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Type | Label | Description |
---|---|---|
Statement | ||
Theorem | nanbi12i 1501 | Join two logical equivalences with anti-conjunction. (Contributed by SF, 2-Jan-2018.) |
⊢ (𝜑 ↔ 𝜓) & ⊢ (𝜒 ↔ 𝜃) ⇒ ⊢ ((𝜑 ⊼ 𝜒) ↔ (𝜓 ⊼ 𝜃)) | ||
Theorem | nanbi1d 1502 | Introduce a right anti-conjunct to both sides of a logical equivalence. (Contributed by SF, 2-Jan-2018.) |
⊢ (𝜑 → (𝜓 ↔ 𝜒)) ⇒ ⊢ (𝜑 → ((𝜓 ⊼ 𝜃) ↔ (𝜒 ⊼ 𝜃))) | ||
Theorem | nanbi2d 1503 | Introduce a left anti-conjunct to both sides of a logical equivalence. (Contributed by SF, 2-Jan-2018.) |
⊢ (𝜑 → (𝜓 ↔ 𝜒)) ⇒ ⊢ (𝜑 → ((𝜃 ⊼ 𝜓) ↔ (𝜃 ⊼ 𝜒))) | ||
Theorem | nanbi12d 1504 | Join two logical equivalences with anti-conjunction. (Contributed by Scott Fenton, 2-Jan-2018.) |
⊢ (𝜑 → (𝜓 ↔ 𝜒)) & ⊢ (𝜑 → (𝜃 ↔ 𝜏)) ⇒ ⊢ (𝜑 → ((𝜓 ⊼ 𝜃) ↔ (𝜒 ⊼ 𝜏))) | ||
Theorem | nanass 1505 | A characterization of when an expression involving alternative denials associates. Remark: alternative denial is commutative, see nancom 1491. (Contributed by Richard Penner, 29-Feb-2020.) (Proof shortened by Wolf Lammen, 23-Oct-2022.) |
⊢ ((𝜑 ↔ 𝜒) ↔ (((𝜑 ⊼ 𝜓) ⊼ 𝜒) ↔ (𝜑 ⊼ (𝜓 ⊼ 𝜒)))) | ||
Syntax | wxo 1506 | Extend wff definition to include exclusive disjunction ("xor"). |
wff (𝜑 ⊻ 𝜓) | ||
Definition | df-xor 1507 | Define exclusive disjunction (logical "xor"). Return true if either the left or right, but not both, are true. After we define the constant true ⊤ (df-tru 1542) and the constant false ⊥ (df-fal 1552), we will be able to prove these truth table values: ((⊤ ⊻ ⊤) ↔ ⊥) (truxortru 1584), ((⊤ ⊻ ⊥) ↔ ⊤) (truxorfal 1585), ((⊥ ⊻ ⊤) ↔ ⊤) (falxortru 1586), and ((⊥ ⊻ ⊥) ↔ ⊥) (falxorfal 1587). Contrast with ∧ (df-an 397), ∨ (df-or 845), → (wi 4), and ⊼ (df-nan 1487). (Contributed by FL, 22-Nov-2010.) |
⊢ ((𝜑 ⊻ 𝜓) ↔ ¬ (𝜑 ↔ 𝜓)) | ||
Theorem | xnor 1508 | Two ways to write XNOR (exclusive not-or). (Contributed by Mario Carneiro, 4-Sep-2016.) |
⊢ ((𝜑 ↔ 𝜓) ↔ ¬ (𝜑 ⊻ 𝜓)) | ||
Theorem | xorcom 1509 | The connector ⊻ is commutative. (Contributed by Mario Carneiro, 4-Sep-2016.) (Proof shortened by Wolf Lammen, 21-Apr-2024.) |
⊢ ((𝜑 ⊻ 𝜓) ↔ (𝜓 ⊻ 𝜑)) | ||
Theorem | xorcomOLD 1510 | Obsolete version of xorcom 1509 as of 21-Apr-2024. (Contributed by Mario Carneiro, 4-Sep-2016.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ ((𝜑 ⊻ 𝜓) ↔ (𝜓 ⊻ 𝜑)) | ||
Theorem | xorass 1511 | The connector ⊻ is associative. (Contributed by FL, 22-Nov-2010.) (Proof shortened by Andrew Salmon, 8-Jun-2011.) (Proof shortened by Wolf Lammen, 20-Jun-2020.) |
⊢ (((𝜑 ⊻ 𝜓) ⊻ 𝜒) ↔ (𝜑 ⊻ (𝜓 ⊻ 𝜒))) | ||
Theorem | excxor 1512 | This tautology shows that xor is really exclusive. (Contributed by FL, 22-Nov-2010.) |
⊢ ((𝜑 ⊻ 𝜓) ↔ ((𝜑 ∧ ¬ 𝜓) ∨ (¬ 𝜑 ∧ 𝜓))) | ||
Theorem | xor2 1513 | Two ways to express "exclusive or". (Contributed by Mario Carneiro, 4-Sep-2016.) |
