Task: Ternary logic




Go: package main

import "fmt"

type trit int8

const (
    trFalse trit = iota - 1
    trMaybe
    trTrue
)

func (t trit) String() string {
    switch t {
    case trFalse:
        return "False"
    case trMaybe:
        return "Maybe"
    case trTrue:
        return "True "
    }
    panic("Invalid trit")
}

func trNot(t trit) trit {
    return -t
}

func trAnd(s, t trit) trit {
    if s < t {
        return s
    }
    return t
}

func trOr(s, t trit) trit {
    if s > t {
        return s
    }
    return t
}

func trEq(s, t trit) trit {
    return s * t
}

func main() {
    trSet := []trit{trFalse, trMaybe, trTrue}

    fmt.Println("t     not t")
    for _, t := range trSet {
        fmt.Println(t, trNot(t))
    }

    fmt.Println("\ns     t     s and t")
    for _, s := range trSet {
        for _, t := range trSet {
            fmt.Println(s, t, trAnd(s, t))
        }
    }

    fmt.Println("\ns     t     s or t")
    for _, s := range trSet {
        for _, t := range trSet {
            fmt.Println(s, t, trOr(s, t))
        }
    }

    fmt.Println("\ns     t     s eq t")
    for _, s := range trSet {
        for _, t := range trSet {
            fmt.Println(s, t, trEq(s, t))
        }
    }
}



PHP: #!/usr/bin/php
<?php

# defined as numbers, so I can use max() and min() on it
if (! define('triFalse',0))  trigger_error('Unknown error defining!', E_USER_ERROR);
if (! define('triMaybe',1))  trigger_error('Unknown error defining!', E_USER_ERROR);
if (! define('triTrue', 2))  trigger_error('Unknown error defining!', E_USER_ERROR);

$triNotarray = array(triFalse=>triTrue, triMaybe=>triMaybe, triTrue=>triFalse);

# output helper
function triString ($tri) {
    if ($tri===triFalse) return 'false  ';
    if ($tri===triMaybe) return 'unknown';
    if ($tri===triTrue)  return 'true   ';
    trigger_error('triString: parameter not a tri value', E_USER_ERROR);
}

function triAnd() {
    if (func_num_args() < 2) 
       trigger_error('triAnd needs 2 or more parameters', E_USER_ERROR);
    return min(func_get_args());
}

function triOr() {
    if (func_num_args() < 2) 
       trigger_error('triOr needs 2 or more parameters', E_USER_ERROR);
    return max(func_get_args());
}

function triNot($t) {
    global $triNotarray; # using result table
    if (in_array($t, $triNotarray)) return $triNotarray[$t];
    trigger_error('triNot: Parameter is not a tri value', E_USER_ERROR);
}

function triImplies($a, $b) {
    if ($a===triFalse || $b===triTrue)  return triTrue;
    if ($a===triMaybe || $b===triMaybe) return triMaybe;
    # without parameter type check I just would return triFalse here
    if ($a===triTrue &&  $b===triFalse) return triFalse;
    trigger_error('triImplies: parameter type error', E_USER_ERROR);
}

function triEquiv($a, $b) {
    if ($a===triTrue)  return $b;
    if ($a===triMaybe) return $a;
    if ($a===triFalse) return triNot($b);
    trigger_error('triEquiv: parameter type error', E_USER_ERROR);
}

# data sampling

printf("--- Sample output for a equivalent b ---\n\n");

foreach ([triTrue,triMaybe,triFalse] as $a) {
    foreach ([triTrue,triMaybe,triFalse] as $b) {
        printf("for a=%s and b=%s a equivalent b is %s\n",
               triString($a), triString($b), triString(triEquiv($a, $b)));
    }
}