Σm(1, 2, 4, 7): canonical sum of products for three variables
A function given by its minterm list, Σm(A, B, C; 1, 2, 4, 7), expanded by the converter into four three-literal terms. The table shows it is the odd-parity function, and the map confirms nothing merges.
Minterm notation names a function by the rows on which it is true: here rows 1, 2, 4 and 7 of the eight-row table over A, B and C, with A as the most significant bit. The engine's reading says exactly that, f is true when the row of (A, B, C) is one of 1, 2, 4 and 7. Written out, those rows are the ones with exactly one input true and the row with all three, so this is the parity function from the XOR pages, specified by enumeration instead of by operator.
The checks: not a tautology, counterexample A = FALSE, B = FALSE, C = FALSE; satisfiable, witness A = FALSE, B = FALSE, C = TRUE. The simplifier found no law to apply to a minterm list. The converter uses minterm expansion once: the DNF lists the four minterms as three-literal terms, twelve literals, and the CNF is the four-clause product over ΠM(0, 3, 5, 6), twelve literals as well. The Karnaugh map draws four single-cell groups, four prime implicants, and derives the same four terms. The gate converters report 59 NAND and 119 NOR for the expansion.
Minterm lists are how truth tables arrive from specifications, test logs and lookup tables: someone hands you the rows that should be true. The thing to watch is the variable order, which fixes what each number means; the page states A, B, C, and swapping the order renumbers every row. The expansion is exact but verbose, and when the function has structure, as this one does, the operator form is the one to keep.
f := Σm(A, B, C; 1, 2, 4, 7) · output
Exact checks
Truth table (8 rows)
| # | A | B | C | f |
|---|---|---|---|---|
| 0 | FALSE | FALSE | FALSE | FALSE |
| 1 | FALSE | FALSE | TRUE | TRUE |
| 2 | FALSE | TRUE | FALSE | TRUE |
| 3 | FALSE | TRUE | TRUE | FALSE |
| 4 | TRUE | FALSE | FALSE | TRUE |
| 5 | TRUE | FALSE | TRUE | FALSE |
| 6 | TRUE | TRUE | FALSE | FALSE |
| 7 | TRUE | TRUE | TRUE | TRUE |
Plain-language reading
Beginnerf is true exactly when the truth-table row of (A, B, C) is one of the rows 1, 2, 4, and 7.
In every other case, f is false.
About the operators:
- Σm lists the truth-table rows (minterms) where the formula is true. Rows are numbered from 0 with the first listed input as the most significant bit.
Intermediatef is true exactly when the truth-table row of (A, B, C) is one of the rows 1, 2, 4, and 7.
In every other case, f is false.
Advancedf is true exactly when the truth-table row of (A, B, C) is one of the rows 1, 2, 4, and 7 [canonical sum of minterms (DNF)].
In every other case, f is false.
Formal notation: Σm(A, B, C; 1, 2, 4, 7)
Logic diagram
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.