⊢ ((𝜑 ⊻ 𝜓) ↔ ((𝜑 ∨ 𝜓) ∧ ¬ (𝜑 ∧ 𝜓))) | ||
Theorem | xoror 1514 | Exclusive disjunction implies disjunction ("XOR implies OR"). (Contributed by BJ, 19-Apr-2019.) |
⊢ ((𝜑 ⊻ 𝜓) → (𝜑 ∨ 𝜓)) | ||
Theorem | xornan 1515 | Exclusive disjunction implies alternative denial ("XOR implies NAND"). (Contributed by BJ, 19-Apr-2019.) |
⊢ ((𝜑 ⊻ 𝜓) → ¬ (𝜑 ∧ 𝜓)) | ||
Theorem | xornan2 1516 | XOR implies NAND (written with the ⊼ connector). (Contributed by BJ, 19-Apr-2019.) |
⊢ ((𝜑 ⊻ 𝜓) → (𝜑 ⊼ 𝜓)) | ||
Theorem | xorneg2 1517 | The connector ⊻ is negated under negation of one argument. (Contributed by Mario Carneiro, 4-Sep-2016.) (Proof shortened by Wolf Lammen, 27-Jun-2020.) |
⊢ ((𝜑 ⊻ ¬ 𝜓) ↔ ¬ (𝜑 ⊻ 𝜓)) | ||
Theorem | xorneg1 1518 | The connector ⊻ is negated under negation of one argument. (Contributed by Mario Carneiro, 4-Sep-2016.) (Proof shortened by Wolf Lammen, 27-Jun-2020.) |
⊢ ((¬ 𝜑 ⊻ 𝜓) ↔ ¬ (𝜑 ⊻ 𝜓)) | ||
Theorem | xorneg 1519 | The connector ⊻ is unchanged under negation of both arguments. (Contributed by Mario Carneiro, 4-Sep-2016.) |
⊢ ((¬ 𝜑 ⊻ ¬ 𝜓) ↔ (𝜑 ⊻ 𝜓)) | ||
Theorem | xorbi12i 1520 | Equality property for exclusive disjunction. (Contributed by Mario Carneiro, 4-Sep-2016.) (Proof shortened by Wolf Lammen, 21-Apr-2024.) |
⊢ (𝜑 ↔ 𝜓) & ⊢ (𝜒 ↔ 𝜃) ⇒ ⊢ ((𝜑 ⊻ 𝜒) ↔ (𝜓 ⊻ 𝜃)) | ||
Theorem | xorbi12iOLD 1521 | Obsolete version of xorbi12i 1520 as of 21-Apr-2024. (Contributed by Mario Carneiro, 4-Sep-2016.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ (𝜑 ↔ 𝜓) & ⊢ (𝜒 ↔ 𝜃) ⇒ ⊢ ((𝜑 ⊻ 𝜒) ↔ (𝜓 ⊻ 𝜃)) | ||
Theorem | xorbi12d 1522 | Equality property for exclusive disjunction. (Contributed by Mario Carneiro, 4-Sep-2016.) |
⊢ (𝜑 → (𝜓 ↔ 𝜒)) & ⊢ (𝜑 → (𝜃 ↔ 𝜏)) ⇒ ⊢ (𝜑 → ((𝜓 ⊻ 𝜃) ↔ (𝜒 ⊻ 𝜏))) | ||
Theorem | anxordi 1523 | Conjunction distributes over exclusive-or. In intuitionistic logic this assertion is also true, even though xordi 1014 does not necessarily hold, in part because the usual definition of xor is subtly different in intuitionistic logic. (Contributed by David A. Wheeler, 7-Oct-2018.) |
⊢ ((𝜑 ∧ (𝜓 ⊻ 𝜒)) ↔ ((𝜑 ∧ 𝜓) ⊻ (𝜑 ∧ 𝜒))) | ||
Theorem | xorexmid 1524 | Exclusive-or variant of the law of the excluded middle (exmid 892). This statement is ancient, going back to at least Stoic logic. This statement does not necessarily hold in intuitionistic logic. (Contributed by David A. Wheeler, 23-Feb-2019.) |
⊢ (𝜑 ⊻ ¬ 𝜑) | ||
Syntax | wnor 1525 | Extend wff definition to include joint denial ("nor"). |
wff (𝜑 ⊽ 𝜓) | ||
Definition | df-nor 1526 | Define joint denial ("not-or" or "nor"). After we define the constant true ⊤ (df-tru 1542) and the constant false ⊥ (df-fal 1552), we will be able to prove these truth table values: ((⊤ ⊽ ⊤) ↔ ⊥) (trunortru 1588), ((⊤ ⊽ ⊥) ↔ ⊥) (trunorfal 1589), ((⊥ ⊽ ⊤) ↔ ⊥) (falnortru 1591), and ((⊥ ⊽ ⊥) ↔ ⊤) (falnorfal 1592). Contrast with ∧ (df-an 397), ∨ (df-or 845), → (wi 4), ⊼ (df-nan 1487), and ⊻ (df-xor 1507). (Contributed by Remi, 25-Oct-2023.) |
