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Free shipping rule: (over_50 OR prime) AND NOT oversized AND domestic

A shipping rule, (over_50 OR prime) AND NOT oversized AND domestic: sixteen rows with three qualifying ones, a two-term DNF, and a NOR form of 7 gates against 25 NAND.

Shipping is free for orders over fifty or for prime customers, provided the parcel is not oversized and the address is domestic. The engine's reading lists the three requirements: at least one of over_50 or prime, oversized false, domestic true. On the sixteen-row table the output is true on three rows, Σm(5, 9, 13): prime only, over fifty only, or both, each with a normal-sized parcel going to a domestic address.

The checks: not a tautology, counterexample all four inputs FALSE; satisfiable, witness over_50 = FALSE, prime = TRUE, oversized = FALSE, domestic = TRUE. The simplifier found no law that shortens the four-operator rule; the CNF converter returns it unchanged as three clauses. The DNF converter applies distribution twice and gives (over_50 AND NOT oversized AND domestic) OR (prime AND NOT oversized AND domestic), two terms and six literals; the Karnaugh map derives the same from two groups, two prime implicants. The gate counts are 25 NAND and 7 NOR, the usual lopsidedness for an OR feeding an AND with a negated input.

Checkout rules of this shape are rewritten often, as promotions come and go, and each rewrite is a chance to change the three true rows by accident. The thing to watch is the two blockers: oversized is negated and domestic is not, and the two are easy to swap when the rule is transcribed into a pricing engine. The witness row, a prime customer with a normal domestic parcel, is a good smoke test, and the three true rows together are the complete positive suite.

free_shipping := (over_50 OR prime) AND NOT oversized AND domestic · output

Exact checks

Always true (tautology)? No Counterexample: over_50 = F, prime = F, oversized = F, domestic = F · Exhaustively checked and solver cross-checked · 1 rows
Always false (contradiction)? No Counterexample: over_50 = F, prime = T, oversized = F, domestic = T · Exhaustively checked and solver cross-checked · 6 rows
Can be true? Yes Example assignment: over_50 = F, prime = T, oversized = F, domestic = T · Exhaustively checked and solver cross-checked · 6 rows

Truth table (16 rows)

Free shipping rule: (over_50 OR prime) AND NOT oversized AND domestic
#over_50primeoversizeddomesticfree_shipping
0FALSEFALSEFALSEFALSEFALSE
1FALSEFALSEFALSETRUEFALSE
2FALSEFALSETRUEFALSEFALSE
3FALSEFALSETRUETRUEFALSE
4FALSETRUEFALSEFALSEFALSE
5FALSETRUEFALSETRUETRUE
6FALSETRUETRUEFALSEFALSE
7FALSETRUETRUETRUEFALSE
8TRUEFALSEFALSEFALSEFALSE
9TRUEFALSEFALSETRUETRUE
10TRUEFALSETRUEFALSEFALSE
11TRUEFALSETRUETRUEFALSE
12TRUETRUEFALSEFALSEFALSE
13TRUETRUEFALSETRUETRUE
14TRUETRUETRUEFALSEFALSE
15TRUETRUETRUETRUEFALSE

Plain-language reading

Beginnerfree_shipping is true exactly when all of the following hold:
1. at least one of over_50 or prime is true (both may be true)
2. oversized is false
3. domestic is true
In every other case, free_shipping is false.
About the operators:
- AND is true only when all of its parts are true.
- OR is inclusive: it is true when at least one part is true, including when several are.
- NOT reverses a value: true becomes false and false becomes true.
Intermediatefree_shipping is true exactly when all of the following hold:
1. at least one of over_50 or prime is true (both may be true)
2. oversized is false
3. domestic is true
In every other case, free_shipping is false.
Advancedfree_shipping is true exactly when all of the following hold [conjunction ∧]:
1. at least one of over_50 or prime is true (both may be true) [inclusive disjunction ∨]
2. oversized is false [negation ¬]
3. domestic is true
In every other case, free_shipping is false.
Formal notation: (over_50 ∨ prime) ∧ ¬oversized ∧ domestic

Logic diagram

Free shipping rule: (over_50 OR prime) AND NOT oversized AND domestic Free shipping rule: (over_50 OR prime) AND NOT oversized AND domestic over_50 prime oversized domestic free_shipping AND OR NOT
Free shipping rule: (over_50 OR prime) AND NOT oversized AND domestic Free shipping rule: (over_50 OR prime) AND NOT oversized AND domestic over_50 prime oversized domestic free_shipping AND OR NOT

Simplification, step by step

The engine found no law that shortens this expression; it is already as short as its rewriting laws can make it.

(over_50 OR prime) AND NOT oversized AND domestic

Karnaugh map

over_50prime \ oversizeddomestic
00
01
11
10
00
0m0
0m1
0m3
0m2
01
0m4
1m5
0m7
0m6
11
0m12
1m13
0m15
0m14
10
0m8
1m9
0m11
0m10
  1. cells m9, m13over_50 AND NOT oversized AND domestic
  2. cells m5, m13prime AND NOT oversized AND domestic
(over_50 AND NOT oversized AND domestic) OR (prime AND NOT oversized AND domestic) · Derived (over_50 AND NOT oversized AND domestic) OR (prime AND NOT oversized AND domestic). Exactly equivalent on every assignment.

