Multiplexor 2 a 1: (S AND B) OR (NOT S AND A)
Un multiplexor 2 a 1, (S AND B) OR (NOT S AND A): S elige B si es verdadera y A si es falsa. La tabla, una FNC con cláusula de consenso, un mapa que lista tres implicantes primos pero solo necesita dos y una forma NAND de 4 compuertas.
El glosario nombra las partes: S es la línea de selección, A la entrada elegida cuando S es FALSO y B la elegida cuando S es VERDADERO. La fórmula es un OR de los dos casos, cada uno un AND de la condición de selección con su entrada de datos. La lectura del motor dice que out es verdadero exactamente cuando S y B son ambos verdaderos, o S es falso y A es verdadero. En la tabla de ocho filas sobre (S, B, A) la salida es verdadera en Σm(1, 3, 6, 7): las filas en que la entrada elegida vale 1.
Las comprobaciones: tautología violada con S = FALSO, B = FALSO, A = FALSO, satisfacible con el testigo S = FALSO, B = FALSO, A = VERDADERO. El simplificador no encontró ninguna ley aplicable a los cuatro operadores, y la FND es la original. La FNC, tras una distributividad y un complemento, es (S OR A) AND (NOT S OR B) AND (B OR A): la tercera cláusula es el consenso de las dos primeras. El mapa de Karnaugh informa de tres implicantes primos pero cubre todos los unos con dos, S AND B y NOT S AND A, y deriva la original. Compuertas: 4 NAND, 13 NOR.
El multiplexor es el «si… entonces… si no» del hardware y el operador ternario del software: S ? B : A. Toda tabla de consulta, todo conmutador de bus y toda asignación condicional es un multiplexor o un árbol de ellos. Lo que hay que vigilar en código es la selección invertida: intercambiar A y B selecciona en silencio la entrada equivocada en todas las filas, y ninguna prueba aislada lo detecta salvo que fije S en los dos sentidos. La cláusula (B OR A) de la FNC recuerda además que la salida es siempre 1 cuando las dos entradas de datos son 1, haga lo que haga S.
S: la línea de selección; A: entrada elegida cuando S es FALSO; B: entrada elegida cuando S es VERDADERO;
out := (S AND B) OR (NOT S AND A) · salida
Comprobaciones exactas
Tabla de verdad (8 filas)
| # | S | B | A | out |
|---|---|---|---|---|
| 0 | FALSO | FALSO | FALSO | FALSO |
| 1 | FALSO | FALSO | VERDADERO | VERDADERO |
| 2 | FALSO | VERDADERO | FALSO | FALSO |
| 3 | FALSO | VERDADERO | VERDADERO | VERDADERO |
| 4 | VERDADERO | FALSO | FALSO | FALSO |
| 5 | VERDADERO | FALSO | VERDADERO | FALSO |
| 6 | VERDADERO | VERDADERO | FALSO | VERDADERO |
| 7 | VERDADERO | VERDADERO | VERDADERO | VERDADERO |
Lectura en lenguaje claro
Principianteout es verdadero exactamente cuando se cumple al menos una de las condiciones siguientes (pueden cumplirse ambas):
1. S y B son ambos verdaderos
2. S es falso y A es verdadero
En todos los demás casos, out 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.
- NOT (NO) invierte un valor: lo verdadero pasa a ser falso y lo falso, verdadero.
Intermedioout es verdadero exactamente cuando se cumple al menos una de las condiciones siguientes (pueden cumplirse ambas):
1. S y B son ambos verdaderos
2. S es falso y A es verdadero
En todos los demás casos, out es falso.
Avanzadoout es verdadero exactamente cuando se cumple al menos una de las condiciones siguientes (pueden cumplirse ambas) [disyunción inclusiva ∨]:
1. S y B son ambos verdaderos [conjunción ∧]
2. S es falso y A es verdadero [conjunción ∧]
En todos los demás casos, out es falso.