⊢ ((𝜑 ⊽ 𝜓) ↔ ¬ (𝜑 ∨ 𝜓)) | ||
Theorem | norcom 1527 | The connector ⊽ is commutative. (Contributed by Remi, 25-Oct-2023.) (Proof shortened by Wolf Lammen, 23-Apr-2024.) |
⊢ ((𝜑 ⊽ 𝜓) ↔ (𝜓 ⊽ 𝜑)) | ||
Theorem | norcomOLD 1528 | Obsolete version of norcom 1527 as of 23-Apr-2024. (Contributed by Remi, 25-Oct-2023.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ ((𝜑 ⊽ 𝜓) ↔ (𝜓 ⊽ 𝜑)) | ||
Theorem | nornot 1529 | ¬ is expressible via ⊽. (Contributed by Remi, 25-Oct-2023.) (Proof shortened by Wolf Lammen, 8-Dec-2023.) |
⊢ (¬ 𝜑 ↔ (𝜑 ⊽ 𝜑)) | ||
Theorem | noran 1530 | ∧ is expressible via ⊽. (Contributed by Remi, 26-Oct-2023.) (Proof shortened by Wolf Lammen, 8-Dec-2023.) |
⊢ ((𝜑 ∧ 𝜓) ↔ ((𝜑 ⊽ 𝜑) ⊽ (𝜓 ⊽ 𝜓))) | ||
Theorem | noror 1531 | ∨ is expressible via ⊽. (Contributed by Remi, 26-Oct-2023.) (Proof shortened by Wolf Lammen, 8-Dec-2023.) |
⊢ ((𝜑 ∨ 𝜓) ↔ ((𝜑 ⊽ 𝜓) ⊽ (𝜑 ⊽ 𝜓))) | ||
Theorem | norasslem1 1532 | This lemma shows the equivalence of two expressions, used in norass 1535. (Contributed by Wolf Lammen, 18-Dec-2023.) |
⊢ (((𝜑 ∨ 𝜓) → 𝜒) ↔ ((𝜑 ⊽ 𝜓) ∨ 𝜒)) | ||
Theorem | norasslem2 1533 | This lemma specializes biimt 361 suitably for the proof of norass 1535. (Contributed by Wolf Lammen, 18-Dec-2023.) |
⊢ (𝜑 → (𝜓 ↔ ((𝜑 ∨ 𝜒) → 𝜓))) | ||
Theorem | norasslem3 1534 | This lemma specializes biorf 934 suitably for the proof of norass 1535. (Contributed by Wolf Lammen, 18-Dec-2023.) |
⊢ (¬ 𝜑 → ((𝜓 → 𝜒) ↔ ((𝜑 ∨ 𝜓) → 𝜒))) | ||
Theorem | norass 1535 | A characterization of when an expression involving joint denials associates. This is identical to the case when alternative denial is associative, see nanass 1505. Remark: Like alternative denial, joint denial is also commutative, see norcom 1527. (Contributed by RP, 29-Oct-2023.) (Proof shortened by Wolf Lammen, 17-Dec-2023.) |
⊢ ((𝜑 ↔ 𝜒) ↔ (((𝜑 ⊽ 𝜓) ⊽ 𝜒) ↔ (𝜑 ⊽ (𝜓 ⊽ 𝜒)))) | ||
Theorem | norassOLD 1536 | Obsolete version of norass 1535 as of 17-Dec-2023. (Contributed by RP, 29-Oct-2023.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ ((𝜑 ↔ 𝜒) ↔ (((𝜑 ⊽ 𝜓) ⊽ 𝜒) ↔ (𝜑 ⊽ (𝜓 ⊽ 𝜒)))) | ||
Even though it is not ordinarily part of propositional calculus, the universal quantifier ∀ is introduced here so that the soundness of Definition df-tru 1542 can be checked by the same algorithm that is used for predicate calculus. Its first real use is in Definition df-ex 1783 in the predicate calculus section below. For those who want propositional calculus to be self-contained, i.e., to use wff variables only, the alternate Definition dftru2 1544 may be adopted and this subsection moved down to the start of the subsection with wex 1782 below. However, the use of dftru2 1544 as a definition requires a more elaborate definition checking algorithm that we prefer to avoid. | ||
