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Most recent proofs    These are the 100 (Unicode, GIF) or 1000 (Unicode, GIF) most recent proofs in the iset.mm database for the Intuitionistic Logic Explorer. The iset.mm database is maintained on GitHub with master (stable) and develop (development) versions. This page was created from the commit given on the MPE Most Recent Proofs page. The database from that commit is also available here: iset.mm.

See the MPE Most Recent Proofs page for news and some useful links.

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Last updated on 18-Feb-2026 at 7:16 AM ET.
Recent Additions to the Intuitionistic Logic Explorer
DateLabelDescription
Theorem
 
14-Feb-2026pw1ninf 16384 The powerset of 1o is not infinite. Since we cannot prove it is finite (see pw1fin 7080), this provides a concrete example of a set which we cannot show to be finite or infinite, as seen another way at inffiexmid 7076. (Contributed by Jim Kingdon, 14-Feb-2026.)
¬ ω ≼ 𝒫 1o
 
14-Feb-2026pw1ndom3 16383 The powerset of 1o does not dominate 3o. This is another way of saying that 𝒫 1o does not have three elements (like pwntru 4283). (Contributed by Steven Nguyen and Jim Kingdon, 14-Feb-2026.)
¬ 3o ≼ 𝒫 1o
 
14-Feb-2026pw1ndom3lem 16382 Lemma for pw1ndom3 16383. (Contributed by Jim Kingdon, 14-Feb-2026.)
(𝜑𝑋 ∈ 𝒫 1o)    &   (𝜑𝑌 ∈ 𝒫 1o)    &   (𝜑𝑍 ∈ 𝒫 1o)    &   (𝜑𝑋𝑌)    &   (𝜑𝑋𝑍)    &   (𝜑𝑌𝑍)       (𝜑𝑋 = ∅)
 
12-Feb-2026pw1dceq 16399 The powerset of 1o having decidable equality is equivalent to excluded middle. (Contributed by Jim Kingdon, 12-Feb-2026.)
(EXMID ↔ ∀𝑥 ∈ 𝒫 1o𝑦 ∈ 𝒫 1oDECID 𝑥 = 𝑦)
 
12-Feb-20263dom 16381 A set that dominates ordinal 3 has at least 3 different members. (Contributed by Jim Kingdon, 12-Feb-2026.)
(3o𝐴 → ∃𝑥𝐴𝑦𝐴𝑧𝐴 (𝑥𝑦𝑥𝑧𝑦𝑧))
 
10-Feb-2026fidcen 16379 Equinumerosity of finite sets is decidable. (Contributed by Jim Kingdon, 10-Feb-2026.)
((𝐴 ∈ Fin ∧ 𝐵 ∈ Fin) → DECID 𝐴𝐵)
 
8-Feb-2026wlkvtxm 16061 A graph with a walk has at least one vertex. (Contributed by Jim Kingdon, 8-Feb-2026.)
𝑉 = (Vtx‘𝐺)       (𝐹(Walks‘𝐺)𝑃 → ∃𝑥 𝑥𝑉)
 
7-Feb-2026trlsv 16103 The classes involved in a trail are sets. (Contributed by Jim Kingdon, 7-Feb-2026.)
(𝐹(Trails‘𝐺)𝑃 → (𝐺 ∈ V ∧ 𝐹 ∈ V ∧ 𝑃 ∈ V))
 
7-Feb-2026wlkex 16046 The class of walks on a graph is a set. (Contributed by Jim Kingdon, 7-Feb-2026.)
(𝐺𝑉 → (Walks‘𝐺) ∈ V)
 
3-Feb-2026dom1oi 6986 A set with an element dominates one. (Contributed by Jim Kingdon, 3-Feb-2026.)
((𝐴𝑉𝐵𝐴) → 1o𝐴)
 