Notación formal: (S ∧ B) ∨ (¬S ∧ A)
Diagrama lógico
Simplificación paso a paso
El motor no encontró ninguna ley que acorte esta expresión; ya es tan corta como sus leyes de reescritura permiten.
(S AND B) OR (NOT S AND A)
Mapa de Karnaugh
- celdas m6, m7
S AND B - celdas m1, m3
NOT S AND A
Mintérminos y maxtérminos
out(S, B, A) = Σm(1, 3, 6, 7)out(S, B, A) = ΠM(0, 2, 4, 5)Orden de variables: S, B, A · 8 filas
Formas normales
Forma normal conjuntiva (FNC)
(S OR A) AND (NOT S OR B) AND (B OR A)3 cláusulas, 6 literales · complete · Distributividad ×1, Complemento ×1
Forma normal disyuntiva (FND)
(S AND B) OR (NOT S AND A)2 términos, 4 literales · complete
Solo NAND, solo NOR
Forma solo con NAND
NAND(NAND(S, B), NAND(NAND(S, S), A))4 compuertas · equivalencia verificada en todas las filas
Forma solo con NOR
NOR(NOR(NOR(NOR(S, S), NOR(B, B)), NOR(S, NOR(A, A))), NOR(NOR(NOR(S, S), NOR(B, B)), NOR(S, NOR(A, A))))13 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: 5ffeb83207427590b937d9e9351f148aa0882bcbda32ea058d245228c698157d
Assumptions digest: d58ee1ad38e23e5093e4baa1047b5ae70d6972e08f555e34ac3fa16df63c4a78
Inputs (dict keys, declared order) and generated parameter names:
'S' -> input_S
'B' -> input_B
'A' -> input_A
Outputs (declared order) and their functions:
'out' -> output_out(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({'S': False, 'B': False, 'A': False})
# -> {'out': False}
model.output_out({'S': False, 'B': False, 'A': False})
# -> False
model.evaluate({'S': 1, 'B': False, 'A': 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_out",
]
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": "5ffeb83207427590b937d9e9351f148aa0882bcbda32ea058d245228c698157d",
"assumptions_digest": "d58ee1ad38e23e5093e4baa1047b5ae70d6972e08f555e34ac3fa16df63c4a78",
"primary_output": "out",
"unused_inputs": (),
"subcircuits": (),
}
# Stable ID -> generated identifier (reversible mapping; names are exact, escaped strings).
IDENTIFIER_MAP = {
"v_12330a847fcb": {"kind": "input", "name": "S", "identifier": "input_S"},
"v_123e6af27a25": {"kind": "input", "name": "B", "identifier": "input_B"},
"v_43f56bcaef8c": {"kind": "input", "name": "A", "identifier": "input_A"},
"f_ae4d5262fa54": {"kind": "output", "name": "out", "identifier": "output_out"},
}
INPUT_NAMES = ("S", "B", "A")
OUTPUT_NAMES = ("out",)
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_out(input_S: bool, input_B: bool, input_A: bool) -> bool:
"""Decision output 'out': (S AND B) OR (NOT S AND A)"""
return (input_S and input_B) or ((not input_S) and input_A)
# ---- Public API ----
def output_out(inputs: Mapping[str, bool], *, check_scope: bool = True) -> bool:
"""Decision output 'out' (stable ID f_ae4d5262fa54).
'out' := (S AND B) OR (NOT S AND A)
Required inputs: 'S', 'B', 'A'.
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, ("S", "B", "A"), check_scope)
if check_scope:
_require_in_scope(values)
output_out_value = _compute_output_out(values["S"], values["B"], values["A"])
return output_out_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: 'S', 'B', 'A'.
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, ("S", "B", "A"), check_scope)
if check_scope:
_require_in_scope(values)
output_out_value = _compute_output_out(values["S"], values["B"], values["A"])
return {
"out": output_out_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: 5ffeb83207427590b937d9e9351f148aa0882bcbda32ea058d245228c698157d
-- 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_12330a847fcb: S -> "in_S"
-- v_123e6af27a25: B -> "in_B"
-- v_43f56bcaef8c: A -> "in_A"
-- Output columns:
-- f_ae4d5262fa54: out -> "out_out"
-- 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_out] output out (stable ID f_ae4d5262fa54)
-- out := (S AND B) OR (NOT S AND A)
-- PRECONDITION: "in_S", "in_B", "in_A" are non-NULL booleans.
