NAME

cru_nop - nullary operator function type used in the cru library

SYNOPSIS

#include <cru/cru.h>

typedef void* (*cru_nop)(int *)

DESCRIPTION

A user-defined nullary operator takes only a pointer to an initially zero error code as an argument and returns a constant value.

RETURN VALUE

The operator may return either a scalar value or a pointer to the heap.

• In the case of a scalar value, the result is required to be identical on every invocation.
• In the case of a pointer, the result ordinarily should be a pointer to a newly allocated copy of an identical result on every invocation.
• Alternatively, applications may opt to return a pointer to a shared copy of the result. In that case both the operator and the corresponding cru_destructor function are responsible for implementing thread-safe reference counting.

ERRORS

If a nullary operator sets the error code to any non-zero value, the cru API function invoking it terminates early without completing, and propagates the same error code to its caller.

Applications can report POSIX error codes or define special purpose codes, but should not redefine any that clash with those reserved by cru as declared in the error_codes.h header file.

NOTES

Applications pass nullary operators to cru through the vacuous_case field in a cru_fold structure as an optional way of defining the effect of folding over an empty set. The result is application-specific. For example, the sum of an empty set of numbers would be zero, whereas the product of an empty set of numbers is conventionally taken to be unity.

FILES

/usr/local/include/cru/function_types.h

/usr/local/include/cru/data_types.h

/usr/local/include/cru/error_codes.h

SEE ALSO

cru, cru_bop, cru_bpred, cru_builder, cru_built, cru_cbop, cru_classifier, cru_class_of, cru_class_size, cru_composed, cru_composer, cru_connect, cru_connector, cru_cqop, cru_crossed, cru_crosser, cru_ctop, cru_ctop_pair, cru_ctop_quad, cru_data_types, cru_deduplicated, cru_destructor, cru_destructor_pair, cru_edge_count, cru_fabricated, cru_fabricator, cru_filter, cru_filtered, cru_fold, cru_free_kill_switch, cru_free_later, cru_free_now, cru_free_partition, cru_function_types, cru_get, cru_hash, cru_induced, cru_inducer, cru_kernel, cru_kill, cru_killed, cru_mapreduced, cru_mapreducer, cru_merged, cru_merger, cru_mutated, cru_mutator, cru_new_kill_switch, cru_order, cru_order_pair, cru_partition_of, cru_plan, cru_postponed, cru_postponer, cru_prop, cru_prop_pair, cru_pruner, cru_qop, cru_qpred, cru_set, cru_sig, cru_singleton, cru_split, cru_splitter, cru_spread, cru_strerror, cru_stretch, cru_stretched, cru_stretcher, cru_subconnector, cru_terminus_count, cru_top, cru_tpred, cru_united, cru_uop, cru_vertex_count, cru_zone

AUTHOR

Dennis Furey (milonga@delayinsensitive.com)

PROJECT PAGE

https://github.com/gueststar/cru