128 lines
3.6 KiB
C
128 lines
3.6 KiB
C
/**
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* ops/truth.c
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*
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* Post Scarcity Software Environment: nil? true? not.
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*
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* Functions associated with truthiness.
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*
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* (c) 2026 Simon Brooke <simon@journeyman.cc>
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* Licensed under GPL version 2.0, or, at your option, any later version.
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*/
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#include <stdbool.h>
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#include "memory/node.h"
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#include "memory/pointer.h"
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#include "memory/pso4.h"
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#include "ops/stack_ops.h"
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/**
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* @brief true if `p` points to `nil`, else false.
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*
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* Note that every node has its own copy of `t` and `nil`, and each instance of
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* each is considered equivalent. So we don't check the node when considering
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* whether `nil` really is `nil`, or `t` really is `t`.
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*
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* @param p a pointer
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* @return true if `p` points to `nil`.
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* @return false otherwise.
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*/
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bool c_nilp( struct pso_pointer p ) {
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return ( p.page == 0 && p.offset == 0 );
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}
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/**
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* @brief `true` if `p` points to `t`, else `false`.
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*
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* Note that every node has its own copy of `t` and `nil`, and each instance of
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* each is considered equivalent. So we don't check the node when considering
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* whether `nil` really is `nil`, or `t` really is `t`.
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*
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* Note that the offset is 4 because `t` should be the second pso2 allocated,
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* the offset is given in words, and the size of a pso2 should be four words
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*
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* @param p a pointer
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* @return true if `p` points to `t`.
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* @return false otherwise.
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*/
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bool c_truep( struct pso_pointer p ) {
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return ( p.page == 0 && p.offset == 4 );
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}
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/**
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* @brief return `t` if the first argument in this frame is `nil`, else `t`.
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*
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* @param frame_pointer A pointer to the current stack frame;
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* @return `t` if the first argument in this frame is `nil`, else `t`
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*/
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struct pso_pointer nilp( struct pso_pointer frame_pointer ) {
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struct pso4 *frame = pointer_to_pso4( frame_pointer );
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return ( c_nilp( fetch_arg( frame, 0 ) ) ? t : nil );
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}
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/**
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* @brief return `t` if the first argument in this frame is `t`, else `nil`.
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*
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* @param frame_pointer A pointer to the current stack frame;
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* @return `t` if the first argument in this frame is `t`, else `nil`.
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*/
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struct pso_pointer truep( struct pso_pointer frame_pointer ) {
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struct pso4 *frame = pointer_to_pso4( frame_pointer );
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return ( c_truep( fetch_arg( frame, 0 ) ) ? t : nil );
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}
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/**
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* @brief return `t` if the first argument in this frame is not `nil`, else
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* `t`.
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*
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* @param frame_pointer A pointer to the current stack frame;
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* @return `t` if the first argument in this frame is not `nil`, else `t`.
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*/
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struct pso_pointer not( struct pso_pointer frame_pointer ) {
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struct pso4 *frame = pointer_to_pso4( frame_pointer );
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return ( !c_nilp( fetch_arg( frame, 0 ) ) ? t : nil );
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}
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/**
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* @brief (and args...)
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*
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* @return `nil` if any `arg` is `nil`, else `t`.
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*/
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struct pso_pointer and( struct pso_pointer frame_pointer ) {
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struct pso4 *frame = pointer_to_pso4( frame_pointer );
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struct pso_pointer result = t;
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for ( int arg = 0;
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c_truep( result ) && arg < frame->payload.stack_frame.args; arg++ ) {
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if ( c_nilp( fetch_arg( frame, arg ) ) ) {
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result = nil;
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break;
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}
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}
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return result;
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}
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/**
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* @brief (or args...)
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*
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* @return `t` if any `arg` is non-nil, else `nil`.
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*/
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struct pso_pointer or( struct pso_pointer frame_pointer ) {
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struct pso4 *frame = pointer_to_pso4( frame_pointer );
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struct pso_pointer result = nil;
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for ( int arg = 0;
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c_truep( result ) && arg < frame->payload.stack_frame.args; arg++ ) {
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if ( !c_nilp( fetch_arg( frame, arg ) ) ) {
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result = t;
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break;
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}
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}
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return result;
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}
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