Σm(A, B, C; 1, 2, 4, 7)
Karnaugh map
- cells m1
NOT A AND NOT B AND C - cells m2
NOT A AND B AND NOT C - cells m4
A AND NOT B AND NOT C - cells m7
A AND B AND C
Minterms and maxterms
f(A, B, C) = Σm(1, 2, 4, 7)f(A, B, C) = ΠM(0, 3, 5, 6)Variable order: A, B, C · 8 rows
Normal forms
Conjunctive normal form (CNF)
(A OR B OR C) AND (A OR NOT B OR NOT C) AND (NOT A OR B OR NOT C) AND (NOT A OR NOT B OR C)4 clauses, 12 literals · complete · Minterm expansion ×1
Disjunctive normal form (DNF)
(A AND B AND C) OR (A AND NOT B AND NOT C) OR (NOT A AND B AND NOT C) OR (NOT A AND NOT B AND C)4 terms, 12 literals · complete · Minterm expansion ×1
NAND-only and NOR-only
NAND-only form
NAND(NAND(NAND(NAND(NAND(NAND(NAND(A, A), NAND(B, B)), NAND(NAND(A, A), NAND(B, B))), C), NAND(NAND(NAND(NAND(A, A), B), NAND(NAND(A, A), B)), NAND(C, C))), NAND(NAND(NAND(NAND(NAND(A, A), NAND(B, B)), NAND(NAND(A, A), NAND(B, B))), C), NAND(NAND(NAND(NAND(A, A), B), NAND(NAND(A, A), B)), NAND(C, C)))), NAND(NAND(NAND(NAND(NAND(A, NAND(B, B)), NAND(A, NAND(B, B))), NAND(C, C)), NAND(NAND(NAND(A, B), NAND(A, B)), C)), NAND(NAND(NAND(NAND(A, NAND(B, B)), NAND(A, NAND(B, B))), NAND(C, C)), NAND(NAND(NAND(A, B), NAND(A, B)), C))))59 gates · verified equivalent on every row
NOR-only form
NOR(NOR(NOR(NOR(NOR(NOR(NOR(A, B), NOR(A, B)), NOR(C, C)), NOR(NOR(NOR(A, NOR(B, B)), NOR(A, NOR(B, B))), C)), NOR(NOR(NOR(NOR(A, B), NOR(A, B)), NOR(C, C)), NOR(NOR(NOR(A, NOR(B, B)), NOR(A, NOR(B, B))), C))), NOR(NOR(NOR(NOR(NOR(NOR(A, A), B), NOR(NOR(A, A), B)), C), NOR(NOR(NOR(NOR(A, A), NOR(B, B)), NOR(NOR(A, A), NOR(B, B))), NOR(C, C))), NOR(NOR(NOR(NOR(NOR(A, A), B), NOR(NOR(A, A), B)), C), NOR(NOR(NOR(NOR(A, A), NOR(B, B)), NOR(NOR(A, A), NOR(B, B))), NOR(C, C))))), NOR(NOR(NOR(NOR(NOR(NOR(A, B), NOR(A, B)), NOR(C, C)), NOR(NOR(NOR(A, NOR(B, B)), NOR(A, NOR(B, B))), C)), NOR(NOR(NOR(NOR(A, B), NOR(A, B)), NOR(C, C)), NOR(NOR(NOR(A, NOR(B, B)), NOR(A, NOR(B, B))), C))), NOR(NOR(NOR(NOR(NOR(NOR(A, A), B), NOR(NOR(A, A), B)), C), NOR(NOR(NOR(NOR(A, A), NOR(B, B)), NOR(NOR(A, A), NOR(B, B))), NOR(C, C))), NOR(NOR(NOR(NOR(NOR(A, A), B), NOR(NOR(A, A), B)), C), NOR(NOR(NOR(NOR(A, A), NOR(B, B)), NOR(NOR(A, A), NOR(B, B))), NOR(C, C))))))119 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: a6761edcac26b7dadbae062d60f0f1f0c3e599fd89612ae057d6479e2f8f840f
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:
'f' -> output_f(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})
# -> {'f': False}
model.output_f({'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_f",
]
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": "a6761edcac26b7dadbae062d60f0f1f0c3e599fd89612ae057d6479e2f8f840f",
"assumptions_digest": "d58ee1ad38e23e5093e4baa1047b5ae70d6972e08f555e34ac3fa16df63c4a78",
"primary_output": "f",
"unused_inputs": (),
"subcircuits": (),
}
# Stable ID -> generated identifier (reversible mapping; names are exact, escaped strings).
IDENTIFIER_MAP = {
"v_546c0eea250f": {"kind": "input", "name": "A", "identifier": "input_A"},
"v_fd4990008157": {"kind": "input", "name": "B", "identifier": "input_B"},
"v_e6f172f124a4": {"kind": "input", "name": "C", "identifier": "input_C"},
"f_d954e0bccf2a": {"kind": "output", "name": "f", "identifier": "output_f"},
}
INPUT_NAMES = ("A", "B", "C")
OUTPUT_NAMES = ("f",)
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_f(input_A: bool, input_B: bool, input_C: bool) -> bool:
"""Decision output 'f': \u03a3m(A, B, C; 1, 2, 4, 7)"""
return minterm_index(input_A, input_B, input_C) in (1, 2, 4, 7)
# ---- Public API ----
def output_f(inputs: Mapping[str, bool], *, check_scope: bool = True) -> bool:
"""Decision output 'f' (stable ID f_d954e0bccf2a).
