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Mayoría de tres (votación 2 de 3): tabla de verdad, mapa de Karnaugh y forma NAND

Votación 2 de 3, (A AND B) OR (A AND C) OR (B AND C): la tabla de ocho filas, un mapa de Karnaugh con tres grupos solapados, las formas normales y la construcción NAND de 9 compuertas.

Tres votantes, A, B y C, dicen sí o no, y la salida es sí cuando al menos dos coinciden. La fórmula enumera los tres pares posibles y los une con OR; el motor la lee como que majority es verdadero exactamente cuando al menos uno de los pares A AND B, A AND C o B AND C es verdadero por completo. En la tabla de ocho filas eso ocurre en cuatro, Σm(3, 5, 6, 7): las tres filas con exactamente dos síes y la fila con tres.

La función no es tautología, contraejemplo A = FALSO, B = FALSO, C = FALSO, y es satisfacible, testigo A = FALSO, B = VERDADERO, C = VERDADERO. El simplificador no encontró ninguna ley que acorte los cinco operadores, y la FND es la original. La FNC, con dos distributividades, dos absorciones y una idempotencia, es (A OR B) AND (A OR C) AND (B OR C). El mapa de Karnaugh dibuja tres grupos de dos celdas, A AND B, A AND C y B AND C, todos con la celda 7 en común, tres implicantes primos, y deriva la original. Compuertas: 9 NAND, 39 NOR.

La mayoría es el votador del hardware con redundancia modular triple, la regla de quórum de los comités pequeños y una función de acarreo habitual: la página del acarreo del sumador completo muestra la misma tabla de verdad a partir de otra fórmula. En código suele aparecer disfrazada de recuento, votes >= 2, que funciona hasta que alguien añade un cuarto votante y el umbral deja de significar mayoría. El motor escribe el recuento como una sola compuerta, AT_LEAST(2; A, B, C), y la ley de desarrollo de una restricción de recuento es la reescritura que la convierte en los tres pares. Los tres grupos solapados del mapa explican por qué no se puede quitar ningún término: todos los pares cubren la celda 7, la de todo verdadero, pero cada uno posee además una celda a la que ningún otro par llega.

majority := (A AND B) OR (A AND C) OR (B AND C) · salida

Comprobaciones exactas

¿Siempre verdadera (tautología)? No Contraejemplo: A = F, B = F, C = F · Exhaustively checked and solver cross-checked · 1 filas
¿Siempre falsa (contradicción)? No Contraejemplo: A = F, B = V, C = V · Exhaustively checked and solver cross-checked · 4 filas
¿Puede ser verdadera? Sí Asignación de ejemplo: A = F, B = V, C = V · Exhaustively checked and solver cross-checked · 4 filas

Tabla de verdad (8 filas)

Mayoría de tres (votación 2 de 3): tabla de verdad, mapa de Karnaugh y forma NAND
#ABCmajority
0FALSOFALSOFALSOFALSO
1FALSOFALSOVERDADEROFALSO
2FALSOVERDADEROFALSOFALSO
3FALSOVERDADEROVERDADEROVERDADERO
4VERDADEROFALSOFALSOFALSO
5VERDADEROFALSOVERDADEROVERDADERO
6VERDADEROVERDADEROFALSOVERDADERO
7VERDADEROVERDADEROVERDADEROVERDADERO

Lectura en lenguaje claro

Principiantemajority es verdadero exactamente cuando se cumple al menos una de las condiciones siguientes (pueden cumplirse varias):
1. A y B son ambos verdaderos
2. A y C son ambos verdaderos
3. B y C son ambos verdaderos
En todos los demás casos, majority es falso.
Sobre los operadores:
- OR (O) es inclusivo: es verdadero en cuanto al menos una parte es verdadera, también cuando lo son varias.
- AND (Y) solo es verdadero cuando todas sus partes son verdaderas.
Intermediomajority es verdadero exactamente cuando se cumple al menos una de las condiciones siguientes (pueden cumplirse varias):
1. A y B son ambos verdaderos
2. A y C son ambos verdaderos
3. B y C son ambos verdaderos
En todos los demás casos, majority es falso.
Avanzadomajority es verdadero exactamente cuando se cumple al menos una de las condiciones siguientes (pueden cumplirse varias) [disyunción inclusiva ∨]:
1. A y B son ambos verdaderos [conjunción ∧]
2. A y C son ambos verdaderos [conjunción ∧]
3. B y C son ambos verdaderos [conjunción ∧]
En todos los demás casos, majority es falso.
Notación formal: (A ∧ B) ∨ (A ∧ C) ∨ (B ∧ C)