Syntax | wal 1537 | Extend wff definition to include the universal quantifier ("for all"). ∀𝑥𝜑 is read "𝜑 (phi) is true for all 𝑥". Typically, in its final application 𝜑 would be replaced with a wff containing a (free) occurrence of the variable 𝑥, for example 𝑥 = 𝑦. In a universe with a finite number of objects, "for all" is equivalent to a big conjunction (AND) with one wff for each possible case of 𝑥. When the universe is infinite (as with set theory), such a propositional-calculus equivalent is not possible because an infinitely long formula has no meaning, but conceptually the idea is the same. |
wff ∀𝑥𝜑 | ||
Even though it is not ordinarily part of propositional calculus, the equality predicate = is introduced here so that the soundness of definition df-tru 1542 can be checked by the same algorithm as is used for predicate calculus. Its first real use is in Theorem weq 1967 in the predicate calculus section below. For those who want propositional calculus to be self-contained, i.e., to use wff variables only, the alternate definition dftru2 1544 may be adopted and this subsection moved down to just above weq 1967 below. However, the use of dftru2 1544 as a definition requires a more elaborate definition checking algorithm that we prefer to avoid. | ||
Syntax | cv 1538 |
This syntax construction states that a variable 𝑥, which has been
declared to be a setvar variable by $f statement vx, is also a class
expression. This can be justified informally as follows. We know that
the class builder {𝑦 ∣ 𝑦 ∈ 𝑥} is a class by cab 2716.
Since (when
𝑦 is distinct from 𝑥) we
have 𝑥 =
{𝑦 ∣ 𝑦 ∈ 𝑥} by
cvjust 2733, we can argue that the syntax "class 𝑥 " can be viewed as
an abbreviation for "class {𝑦 ∣ 𝑦 ∈ 𝑥}". See the discussion
under the definition of class in [Jech] p.
4 showing that "Every set can
be considered to be a class".
While it is tempting and perhaps occasionally useful to view cv 1538 as a "type conversion" from a setvar variable to a class variable, keep in mind that cv 1538 is intrinsically no different from any other class-building syntax such as cab 2716, cun 3886, or c0 4257. For a general discussion of the theory of classes and the role of cv 1538, see mmset.html#class 1538. (The description above applies to set theory, not predicate calculus. The purpose of introducing class 𝑥 here, and not in set theory where it belongs, is to allow us to express, i.e., "prove", the weq 1967 of predicate calculus from the wceq 1539 of set theory, so that we do not overload the = connective with two syntax definitions. This is done to prevent ambiguity that would complicate some Metamath parsers.) |
class 𝑥 | ||
Syntax | wceq 1539 |
Extend wff definition to include class equality.