2-Feb-2026edginwlkd 16076 The value of the edge function for an index of an edge within a walk is an edge. (Contributed by AV, 2-Jan-2021.) (Revised by AV, 9-Dec-2021.) (Revised by Jim Kingdon, 2-Feb-2026.)
𝐼 = (iEdg‘𝐺)    &   𝐸 = (Edg‘𝐺)    &   (𝜑 → Fun 𝐼)    &   (𝜑𝐹 ∈ Word dom 𝐼)    &   (𝜑𝐾 ∈ (0..^(♯‘𝐹)))    &   (𝜑𝐺𝑉)       (𝜑 → (𝐼‘(𝐹𝐾)) ∈ 𝐸)
 
2-Feb-2026wlkelvv 16070 A walk is an ordered pair. (Contributed by Jim Kingdon, 2-Feb-2026.)
(𝑊 ∈ (Walks‘𝐺) → 𝑊 ∈ (V × V))
 
1-Feb-2026wlkcprim 16071 A walk as class with two components. (Contributed by Alexander van der Vekens, 22-Jul-2018.) (Revised by AV, 2-Jan-2021.) (Revised by Jim Kingdon, 1-Feb-2026.)
(𝑊 ∈ (Walks‘𝐺) → (1st𝑊)(Walks‘𝐺)(2nd𝑊))
 
1-Feb-2026wlkmex 16040 If there are walks on a graph, the graph is a set. (Contributed by Jim Kingdon, 1-Feb-2026.)
(𝑊 ∈ (Walks‘𝐺) → 𝐺 ∈ V)
 
31-Jan-2026fvmbr 5664 If a function value is inhabited, the argument is related to the function value. (Contributed by Jim Kingdon, 31-Jan-2026.)
(𝐴 ∈ (𝐹𝑋) → 𝑋𝐹(𝐹𝑋))
 
30-Jan-2026elfvex 5663 If a function value is inhabited, the function value is a set. (Contributed by Jim Kingdon, 30-Jan-2026.)
(𝐴 ∈ (𝐹𝐵) → (𝐹𝐵) ∈ V)
 
30-Jan-2026reldmm 4942 A relation is inhabited iff its domain is inhabited. (Contributed by Jim Kingdon, 30-Jan-2026.)
(Rel 𝐴 → (∃𝑥 𝑥𝐴 ↔ ∃𝑦 𝑦 ∈ dom 𝐴))
 
25-Jan-2026ifp2 986 Forward direction of dfifp2dc 987. This direction does not require decidability. (Contributed by Jim Kingdon, 25-Jan-2026.)
(if-(𝜑, 𝜓, 𝜒) → ((𝜑𝜓) ∧ (¬ 𝜑𝜒)))
 
25-Jan-2026ifpdc 985 The conditional operator for propositions implies decidability. (Contributed by Jim Kingdon, 25-Jan-2026.)
(if-(𝜑, 𝜓, 𝜒) → DECID 𝜑)
 
20-Jan-2026cats1fvd 11306 A symbol other than the last in a concatenation with a singleton word. (Contributed by Mario Carneiro, 26-Feb-2016.) (Revised by Jim Kingdon, 20-Jan-2026.)
𝑇 = (𝑆 ++ ⟨“𝑋”⟩)    &   (𝜑𝑆 ∈ Word V)    &   (𝜑 → (♯‘𝑆) = 𝑀)    &   (𝜑𝑌𝑉)    &   (𝜑𝑋𝑊)    &   (𝜑 → (𝑆𝑁) = 𝑌)    &   (𝜑𝑁 ∈ ℕ0)    &   (𝜑𝑁 < 𝑀)       (𝜑 → (𝑇𝑁) = 𝑌)
 
20-Jan-2026cats1fvnd 11305 The last symbol of a concatenation with a singleton word. (Contributed by Mario Carneiro, 26-Feb-2016.) (Revised by Jim Kingdon, 20-Jan-2026.)
𝑇 = (𝑆 ++ ⟨“𝑋”⟩)    &   (𝜑𝑆 ∈ Word V)    &   (𝜑𝑋𝑉)    &   (𝜑 → (♯‘𝑆) = 𝑀)       (𝜑 → (𝑇𝑀) = 𝑋)
 