Minterms and maxterms

free_shipping(over_50, prime, oversized, domestic) = Σm(5, 9, 13)free_shipping(over_50, prime, oversized, domestic) = ΠM(0, 1, 2, 3, 4, 6, 7, 8, 10, 11, 12, 14, 15)

Variable order: over_50, prime, oversized, domestic · 16 rows

Normal forms

Conjunctive normal form (CNF)

(over_50 OR prime) AND NOT oversized AND domestic

3 clauses, 4 literals · complete

Disjunctive normal form (DNF)

(over_50 AND NOT oversized AND domestic) OR (prime AND NOT oversized AND domestic)

2 terms, 6 literals · complete · Distribution ×2

NAND-only and NOR-only

NAND-only form

NAND(NAND(NAND(NAND(NAND(NAND(over_50, over_50), NAND(prime, prime)), NAND(oversized, oversized)), NAND(NAND(NAND(over_50, over_50), NAND(prime, prime)), NAND(oversized, oversized))), domestic), NAND(NAND(NAND(NAND(NAND(over_50, over_50), NAND(prime, prime)), NAND(oversized, oversized)), NAND(NAND(NAND(over_50, over_50), NAND(prime, prime)), NAND(oversized, oversized))), domestic))

25 gates · verified equivalent on every row

NOR-only form

NOR(NOR(NOR(NOR(over_50, prime), oversized), NOR(NOR(over_50, prime), oversized)), NOR(domestic, domestic))

7 gates · verified equivalent on every row

The same rule as code

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: 06b94ace715e24da7f488742835d4637399ac84b8c8d35b085821515e815163c
Assumptions digest: d58ee1ad38e23e5093e4baa1047b5ae70d6972e08f555e34ac3fa16df63c4a78

Inputs (dict keys, declared order) and generated parameter names:
    'over_50' -> input_over_50
    'prime' -> input_prime
    'oversized' -> input_oversized
    'domestic' -> input_domestic

Outputs (declared order) and their functions:
    'free_shipping' -> output_free_shipping(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({'over_50': False, 'prime': False, 'oversized': False, 'domestic': False})
    # -> {'free_shipping': False}
    model.output_free_shipping({'over_50': False, 'prime': False, 'oversized': False, 'domestic': False})
    # -> False
    model.evaluate({'over_50': 1, 'prime': False, 'oversized': False, 'domestic': 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_free_shipping",
]

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": "06b94ace715e24da7f488742835d4637399ac84b8c8d35b085821515e815163c",
    "assumptions_digest": "d58ee1ad38e23e5093e4baa1047b5ae70d6972e08f555e34ac3fa16df63c4a78",
    "primary_output": "free_shipping",
    "unused_inputs": (),
    "subcircuits": (),
}

# Stable ID -> generated identifier (reversible mapping; names are exact, escaped strings).
IDENTIFIER_MAP = {
    "v_c5a612b01b69": {"kind": "input", "name": "over_50", "identifier": "input_over_50"},
    "v_f6de1dea7c06": {"kind": "input", "name": "prime", "identifier": "input_prime"},
    "v_5f92878a5d47": {"kind": "input", "name": "oversized", "identifier": "input_oversized"},
    "v_edf6f5fd2f11": {"kind": "input", "name": "domestic", "identifier": "input_domestic"},
    "f_075d3af2c11d": {"kind": "output", "name": "free_shipping", "identifier": "output_free_shipping"},
}

INPUT_NAMES = ("over_50", "prime", "oversized", "domestic")
OUTPUT_NAMES = ("free_shipping",)
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_free_shipping(input_over_50: bool, input_prime: bool, input_oversized: bool, input_domestic: bool) -> bool:
    """Decision output 'free_shipping': (over_50 OR prime) AND NOT oversized AND domestic"""
    return (input_over_50 or input_prime) and (not input_oversized) and input_domestic


# ---- Public API ----


def output_free_shipping(inputs: Mapping[str, bool], *, check_scope: bool = True) -> bool:
    """Decision output 'free_shipping' (stable ID f_075d3af2c11d).