For a general discussion of the theory of classes, see mmset.html#class. (The purpose of introducing wff 𝐴 = 𝐵 here, and not in set theory where it belongs, is to allow us to express, i.e., "prove", the weq 1967 of predicate calculus in terms of the wceq 1539 of set theory, so that we do not "overload" the = connective with two syntax definitions. This is done to prevent ambiguity that would complicate some Metamath parsers. For example, some parsers - although not the Metamath program - stumble on the fact that the = in 𝑥 = 𝑦 could be the = of either weq 1967 or wceq 1539, although mathematically it makes no difference. The class variables 𝐴 and 𝐵 are introduced temporarily for the purpose of this definition but otherwise not used in predicate calculus. See df-cleq 2731 for more information on the set theory usage of wceq 1539.) |
wff 𝐴 = 𝐵 | ||
Syntax | wtru 1540 | The constant ⊤ is a wff. |
wff ⊤ | ||
Theorem | trujust 1541 | Soundness justification theorem for df-tru 1542. Instance of monothetic 265. (Contributed by Mario Carneiro, 17-Nov-2013.) (Revised by NM, 11-Jul-2019.) |
⊢ ((∀𝑥 𝑥 = 𝑥 → ∀𝑥 𝑥 = 𝑥) ↔ (∀𝑦 𝑦 = 𝑦 → ∀𝑦 𝑦 = 𝑦)) | ||
Definition | df-tru 1542 | Definition of the truth value "true", or "verum", denoted by ⊤. In this definition, an instance of id 22 is used as the definiens, although any tautology, such as an axiom, can be used in its place. This particular instance of id 22 was chosen so this definition can be checked by the same algorithm that is used for predicate calculus. This definition should be referenced directly only by tru 1543, and other proofs should use tru 1543 instead of this definition, since there are many alternate ways to define ⊤. (Contributed by Anthony Hart, 13-Oct-2010.) (Revised by NM, 11-Jul-2019.) Use tru 1543 instead. (New usage is discouraged.) |
⊢ (⊤ ↔ (∀𝑥 𝑥 = 𝑥 → ∀𝑥 𝑥 = 𝑥)) | ||
Theorem | tru 1543 | The truth value ⊤ is provable. (Contributed by Anthony Hart, 13-Oct-2010.) |
⊢ ⊤ | ||
Theorem | dftru2 1544 | An alternate definition of "true" (see comment of df-tru 1542). The associated justification theorem is monothetic 265. (Contributed by Anthony Hart, 13-Oct-2010.) (Revised by BJ, 12-Jul-2019.) Use tru 1543 instead. (New usage is discouraged.) |
⊢ (⊤ ↔ (𝜑 → 𝜑)) | ||
Theorem | trut 1545 | A proposition is equivalent to it being implied by ⊤. Closed form of mptru 1546. Dual of dfnot 1558. It is to tbtru 1547 what a1bi 363 is to tbt 370. (Contributed by BJ, 26-Oct-2019.) |
⊢ (𝜑 ↔ (⊤ → 𝜑)) | ||
Theorem | mptru 1546 | Eliminate ⊤ as an antecedent. A proposition implied by ⊤ is true. This is modus ponens ax-mp 5 when the minor hypothesis is ⊤ (which holds by tru 1543). (Contributed by Mario Carneiro, 13-Mar-2014.) |
⊢ (⊤ → 𝜑) ⇒ ⊢ 𝜑 | ||
Theorem | tbtru 1547 | A proposition is equivalent to itself being equivalent to ⊤. (Contributed by Anthony Hart, 14-Aug-2011.) |
⊢ (𝜑 ↔ (𝜑 ↔ ⊤)) | ||
Theorem | bitru 1548 | A theorem is equivalent to truth. (Contributed by Mario Carneiro, 9-May-2015.) |
⊢ 𝜑 ⇒ ⊢ (𝜑 ↔ ⊤) | ||
Theorem | trud 1549 | Anything implies ⊤. Dual statement of falim 1556. Deduction form of tru 1543. Note on naming: in 2022, the theorem now known as mptru 1546 was renamed from trud so if you are reading documentation written before that time, references to trud refer to what is now mptru 1546. (Contributed by FL, 20-Mar-2011.) (Proof shortened by Anthony Hart, 1-Aug-2011.) |