Diagrama lógico

Majority of three (2-out-of-3 voting): truth table, K-map and NAND form Majority of three (2-out-of-3 voting): truth table, K-map and NAND form A B C majority OR AND AND AND
Majority of three (2-out-of-3 voting): truth table, K-map and NAND form Majority of three (2-out-of-3 voting): truth table, K-map and NAND form A B C majority OR AND AND AND

Simplificación paso a paso

El motor no encontró ninguna ley que acorte esta expresión; ya es tan corta como sus leyes de reescritura permiten.

(A AND B) OR (A AND C) OR (B AND C)

Mapa de Karnaugh

A \ BC
00
01
11
10
0
0m0
0m1
1m3
0m2
1
0m4
1m5
1m7
1m6
  1. celdas m6, m7A AND B
  2. celdas m5, m7A AND C
  3. celdas m3, m7B AND C
(A AND B) OR (A AND C) OR (B AND C) · Derived (A AND B) OR (A AND C) OR (B AND C). Exactly equivalent on every assignment.

Mintérminos y maxtérminos

majority(A, B, C) = Σm(3, 5, 6, 7)majority(A, B, C) = ΠM(0, 1, 2, 4)

Orden de variables: A, B, C · 8 filas

Formas normales

Forma normal conjuntiva (FNC)

(A OR B) AND (A OR C) AND (B OR C)

3 cláusulas, 6 literales · complete · Distributividad ×2, Absorción ×2, Idempotencia ×1

Forma normal disyuntiva (FND)

(A AND B) OR (A AND C) OR (B AND C)

3 términos, 6 literales · complete

Solo NAND, solo NOR

Forma solo con NAND

NAND(NAND(NAND(NAND(A, B), NAND(A, C)), NAND(NAND(A, B), NAND(A, C))), NAND(B, C))

9 compuertas · equivalencia verificada en todas las filas

Forma solo con NOR

NOR(NOR(NOR(NOR(NOR(NOR(A, A), NOR(B, B)), NOR(NOR(A, A), NOR(C, C))), NOR(NOR(NOR(A, A), NOR(B, B)), NOR(NOR(A, A), NOR(C, C)))), NOR(NOR(B, B), NOR(C, C))), NOR(NOR(NOR(NOR(NOR(A, A), NOR(B, B)), NOR(NOR(A, A), NOR(C, C))), NOR(NOR(NOR(A, A), NOR(B, B)), NOR(NOR(A, A), NOR(C, C)))), NOR(NOR(B, B), NOR(C, C))))

39 compuertas · equivalencia verificada en todas las filas

La misma regla como código

Python
# -*- coding: utf-8 -*-
# Generated by Tangibool (tangibool.python/1). Do not edit by hand; regenerate from the source revision.
# Model: not stated
# Source revision: reference
# Interpretation status: not stated
"""Tangibool evaluator (decision model).

Generated deterministically from the validated Boolean model; it evaluates exactly that
model. It does not establish that the model is a complete, legal, or safe statement of a
real-world rule, and evaluating examples does not verify the rule.

Source revision: reference
Interpretation status: not stated
Exporter: 1.0.0 (format tangibool.python/1; engine 1.0.0; semantics tangibool-semantics/1)
Logic digest: b7cf2f66ad74a4d23184d37a24dcffbc8278c9909728a0c4872e824905513fe8
Assumptions digest: d58ee1ad38e23e5093e4baa1047b5ae70d6972e08f555e34ac3fa16df63c4a78

Inputs (dict keys, declared order) and generated parameter names:
    'A' -> input_A
    'B' -> input_B
    'C' -> input_C

Outputs (declared order) and their functions:
    'majority' -> output_majority(inputs)

Assumptions (the declared scope, checked by in_scope(inputs)):
    none; every complete assignment is in scope.