'f' := \u03a3m(A, B, C; 1, 2, 4, 7)
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_f_value = _compute_output_f(values["A"], values["B"], values["C"])
return output_f_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_f_value = _compute_output_f(values["A"], values["B"], values["C"])
return {
"f": output_f_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: a6761edcac26b7dadbae062d60f0f1f0c3e599fd89612ae057d6479e2f8f840f
-- 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_546c0eea250f: A -> "in_A"
-- v_fd4990008157: B -> "in_B"
-- v_e6f172f124a4: C -> "in_C"
-- Output columns:
-- f_d954e0bccf2a: f -> "out_f"
-- 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_f] output f (stable ID f_d954e0bccf2a)
-- f := \u03a3m(A, B, C; 1, 2, 4, 7)
-- PRECONDITION: "in_A", "in_B", "in_C" are non-NULL booleans.
-- (((NOT "in_A") AND (NOT "in_B") AND "in_C") OR ((NOT "in_A") AND "in_B" AND (NOT "in_C")) OR ("in_A" AND (NOT "in_B") AND (NOT "in_C")) OR ("in_A" AND "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 (((NOT "in_A") AND (NOT "in_B") AND "in_C") OR ((NOT "in_A") AND "in_B" AND (NOT "in_C")) OR ("in_A" AND (NOT "in_B") AND (NOT "in_C")) OR ("in_A" AND "in_B" AND "in_C")) END AS "out_f"
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: a6761edcac26b7dadbae062d60f0f1f0c3e599fd89612ae057d6479e2f8f840f ; 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_546c0eea250f: A -> in_A ; v_fd4990008157: B -> in_B ; v_e6f172f124a4: C -> in_C ; f_d954e0bccf2a: f -> out_f (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 f (stable ID f_d954e0bccf2a): \u03a3m(A, B, C; 1, 2, 4, 7) (define-fun out_f () Bool (or (and (not in_A) (not in_B) in_C) (and (not in_A) in_B (not in_C)) (and in_A (not in_B) (not in_C)) (and in_A 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
f = \sum m_{(A, B, C)}(1, 2, 4, 7)The common slip
Reading Σm(1, 2, 4, 7) with the wrong bit order. With A as the most significant bit, row 4 is A = TRUE, B = FALSE, C = FALSE; with C as most significant it would be a different row. The page fixes the order as (A, B, C), and the table shows row 0 as all FALSE.
Questions
Is this the same function as A XOR B XOR C?
Its column matches the parity page's column, true on rows 1, 2, 4 and 7, and the four-term DNF is identical. The engine does not perform that identification here; you can confirm it with the equivalence checker by entering both formulas side by side.
Why so many gates for a four-term function?
The converters build the expanded sum of products with every literal spelled out and every inverter duplicated, and report what that construction costs: 59 NAND, 119 NOR. The XOR form of the same function, on the parity page, builds with 20 and 41.
Related
Tools
- Truth table generator: any Boolean expression, up to 12 variables, with intermediate columns
- Boolean algebra calculator and simplifier with steps (every law named and verified)
- Karnaugh map solver: 2 to 4 variables, groups, SOP and POS, don’t-cares from assumptions
See also
- Minterm: meaning and examples
- Minterm expansion: the canonical sum of products (Σm)
- Odd parity of three inputs: A XOR B XOR C
- Minterms vs maxterms
- Sum of products (SOP): meaning and examples
- Four-variable K-map: Σm(0, 2, 5, 7, 8, 10, 13, 15) simplified
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.