⊢ (𝜑 → ⊤) | ||
Theorem | truan 1550 | True can be removed from a conjunction. (Contributed by FL, 20-Mar-2011.) (Proof shortened by Wolf Lammen, 21-Jul-2019.) |
⊢ ((⊤ ∧ 𝜑) ↔ 𝜑) | ||
Syntax | wfal 1551 | The constant ⊥ is a wff. |
wff ⊥ | ||
Definition | df-fal 1552 | Definition of the truth value "false", or "falsum", denoted by ⊥. See also df-tru 1542. (Contributed by Anthony Hart, 22-Oct-2010.) |
⊢ (⊥ ↔ ¬ ⊤) | ||
Theorem | fal 1553 | The truth value ⊥ is refutable. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Mel L. O'Cat, 11-Mar-2012.) |
⊢ ¬ ⊥ | ||
Theorem | nbfal 1554 | The negation of a proposition is equivalent to itself being equivalent to ⊥. (Contributed by Anthony Hart, 14-Aug-2011.) |
⊢ (¬ 𝜑 ↔ (𝜑 ↔ ⊥)) | ||
Theorem | bifal 1555 | A contradiction is equivalent to falsehood. (Contributed by Mario Carneiro, 9-May-2015.) |
⊢ ¬ 𝜑 ⇒ ⊢ (𝜑 ↔ ⊥) | ||
Theorem | falim 1556 | The truth value ⊥ implies anything. Also called the "principle of explosion", or "ex falso [sequitur]] quodlibet" (Latin for "from falsehood, anything [follows]]"). Dual statement of trud 1549. (Contributed by FL, 20-Mar-2011.) (Proof shortened by Anthony Hart, 1-Aug-2011.) |
⊢ (⊥ → 𝜑) | ||
Theorem | falimd 1557 | The truth value ⊥ implies anything. (Contributed by Mario Carneiro, 9-Feb-2017.) |
⊢ ((𝜑 ∧ ⊥) → 𝜓) | ||
Theorem | dfnot 1558 | Given falsum ⊥, we can define the negation of a wff 𝜑 as the statement that ⊥ follows from assuming 𝜑. (Contributed by Mario Carneiro, 9-Feb-2017.) (Proof shortened by Wolf Lammen, 21-Jul-2019.) |
⊢ (¬ 𝜑 ↔ (𝜑 → ⊥)) | ||
Theorem | inegd 1559 | Negation introduction rule from natural deduction. (Contributed by Mario Carneiro, 9-Feb-2017.) |
⊢ ((𝜑 ∧ 𝜓) → ⊥) ⇒ ⊢ (𝜑 → ¬ 𝜓) | ||
Theorem | efald 1560 | Deduction based on reductio ad absurdum. (Contributed by Mario Carneiro, 9-Feb-2017.) |
⊢ ((𝜑 ∧ ¬ 𝜓) → ⊥) ⇒ ⊢ (𝜑 → 𝜓) | ||
Theorem | pm2.21fal 1561 | If a wff and its negation are provable, then falsum is provable. (Contributed by Mario Carneiro, 9-Feb-2017.) |
⊢ (𝜑 → 𝜓) & ⊢ (𝜑 → ¬ 𝜓) ⇒ ⊢ (𝜑 → ⊥) | ||
Some sources define logical connectives by their truth tables. These are tables that give the truth value of the composed expression for all possible combinations of the truth values of their arguments. In this section, we show that our definitions and axioms produce equivalent results for all the logical connectives we have introduced (either axiomatically or by a definition): implication wi 4, negation wn 3, biconditional df-bi 206, conjunction df-an 397, disjunction df-or 845, alternative denial df-nan 1487, exclusive disjunction df-xor 1507. | ||
Theorem | truimtru 1562 | A → identity. (Contributed by Anthony Hart, 22-Oct-2010.) An alternate proof is possible using trud 1549 instead of id 22 but the principle of identity id 22 is more basic, and the present proof indicates that the result still holds in relevance logic. (Proof modification is discouraged.) |
⊢ ((⊤ → ⊤) ↔ ⊤) | ||
Theorem | truimfal 1563 | A → identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) |
⊢ ((⊤ → ⊥) ↔ ⊥) | ||
Theorem | falimtru 1564 | A → identity. (Contributed by Anthony Hart, 22-Oct-2010.) An alternate proof is possible using falim 1556 instead of trud 1549 but the present proof using trud 1549 emphasizes that the result does not require the principle of explosion. (Proof modification is discouraged.) |