Input contract:
    Every required input must be exactly True or False (type(value) is bool). Missing
    inputs, None, strings, integers (including 0 and 1), and keys that are not declared
    inputs raise InputError before anything is evaluated, including inputs that a
    short-circuiting operator would never read. Results are always bool.

Scope:
    Decision functions raise OutOfScopeError when the inputs violate an assumption; an
    out-of-scope assignment is never turned into a False result. Pass check_scope=False
    to evaluate without the scope check, and use in_scope(inputs) to test it separately.

Usage:

    import tangibool_model as model

    model.evaluate({'A': False, 'B': False, 'C': False})
    # -> {'majority': False}
    model.output_majority({'A': False, 'B': False, 'C': False})
    # -> False
    model.evaluate({'A': 1, 'B': False, 'C': False})
    # raises InputError: 1 is an int, not a bool
"""

import collections.abc as _abc
from typing import Dict, Mapping, Tuple

__all__ = [
    "MODEL_INFO",
    "IDENTIFIER_MAP",
    "INPUT_NAMES",
    "OUTPUT_NAMES",
    "ASSUMPTIONS",
    "InputError",
    "OutOfScopeError",
    "minterm_index",
    "in_scope",
    "evaluate",
    "output_majority",
]

MODEL_INFO = {
    "format": "tangibool.python/1",
    "mode": "decision",
    "model": None,
    "revision": "reference",
    "interpretation": None,
    "exporter": "1.0.0",
    "engine_version": "1.0.0",
    "semantics_version": "tangibool-semantics/1",
    "logic_digest": "b7cf2f66ad74a4d23184d37a24dcffbc8278c9909728a0c4872e824905513fe8",
    "assumptions_digest": "d58ee1ad38e23e5093e4baa1047b5ae70d6972e08f555e34ac3fa16df63c4a78",
    "primary_output": "majority",
    "unused_inputs": (),
    "subcircuits": (),
}

# Stable ID -> generated identifier (reversible mapping; names are exact, escaped strings).
IDENTIFIER_MAP = {
    "v_b45380ba34de": {"kind": "input", "name": "A", "identifier": "input_A"},
    "v_d43875bbafcf": {"kind": "input", "name": "B", "identifier": "input_B"},
    "v_d39fa64298ba": {"kind": "input", "name": "C", "identifier": "input_C"},
    "f_44f6cbf56b13": {"kind": "output", "name": "majority", "identifier": "output_majority"},
}

INPUT_NAMES = ("A", "B", "C")
OUTPUT_NAMES = ("majority",)
ASSUMPTIONS = ()

_DECLARED_INPUTS = frozenset(INPUT_NAMES)
_SCOPE_INPUTS = ()
_ASSUMPTION_FORMULAS = {entry["name"]: entry["formula"] for entry in ASSUMPTIONS}


class InputError(ValueError):
    """Raised when inputs are missing, undeclared, or not exactly True/False.

    Every required input must satisfy type(value) is bool. Missing inputs, None, strings,
    integers (including 0 and 1), and keys that are not declared inputs are rejected before
    anything is evaluated. A missing input is never treated as False. The individual problems
    are listed in the problems attribute.
    """

    def __init__(self, problems):
        self.problems = tuple(problems)
        super().__init__("Invalid inputs: " + "; ".join(self.problems))


class OutOfScopeError(ValueError):
    """Raised when the inputs violate the model's assumptions (its declared scope).

    Outside its assumptions the rule has no decision: this error is never a False result.
    The names of the violated assumptions are in the violated attribute.
    """

    def __init__(self, violated):
        self.violated = tuple(violated)
        details = ", ".join(name + " (" + _ASSUMPTION_FORMULAS.get(name, "?") + ")" for name in self.violated)
        super().__init__(
            "Out of scope: the inputs violate "
            + ("assumption " if len(self.violated) == 1 else "assumptions ")
            + details
            + ". The rule has no decision outside its assumptions; this is not a False result."
        )


def _short_repr(value: object) -> str:
    text = repr(value)
    return text if len(text) <= 60 else text[:57] + "..."


