailed Description

The ground event handler interface.

Member Data Documentation

call

bool(* clingo_ground_event_handler::call) (clingo_lib_t *lib, clingo_location_t const *location, char const *name, size_t name_size, clingo_symbol_t const *arguments, size_t arguments_size, void *data, clingo_symbol_callback_t symbol_callback, void *symbol_callback_data)

Callback function to implement external functions.

If an external function of form @name(parameters) occurs in a logic program, then this function is called with its location, name, parameters, and a callback to inject symbols as arguments. The callback can be called multiple times; all symbols passed are injected.

If a (non-recoverable) clingo API function fails in this callback, for example, the symbol callback, the callback must return its return code. In case of errors not related to clingo, this function can use clingo_set_error().

Parameters

[in]	lib	the library object
[in]	location	location from which the external function was called
[in]	name	name of the called external function
[in]	arguments	arguments of the called external function
[in]	arguments_size	number of arguments
[in]	data	user data of the callback
[in]	symbol_callback	function to inject symbols
[in]	symbol_callback_data	user data for the symbol callback (must be passed untouched)

Returns

whether the call was successful

See also

clingo_control_ground()

The following example implements the external function @f() returning 42.

bool
call(clingo_lib_t *lib,
     clingo_location_t const *location,
     char const *name,
     size_t name_size,
     clingo_symbol_t const *arguments,
     size_t arguments_size,
     void *data,
     clingo_symbol_callback_t symbol_callback,
     void *symbol_callback_data) {
  if (size == 1 && strncmp(name, "f", 1) == 0 && arguments_size == 0) {
    clingo_symbol_t sym;
    sym = clingo_symbol_create_number(42);
    return symbol_callback(&sym, 1, symbol_callback_data);
  }
  return clingo_set_error(lib, clingo_result_runtime, "function not found", 18);
}

callable

bool(* clingo_ground_event_handler::callable) (char const *name, size_t name_size, size_t arguments_size, void *data, bool *result)

Check if the function with the given name and number of arguments is callable.

Parameters

[in]	name	name of the called external function
[in]	name_size	size of the name
[in]	arguments_size	number of arguments
[in]	data	user data of the callback
[out]	result	whether the function is callable

Returns

whether the call was successful

finish

void(* clingo_ground_event_handler::finish) (clingo_ground_result_t result, void *data)

Callback to notify that the grounding has finished.

This can be used for thread synchronization as the function is not called in the main thread when grounding asynchronously.

Parameters

result	the ground result
data	the user data

free

void(* clingo_ground_event_handler::free) (void *data)

Callback to free the userdata of the handler.

Parameters

data	the user data

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The documentation for this struct was generated from the following file:

• clingo/ground.h