⊢ ((⊥ → ⊤) ↔ ⊤) | ||
Theorem | falimfal 1565 | A → identity. (Contributed by Anthony Hart, 22-Oct-2010.) An alternate proof is possible using falim 1556 instead of id 22 but the present proof using id 22 emphasizes that the result does not require the principle of explosion. (Proof modification is discouraged.) |
⊢ ((⊥ → ⊥) ↔ ⊤) | ||
Theorem | nottru 1566 | A ¬ identity. (Contributed by Anthony Hart, 22-Oct-2010.) |
⊢ (¬ ⊤ ↔ ⊥) | ||
Theorem | notfal 1567 | A ¬ identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) |
⊢ (¬ ⊥ ↔ ⊤) | ||
Theorem | trubitru 1568 | A ↔ identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) |
⊢ ((⊤ ↔ ⊤) ↔ ⊤) | ||
Theorem | falbitru 1569 | A ↔ identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) (Proof shortened by Wolf Lammen, 10-Jul-2020.) |
⊢ ((⊥ ↔ ⊤) ↔ ⊥) | ||
Theorem | trubifal 1570 | A ↔ identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) (Proof shortened by Wolf Lammen, 10-Jul-2020.) |
⊢ ((⊤ ↔ ⊥) ↔ ⊥) | ||
Theorem | falbifal 1571 | A ↔ identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) |
⊢ ((⊥ ↔ ⊥) ↔ ⊤) | ||
Theorem | truantru 1572 | A ∧ identity. (Contributed by Anthony Hart, 22-Oct-2010.) |
⊢ ((⊤ ∧ ⊤) ↔ ⊤) | ||
Theorem | truanfal 1573 | A ∧ identity. (Contributed by Anthony Hart, 22-Oct-2010.) |
⊢ ((⊤ ∧ ⊥) ↔ ⊥) | ||
Theorem | falantru 1574 | A ∧ identity. (Contributed by Anthony Hart, 22-Oct-2010.) |
⊢ ((⊥ ∧ ⊤) ↔ ⊥) | ||
Theorem | falanfal 1575 | A ∧ identity. (Contributed by Anthony Hart, 22-Oct-2010.) |
⊢ ((⊥ ∧ ⊥) ↔ ⊥) | ||
Theorem | truortru 1576 | A ∨ identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) |
⊢ ((⊤ ∨ ⊤) ↔ ⊤) | ||
Theorem | truorfal 1577 | A ∨ identity. (Contributed by Anthony Hart, 22-Oct-2010.) |
⊢ ((⊤ ∨ ⊥) ↔ ⊤) | ||
Theorem | falortru 1578 | A ∨ identity. (Contributed by Anthony Hart, 22-Oct-2010.) |
⊢ ((⊥ ∨ ⊤) ↔ ⊤) | ||
Theorem | falorfal 1579 | A ∨ identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) |
⊢ ((⊥ ∨ ⊥) ↔ ⊥) | ||
Theorem | trunantru 1580 | A ⊼ identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) |
⊢ ((⊤ ⊼ ⊤) ↔ ⊥) | ||
Theorem | trunanfal 1581 | A ⊼ identity. (Contributed by Anthony Hart, 23-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) (Proof shortened by Wolf Lammen, 10-Jul-2020.) |
⊢ ((⊤ ⊼ ⊥) ↔ ⊤) | ||
Theorem | falnantru 1582 | A ⊼ identity. (Contributed by Anthony Hart, 23-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) |
⊢ ((⊥ ⊼ ⊤) ↔ ⊤) | ||
Theorem | falnanfal 1583 | A ⊼ identity. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Andrew Salmon, 13-May-2011.) |
⊢ ((⊥ ⊼ ⊥) ↔ ⊤) | ||
Theorem | truxortru 1584 | A ⊻ identity. (Contributed by David A. Wheeler, 8-May-2015.) |
⊢ ((⊤ ⊻ ⊤) ↔ ⊥) | ||
Theorem | truxorfal 1585 | A ⊻ identity. (Contributed by David A. Wheeler, 8-May-2015.) |
⊢ ((⊤ ⊻ ⊥) ↔ ⊤) | ||
Theorem | falxortru 1586 | A ⊻ identity. (Contributed by David A. Wheeler, 9-May-2015.) (Proof shortened by Wolf Lammen, 10-Jul-2020.) |
⊢ ((⊥ ⊻ ⊤) ↔ ⊤) | ||
Theorem | falxorfal 1587 | A ⊻ identity. (Contributed by David A. Wheeler, 9-May-2015.) |
⊢ ((⊥ ⊻ ⊥) ↔ ⊥) | ||
Theorem | trunortru 1588 | A ⊽ identity. (Contributed by Remi, 25-Oct-2023.) (Proof shortened by Wolf Lammen, 7-Dec-2023.) |
⊢ ((⊤ ⊽ ⊤) ↔ ⊥) | ||
Theorem | trunorfal 1589 | A ⊽ identity. (Contributed by Remi, 25-Oct-2023.) (Proof shortened by Wolf Lammen, 17-Dec-2023.) |