def _checked_inputs(inputs: Mapping[str, bool], required: Tuple[str, ...], check_scope: bool) -> Dict[str, bool]:
    """Validate inputs strictly before anything is evaluated and return a plain copy."""
    if type(check_scope) is not bool:
        raise TypeError("check_scope must be True or False")
    if not isinstance(inputs, _abc.Mapping):
        raise InputError(["inputs must be a mapping from input names to True/False, got " + type(inputs).__name__])
    problems = []
    for key in inputs:
        if type(key) is not str or key not in _DECLARED_INPUTS:
            declared = ", ".join(repr(name) for name in INPUT_NAMES) or "none"
            problems.append("undeclared input " + _short_repr(key) + " (declared inputs: " + declared + ")")
    needed = tuple(required) + (_SCOPE_INPUTS if check_scope else ())
    for name in needed:
        if name not in inputs:
            problems.append("missing required input " + repr(name))
    for key, value in inputs.items():
        if type(key) is str and key in _DECLARED_INPUTS and type(value) is not bool:
            problems.append(
                "input " + repr(key) + " must be True or False (type bool), got "
                + type(value).__name__ + " " + _short_repr(value)
            )
    if problems:
        raise InputError(list(dict.fromkeys(problems)))
    return dict(inputs.items())


def _require_bool_args(function: str, pairs: Tuple[Tuple[str, object], ...]) -> None:
    problems = [
        "argument " + repr(name) + " of " + function + " must be True or False (type bool), got "
        + type(value).__name__ + " " + _short_repr(value)
        for name, value in pairs
        if type(value) is not bool
    ]
    if problems:
        raise InputError(problems)


def minterm_index(*values: bool) -> int:
    """Row index of an assignment over a declared variable order.

    The first value is the most significant bit, so all-False is row 0. Used for indexed
    minterm (sum) and maxterm (product) forms.
    """
    index = 0
    for value in values:
        if type(value) is not bool:
            raise InputError(["minterm_index() takes True/False values, got " + type(value).__name__ + " " + _short_repr(value)])
        index = index * 2 + (1 if value else 0)
    return index


def _scope_values(values: Dict[str, bool]) -> Tuple[Tuple[str, bool], ...]:
    """Value of every enabled, confirmed assumption for validated inputs, in declared order."""
    return ()


def _require_in_scope(values: Dict[str, bool]) -> None:
    violated = tuple(name for name, holds in _scope_values(values) if not holds)
    if violated:
        raise OutOfScopeError(violated)


def in_scope(inputs: Mapping[str, bool]) -> bool:
    """True when the inputs satisfy every assumption (the model's declared scope).

    Requires the inputs the assumptions read; raises InputError for invalid inputs.
    """
    values = _checked_inputs(inputs, (), True)
    return all(holds for _, holds in _scope_values(values))


# ---- Formula bodies (inputs are validated by the public functions below) ----


def _compute_output_majority(input_A: bool, input_B: bool, input_C: bool) -> bool:
    """Decision output 'majority': (A AND B) OR (A AND C) OR (B AND C)"""
    return (input_A and input_B) or (input_A and input_C) or (input_B and input_C)


# ---- Public API ----


def output_majority(inputs: Mapping[str, bool], *, check_scope: bool = True) -> bool:
    """Decision output 'majority' (stable ID f_44f6cbf56b13).

    'majority' := (A AND B) OR (A AND C) OR (B AND C)

    Required inputs: 'A', 'B', 'C'.
    Raises InputError for missing, undeclared, or non-bool inputs, and OutOfScopeError
    when check_scope is True and the inputs violate an assumption.
    """
    values = _checked_inputs(inputs, ("A", "B", "C"), check_scope)
    if check_scope:
        _require_in_scope(values)
    output_majority_value = _compute_output_majority(values["A"], values["B"], values["C"])
    return output_majority_value


def evaluate(inputs: Mapping[str, bool], *, check_scope: bool = True) -> Dict[str, bool]:
    """Evaluate every output (declared order); each output is computed once.

