post-scarcity/src/c/ops/assoc.c

/**
 *  ops/assoc.c
 *
 *  Post Scarcity Software Environment: assoc.
 *
 *  Search a store for the value associated with a key.
 *
 *  (c) 2026 Simon Brooke <simon@journeyman.cc>
 *  Licensed under GPL version 2.0, or, at your option, any later version.
 */

#include <stdbool.h>

#include "memory/node.h"
#include "memory/pointer.h"
#include "memory/pso2.h"
#include "memory/tags.h"

#include "payloads/cons.h"
#include "payloads/stack.h"

#include "ops/eq.h"
#include "ops/stack_ops.h"
#include "ops/truth.h"

/**
 * @brief: fundamental search function; only knows about association lists
 *
 * @param key a pointer indicating the key to search for;
 * @param store a pointer indicating the store to search;
 * @param return_key if a binding is found for `key` in `store`, if true
 * 			return the key found in the store, else return the value
 *
 * @return nil if no binding for `key` is found in `store`; otherwise, if
 * 			`return_key` is true, return the key from the store; else
 * 			return the binding.
 */
struct pso_pointer search( struct pso_pointer key,
                           struct pso_pointer store, bool return_key ) {
    struct pso_pointer result = nil;
    bool found = false;

    if ( consp( store ) ) {
        for ( struct pso_pointer cursor = store;
              consp( cursor ) && found == false; cursor = c_cdr( cursor ) ) {
            struct pso_pointer pair = c_car( cursor );

            if ( consp( pair ) && c_equal( c_car( pair ), key ) ) {
                found = true;
                result = return_key ? c_car( pair ) : c_cdr( pair );
            }
        }
    }

    return result;
}

/**
 * @prief: bootstap layer assoc; only knows about association lists.
 *
 * @param key a pointer indicating the key to search for;
 * @param store a pointer indicating the store to search;
 *
 * @return a pointer to the value of the key in the store, or nil if not found
 */
struct pso_pointer c_assoc( struct pso_pointer key, struct pso_pointer store ) {
    return search( key, store, false );
}

/**
 * @prief: bootstap layer interned; only knows about association lists.
 *
 * @param key a pointer indicating the key to search for;
 * @param store a pointer indicating the store to search;
 *
 * @return a pointer to the copy of the key in the store, or nil if not found.
 */
struct pso_pointer c_interned( struct pso_pointer key,
                               struct pso_pointer store ) {
    return search( key, store, true );
}

/**
 * @prief: bootstap layer interned; only knows about association lists.
 *
 * @param key a pointer indicating the key to search for;
 * @param store a pointer indicating the store to search;
 *
 * @return `true` if a pointer the key was found in the store..
 */
bool c_internedp( struct pso_pointer key, struct pso_pointer store ) {
    return !c_nilp( search( key, store, true ) );
}

/**
 * @prief: bootstap layer assoc; Lisp calling signature.
 *
 * @return a pointer to the value of the key in the store, or nil if not found
 */
struct pso_pointer assoc(
#ifndef MANAGED_POINTER_ONLY
                             struct pso4 *frame,
#endif
                             struct pso_pointer frame_pointer) {
#ifdef MANAGED_POINTER_ONLY
    struct pso4 *frame = pointer_to_pso4( frame_pointer );
#endif
    struct pso_pointer key = fetch_arg( frame, 0 );
    struct pso_pointer store = or( make_frame( 2, frame_pointer,
    		fetch_arg( frame, 1 ), frame->payload.stack_frame.env));

    return c_assoc( key, store );
}

/**
 * @prief: bootstap layer interned; Lisp calling signature.
 *
 * @return a pointer to the copy of the key in the store, or nil if not found.
 */
struct pso_pointer interned(
#ifndef MANAGED_POINTER_ONLY
                                struct pso4 *frame,
#endif
                                struct pso_pointer frame_pointer) {
#ifdef MANAGED_POINTER_ONLY
    struct pso4 *frame = pointer_to_pso4( frame_pointer );
#endif
    struct pso_pointer key = fetch_arg( frame, 0 );
    struct pso_pointer store = or( make_frame( 2, frame_pointer,
    		fetch_arg( frame, 1 ), frame->payload.stack_frame.env));

    return c_interned( key, store );
}

/**
 * @prief: bootstap layer interned?; Lisp calling signature.
 *
 * @return `t` if a pointer to a copy of `key` is found in the store, or `nil` if not found.
 */
struct pso_pointer internedp(
#ifndef MANAGED_POINTER_ONLY
                                 struct pso4 *frame,
#endif
                                 struct pso_pointer frame_pointer) {
#ifdef MANAGED_POINTER_ONLY
    struct pso4 *frame = pointer_to_pso4( frame_pointer );
#endif
    struct pso_pointer key = fetch_arg( frame, 0 );
    struct pso_pointer store = or( make_frame( 2, frame_pointer,
    		fetch_arg( frame, 1 ), frame->payload.stack_frame.env));

    return c_internedp( key, store ) ? t : nil;
}