⊢ ((⊤ ⊽ ⊥) ↔ ⊥) | ||
Theorem | trunorfalOLD 1590 | Obsolete version of trunorfal 1589 as of 17-Dec-2023. (Contributed by Remi, 25-Oct-2023.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ ((⊤ ⊽ ⊥) ↔ ⊥) | ||
Theorem | falnortru 1591 | A ⊽ identity. (Contributed by Remi, 25-Oct-2023.) |
⊢ ((⊥ ⊽ ⊤) ↔ ⊥) | ||
Theorem | falnorfal 1592 | A ⊽ identity. (Contributed by Remi, 25-Oct-2023.) (Proof shortened by Wolf Lammen, 17-Dec-2023.) |
⊢ ((⊥ ⊽ ⊥) ↔ ⊤) | ||
Theorem | falnorfalOLD 1593 | Obsolete version of falnorfal 1592 as of 17-Dec-2023. (Contributed by Remi, 25-Oct-2023.) (Proof modification is discouraged.) (New usage is discouraged.) |
⊢ ((⊥ ⊽ ⊥) ↔ ⊤) | ||
Propositional calculus deals with truth values, which can be interpreted as bits. Using this, we can define the half adder and the full adder in pure propositional calculus, and show their basic properties. The half adder adds two 1-bit numbers. Its two outputs are the "sum" S and the "carry" C. The real sum is then given by 2C+S. The sum and carry correspond respectively to the logical exclusive disjunction (df-xor 1507) and the logical conjunction (df-an 397). The full adder takes into account an "input carry", so it has three inputs and again two outputs, corresponding to the "sum" (df-had 1595) and "updated carry" (df-cad 1609). Here is a short description. We code the bit 0 by ⊥ and 1 by ⊤. Even though hadd and cadd are invariant under permutation of their arguments, assume for the sake of concreteness that 𝜑 (resp. 𝜓) is the i^th bit of the first (resp. second) number to add (with the convention that the i^th bit is the multiple of 2^i in the base-2 representation), and that 𝜒 is the i^th carry (with the convention that the 0^th carry is 0). Then, hadd(𝜑, 𝜓, 𝜒) gives the i^th bit of the sum, and cadd(𝜑, 𝜓, 𝜒) gives the (i+1)^th carry. Then, addition is performed by iteration from i = 0 to i = 1 + (max of the number of digits of the two summands) by "updating" the carry. | ||
Syntax | whad 1594 | Syntax for the "sum" output of the full adder. (Contributed by Mario Carneiro, 4-Sep-2016.) |
wff hadd(𝜑, 𝜓, 𝜒) | ||
Definition | df-had 1595 | Definition of the "sum" output of the full adder (triple exclusive disjunction, or XOR3, or testing whether an odd number of parameters are true). (Contributed by Mario Carneiro, 4-Sep-2016.) |
⊢ (hadd(𝜑, 𝜓, 𝜒) ↔ ((𝜑 ⊻ 𝜓) ⊻ 𝜒)) | ||
Theorem | hadbi123d 1596 | Equality theorem for the adder sum. (Contributed by Mario Carneiro, 4-Sep-2016.) |
⊢ (𝜑 → (𝜓 ↔ 𝜒)) & ⊢ (𝜑 → (𝜃 ↔ 𝜏)) & ⊢ (𝜑 → (𝜂 ↔ 𝜁)) ⇒ ⊢ (𝜑 → (hadd(𝜓, 𝜃, 𝜂) ↔ hadd(𝜒, 𝜏, 𝜁))) | ||
Theorem | hadbi123i 1597 | Equality theorem for the adder sum. (Contributed by Mario Carneiro, 4-Sep-2016.) |
⊢ (𝜑 ↔ 𝜓) & ⊢ (𝜒 ↔ 𝜃) & ⊢ (𝜏 ↔ 𝜂) ⇒ ⊢ (hadd(𝜑, 𝜒, 𝜏) ↔ hadd(𝜓, 𝜃, 𝜂)) | ||
Theorem | hadass 1598 | Associative law for the adder sum. (Contributed by Mario Carneiro, 4-Sep-2016.) |
⊢ (hadd(𝜑, 𝜓, 𝜒) ↔ (𝜑 ⊻ (𝜓 ⊻ 𝜒))) | ||
Theorem | hadbi 1599 | The adder sum is the same as the triple biconditional. (Contributed by Mario Carneiro, 4-Sep-2016.) |
⊢ (hadd(𝜑, 𝜓, 𝜒) ↔ ((𝜑 ↔ 𝜓) ↔ 𝜒)) | ||
Theorem | hadcoma 1600 | Commutative law for the adder sum. (Contributed by Mario Carneiro, 4-Sep-2016.) (Proof shortened by Wolf Lammen, 17-Dec-2023.) |
⊢ (hadd(𝜑, 𝜓, 𝜒) ↔ hadd(𝜓, 𝜑, 𝜒)) |
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