    Required inputs: 'A', 'B', 'C'.
    Raises InputError for missing, undeclared, or non-bool inputs, and OutOfScopeError
    when check_scope is True and the inputs violate an assumption.
    """
    values = _checked_inputs(inputs, ("A", "B", "C"), check_scope)
    if check_scope:
        _require_in_scope(values)
    output_majority_value = _compute_output_majority(values["A"], values["B"], values["C"])
    return {
        "majority": output_majority_value,
    }
PostgreSQL
-- Tangibool PostgreSQL export (tangibool.postgresql/1)
-- Target: PostgreSQL 16 or later with typed boolean inputs; tested with PostgreSQL 18.3 (PGlite 0.5.8).
-- Not a claim of compatibility with other SQL dialects.
-- Model: not stated
-- Source revision: reference
-- Interpretation status: not stated
-- Exporter: 1.0.0 (engine 1.0.0; semantics tangibool-semantics/1)
-- Logic digest: b7cf2f66ad74a4d23184d37a24dcffbc8278c9909728a0c4872e824905513fe8
-- Assumptions digest: d58ee1ad38e23e5093e4baa1047b5ae70d6972e08f555e34ac3fa16df63c4a78
-- Mode: decision
--
-- Read-only: this file contains only WITH / VALUES / SELECT statements. No DDL, DML,
-- procedures, credentials, network access, or database changes. The expressions are pure
-- Boolean expressions, so their result does not depend on SQL evaluation order.
--
-- NON-NULL INPUT PRECONDITION: NULL is not a truth value of this rule. Every fragment below
-- is defined only when every input column it reads is a non-NULL boolean. The guard template
-- (section 2) marks any NULL input as 'invalid_input' and any row that violates the
-- assumptions as 'out_of_scope', and fills output columns only for 'ok' rows; a NULL in an
-- output column of another row is an envelope marker, not a third truth value. Never wrap
-- the fragments in COALESCE(..., FALSE) or otherwise choose a meaning for unknown inputs.
-- This evaluates the supplied model; it does not show that the model is a complete, legal,
-- or safe statement of a real-world rule.
--
-- Input columns (stable ID: name -> column):
--   v_b45380ba34de: A -> "in_A"
--   v_d43875bbafcf: B -> "in_B"
--   v_d39fa64298ba: C -> "in_C"
-- Output columns:
--   f_44f6cbf56b13: majority -> "out_majority"
-- Assumptions (scope K; exported separately and never folded into an output):
--   none; every complete input row is in scope.

-- ----------------------------------------------------------------------------------------------
-- 1. Expression fragments (parenthesised; non-NULL boolean inputs required)
-- ----------------------------------------------------------------------------------------------
--
-- [out_majority] output majority (stable ID f_44f6cbf56b13)
--   majority := (A AND B) OR (A AND C) OR (B AND C)
--   PRECONDITION: "in_A", "in_B", "in_C" are non-NULL booleans.
--   (("in_A" AND "in_B") OR ("in_A" AND "in_C") OR ("in_B" AND "in_C"))
--