    'free_shipping' := (over_50 OR prime) AND NOT oversized AND domestic

    Required inputs: 'over_50', 'prime', 'oversized', 'domestic'.
    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, ("over_50", "prime", "oversized", "domestic"), check_scope)
    if check_scope:
        _require_in_scope(values)
    output_free_shipping_value = _compute_output_free_shipping(values["over_50"], values["prime"], values["oversized"], values["domestic"])
    return output_free_shipping_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: 'over_50', 'prime', 'oversized', 'domestic'.
    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, ("over_50", "prime", "oversized", "domestic"), check_scope)
    if check_scope:
        _require_in_scope(values)
    output_free_shipping_value = _compute_output_free_shipping(values["over_50"], values["prime"], values["oversized"], values["domestic"])
    return {
        "free_shipping": output_free_shipping_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: 06b94ace715e24da7f488742835d4637399ac84b8c8d35b085821515e815163c
-- 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_c5a612b01b69: over_50 -> "in_over_50"
--   v_f6de1dea7c06: prime -> "in_prime"
--   v_5f92878a5d47: oversized -> "in_oversized"
--   v_edf6f5fd2f11: domestic -> "in_domestic"
-- Output columns:
--   f_075d3af2c11d: free_shipping -> "out_free_shipping"
-- 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_free_shipping] output free_shipping (stable ID f_075d3af2c11d)
--   free_shipping := (over_50 OR prime) AND NOT oversized AND domestic
--   PRECONDITION: "in_over_50", "in_prime", "in_oversized", "in_domestic" are non-NULL booleans.
--   (("in_over_50" OR "in_prime") AND (NOT "in_oversized") AND "in_domestic")
--

-- ----------------------------------------------------------------------------------------------
-- 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_over_50", "in_prime", "in_oversized", "in_domestic") AS (
  -- tangibool:example-rows:begin
  VALUES
    (1, FALSE, FALSE, FALSE, FALSE),
    (2, FALSE, FALSE, FALSE, TRUE),
    (3, FALSE, FALSE, TRUE, FALSE),
    (4, FALSE, FALSE, TRUE, TRUE),
    (5, FALSE, TRUE, FALSE, FALSE),
    (6, FALSE, TRUE, FALSE, TRUE),
    (7, FALSE, TRUE, TRUE, FALSE),
    (8, FALSE, TRUE, TRUE, TRUE),
    (9, TRUE, FALSE, FALSE, FALSE),
    (10, TRUE, FALSE, FALSE, TRUE),
    (11, TRUE, FALSE, TRUE, FALSE),
    (12, TRUE, FALSE, TRUE, TRUE),
    (13, TRUE, TRUE, FALSE, FALSE),
    (14, TRUE, TRUE, FALSE, TRUE),
    (15, TRUE, TRUE, TRUE, FALSE),
    (16, TRUE, TRUE, TRUE, TRUE),
    (17, NULL::boolean, FALSE, FALSE, FALSE)
  -- tangibool:example-rows:end
),
checked AS (
  SELECT
    inputs.*,
    CASE
      WHEN "in_over_50" IS NULL OR "in_prime" IS NULL OR "in_oversized" IS NULL OR "in_domestic" IS NULL THEN 'invalid_input'
      ELSE 'ok'
    END AS "status"
  FROM inputs
)
SELECT
  "row_id",
  "in_over_50",
  "in_prime",
  "in_oversized",
  "in_domestic",
  "status",
  CASE WHEN "status" = 'ok' THEN (("in_over_50" OR "in_prime") AND (NOT "in_oversized") AND "in_domestic") END AS "out_free_shipping"
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: 06b94ace715e24da7f488742835d4637399ac84b8c8d35b085821515e815163c
; 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_c5a612b01b69: over_50 -> in_over_50
;   v_f6de1dea7c06: prime -> in_prime
;   v_5f92878a5d47: oversized -> in_oversized
;   v_edf6f5fd2f11: domestic -> in_domestic
;   f_075d3af2c11d: free_shipping -> out_free_shipping

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

; ---- Inputs (declared order)
(declare-const in_over_50 Bool) ; over_50
(declare-const in_prime Bool) ; prime
(declare-const in_oversized Bool) ; oversized
(declare-const in_domestic Bool) ; domestic

; ---- Outputs (dependencies first)
; output free_shipping (stable ID f_075d3af2c11d): (over_50 OR prime) AND NOT oversized AND domestic
(define-fun out_free_shipping () Bool (and (or in_over_50 in_prime) (not in_oversized) in_domestic))

; ---- 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
free_shipping = \left(\mathit{over\_50} + \mathit{prime}\right) \cdot \overline{\mathit{oversized}} \cdot \mathit{domestic}

The common slip

Transcribing the two blockers with the same polarity, NOT oversized AND NOT domestic or oversized AND domestic. Either version changes all three qualifying rows. The table's true rows all have oversized = FALSE and domestic = TRUE; checking that pair is the quickest review of any reimplementation.

Questions

Why are the minterm numbers 5, 9 and 13?

With over_50 as the most significant bit and domestic as the least, a qualifying row ends in the bits oversized = 0, domestic = 1, which contributes 1, and starts with prime alone, 4, over_50 alone, 8, or both, 12. The three sums are 5, 9 and 13.

Related

Operators and gates

Tools

See also

Worked examples

Generated from the Tangibool engine, semantics tangibool-semantics/1, engine 1.0.0, build . Every table, map, simplification and verdict on these pages was computed by the Tangibool engine when the site was built, and every claim was re-checked by the same exact checker the app uses. Limits are stated where they apply. © 2026 Foreranger LTD.