-- (("in_S" AND "in_B") OR ((NOT "in_S") AND "in_A"))
--
-- ----------------------------------------------------------------------------------------------
-- 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_S", "in_B", "in_A") 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_S" IS NULL OR "in_B" IS NULL OR "in_A" IS NULL THEN 'invalid_input'
ELSE 'ok'
END AS "status"
FROM inputs
)
SELECT
"row_id",
"in_S",
"in_B",
"in_A",
"status",
CASE WHEN "status" = 'ok' THEN (("in_S" AND "in_B") OR ((NOT "in_S") AND "in_A")) END AS "out_out"
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: 5ffeb83207427590b937d9e9351f148aa0882bcbda32ea058d245228c698157d ; 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_12330a847fcb: S -> in_S ; v_123e6af27a25: B -> in_B ; v_43f56bcaef8c: A -> in_A ; f_ae4d5262fa54: out -> out_out (set-option :produce-models true) (set-info :smt-lib-version 2.6) (set-logic QF_UF) ; ---- Inputs (declared order) (declare-const in_S Bool) ; S (declare-const in_B Bool) ; B (declare-const in_A Bool) ; A ; ---- Outputs (dependencies first) ; output out (stable ID f_ae4d5262fa54): (S AND B) OR (NOT S AND A) (define-fun out_out () Bool (or (and in_S in_B) (and (not in_S) in_A))) ; ---- 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
out = \left(S \cdot B\right) + \left(\overline{S} \cdot A\right)El error habitual
Tratar el tercer implicante primo, el de B AND A, como un término necesario. El mapa lo lista, pero los dos grupos basados en la selección ya cubren los cuatro unos, así que la expresión derivada tiene dos términos. Añadir B AND A no cambia nada en la tabla; es un término de consenso redundante.
Preguntas
¿Por qué la forma NAND tiene solo 4 compuertas?
El multiplexor es un OR de dos AND, que es un NAND de dos NAND, más un NAND como inversor para NOT S: NAND(NAND(S, B), NAND(NAND(S, S), A)). El constructor NOR tiene que invertir más señales, y por eso informa de 13.
¿De dónde sale la cláusula (B OR A) de la FNC?
Distribuir el OR sobre los dos AND produce cuatro cláusulas; una contiene S OR NOT S y la elimina la ley del complemento, y (B OR A) se queda. Es el consenso de (S OR A) y (NOT S OR B), y la página del consenso explica por qué es redundante.
Relacionado
Operadores y compuertas
- Compuerta NOT (inversor): tabla de verdad, símbolo y el operador NOT
- Compuerta AND (puerta Y): tabla de verdad de 2, 3 y 4 entradas, símbolo y expresión
- Compuerta OR (puerta O): tabla de verdad de 2, 3 y 4 entradas
Herramientas
- Generador de tablas de verdad: cualquier expresión booleana, hasta 12 variables, con columnas intermedias
- Calculadora y simplificador de álgebra de Boole paso a paso (cada ley nombrada y verificada)
- Solucionador de mapas de Karnaugh: de 2 a 4 variables, agrupaciones, SOP y POS
Véase también
- Generador de circuitos lógicos: de expresión booleana a diagrama de compuertas (SVG)
- Teorema del consenso: AB + A'C + BC = AB + A'C, con demostración
- El consenso en la práctica: AB + A'C + BC simplificado
- Lógica combinacional: definición, ejemplo y equivalente en inglés
- Mayoría de tres (votación 2 de 3): tabla de verdad, mapa de Karnaugh y forma NAND
- Operadores lógicos en JavaScript: &&, ||, !, truthiness y precedencia
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.