-- ----------------------------------------------------------------------------------------------
-- 2. Guard template (read-only SELECT over an inputs list)
-- ----------------------------------------------------------------------------------------------
-- Replace the example rows between the markers with your own rows, or replace the inputs
-- CTE with a SELECT that provides the boolean columns listed in the header. status is
-- 'invalid_input' when any input is NULL, 'out_of_scope' when the assumptions are false, and
-- 'ok' otherwise; output columns are filled only for 'ok' rows (NULL elsewhere is an
-- envelope marker). Assumption columns are shown for rows with complete inputs.
WITH inputs ("row_id", "in_A", "in_B", "in_C") AS (
  -- tangibool:example-rows:begin
  VALUES
    (1, FALSE, FALSE, FALSE),
    (2, FALSE, FALSE, TRUE),
    (3, FALSE, TRUE, FALSE),
    (4, FALSE, TRUE, TRUE),
    (5, TRUE, FALSE, FALSE),
    (6, TRUE, FALSE, TRUE),
    (7, TRUE, TRUE, FALSE),
    (8, TRUE, TRUE, TRUE),
    (9, NULL::boolean, FALSE, FALSE)
  -- tangibool:example-rows:end
),
checked AS (
  SELECT
    inputs.*,
    CASE
      WHEN "in_A" IS NULL OR "in_B" IS NULL OR "in_C" IS NULL THEN 'invalid_input'
      ELSE 'ok'
    END AS "status"
  FROM inputs
)
SELECT
  "row_id",
  "in_A",
  "in_B",
  "in_C",
  "status",
  CASE WHEN "status" = 'ok' THEN (("in_A" AND "in_B") OR ("in_A" AND "in_C") OR ("in_B" AND "in_C")) END AS "out_majority"
FROM checked
ORDER BY "row_id";
SMT-LIB
; Tangibool SMT-LIB export (tangibool.smtlib/1)
; Profile: SMT-LIB 2.6 Boolean subset (QF_UF): Bool constants, define-fun, let, push/pop, assert, check-sat, echo.
; Tested with Z3 5.1.0 (z3-solver 5.2.0, WebAssembly build).
; Model: not stated
; Source revision: reference
; Interpretation status: not stated
; Exporter: 1.0.0 (engine 1.0.0; semantics tangibool-semantics/1)
; Logic digest: b7cf2f66ad74a4d23184d37a24dcffbc8278c9909728a0c4872e824905513fe8
; Assumptions digest: d58ee1ad38e23e5093e4baa1047b5ae70d6972e08f555e34ac3fa16df63c4a78
; Mode: decision
;
; Reading results: each query block states what sat and unsat mean for its question. A sat
; answer comes with a witness or counterexample (ask for it with (get-model) after sat only);
; unsat settles that scoped query and is solver-checked, not an independently checked proof
; certificate; unknown settles nothing. Blocks are scoped with push/pop, so assertions never
; accumulate across questions. This checks the supplied model, not whether it is a complete,
; legal, or safe statement of a real-world rule.
;
; Symbols (stable ID: name -> symbol):
;   v_b45380ba34de: A -> in_A
;   v_d43875bbafcf: B -> in_B
;   v_d39fa64298ba: C -> in_C
;   f_44f6cbf56b13: majority -> out_majority

(set-option :produce-models true)
(set-info :smt-lib-version 2.6)
(set-logic QF_UF)

; ---- Inputs (declared order)
(declare-const in_A Bool) ; A
(declare-const in_B Bool) ; B
(declare-const in_C Bool) ; C

; ---- Outputs (dependencies first)
; output majority (stable ID f_44f6cbf56b13): (A AND B) OR (A AND C) OR (B AND C)
(define-fun out_majority () Bool (or (and in_A in_B) (and in_A in_C) (and in_B in_C)))

; ---- Assumptions (the scope K; never folded into an output)
; K: conjunction of the enabled, confirmed assumptions (true when there are none)
(define-fun K () Bool true)

; ---- Definitions only: nothing is asserted and no check is run.
; Add (assert ...) and (check-sat) inside (push 1) ... (pop 1) to ask a question.
LaTeX
majority = \left(A \cdot B\right) + \left(A \cdot C\right) + \left(B \cdot C\right)

El error habitual

Esperar que el simplificador acorte la fórmula porque los tres términos se solapan. Se solapan, en la fila en la que los tres votan sí, pero quitar cualquier término pierde una de las filas con dos síes. La tabla muestra que las cuatro filas verdaderas solo sobreviven con los tres términos presentes.

Preguntas

¿Por qué la FNC tiene aquí el mismo tamaño que la FND?

La mayoría es autodual: intercambiar AND y OR devuelve la misma función. Así (A OR B) AND (A OR C) AND (B OR C) tiene tres cláusulas de dos literales, espejo exacto de los tres términos de dos literales de la FND, y la tabla de verdad confirma las dos formas en todas las filas.

¿Cómo se relaciona la forma NAND de 9 compuertas con la fórmula?

Cada par A AND B se convierte en un NAND, y el OR de los tres pares en un NAND de sus salidas, que necesita los inversores de entradas unidas habituales en la construcción mecánica. El conversor informa de 9 compuertas y vuelve a evaluar el resultado contra la tabla antes de mostrarlo.

Relacionado

Operadores y compuertas

Herramientas

Véase también

Ejemplos resueltos

Generado a partir del motor de Tangibool, semántica tangibool-semantics/1, motor 1.0.0, compilación . Cada tabla, mapa, simplificación y veredicto de estas páginas lo calculó el motor de Tangibool al compilar el sitio, y cada afirmación la volvió a comprobar el mismo verificador exacto que usa la app. Los límites se indican donde aplican. © 2026 Foreranger LTD.