19-Jan-2026cats2catd 11309 Closure of concatenation of concatenations with singleton words. (Contributed by AV, 1-Mar-2021.) (Revised by Jim Kingdon, 19-Jan-2026.)
(𝜑𝐵 ∈ Word V)    &   (𝜑𝐷 ∈ Word V)    &   (𝜑𝑋𝑉)    &   (𝜑𝑌𝑊)    &   (𝜑𝐴 = (𝐵 ++ ⟨“𝑋”⟩))    &   (𝜑𝐶 = (⟨“𝑌”⟩ ++ 𝐷))       (𝜑 → (𝐴 ++ 𝐶) = ((𝐵 ++ ⟨“𝑋𝑌”⟩) ++ 𝐷))
 
19-Jan-2026cats1catd 11308 Closure of concatenation with a singleton word. (Contributed by Mario Carneiro, 26-Feb-2016.) (Revised by Jim Kingdon, 19-Jan-2026.)
𝑇 = (𝑆 ++ ⟨“𝑋”⟩)    &   (𝜑𝐴 ∈ Word V)    &   (𝜑𝑆 ∈ Word V)    &   (𝜑𝑋𝑊)    &   (𝜑𝐶 = (𝐵 ++ ⟨“𝑋”⟩))    &   (𝜑𝐵 = (𝐴 ++ 𝑆))       (𝜑𝐶 = (𝐴 ++ 𝑇))
 
19-Jan-2026cats1lend 11307 The length of concatenation with a singleton word. (Contributed by Mario Carneiro, 26-Feb-2016.) (Revised by Jim Kingdon, 19-Jan-2026.)
𝑇 = (𝑆 ++ ⟨“𝑋”⟩)    &   (𝜑𝑆 ∈ Word V)    &   (𝜑𝑋𝑊)    &   (♯‘𝑆) = 𝑀    &   (𝑀 + 1) = 𝑁       (𝜑 → (♯‘𝑇) = 𝑁)
 
18-Jan-2026rexanaliim 2636 A transformation of restricted quantifiers and logical connectives. (Contributed by NM, 4-Sep-2005.) (Revised by Jim Kingdon, 18-Jan-2026.)
(∃𝑥𝐴 (𝜑 ∧ ¬ 𝜓) → ¬ ∀𝑥𝐴 (𝜑𝜓))
 
15-Jan-2026df-uspgren 15961 Define the class of all undirected simple pseudographs (which could have loops). An undirected simple pseudograph is a special undirected pseudograph or a special undirected simple hypergraph, consisting of a set 𝑣 (of "vertices") and an injective (one-to-one) function 𝑒 (representing (indexed) "edges") into subsets of 𝑣 of cardinality one or two, representing the two vertices incident to the edge, or the one vertex if the edge is a loop. In contrast to a pseudograph, there is at most one edge between two vertices resp. at most one loop for a vertex. (Contributed by Alexander van der Vekens, 10-Aug-2017.) (Revised by Jim Kingdon, 15-Jan-2026.)
USPGraph = {𝑔[(Vtx‘𝑔) / 𝑣][(iEdg‘𝑔) / 𝑒]𝑒:dom 𝑒1-1→{𝑥 ∈ 𝒫 𝑣 ∣ (𝑥 ≈ 1o𝑥 ≈ 2o)}}
 
11-Jan-2026en2prde 7374 A set of size two is an unordered pair of two different elements. (Contributed by Alexander van der Vekens, 8-Dec-2017.) (Revised by Jim Kingdon, 11-Jan-2026.)
(𝑉 ≈ 2o → ∃𝑎𝑏(𝑎𝑏𝑉 = {𝑎, 𝑏}))
 
10-Jan-2026pw1mapen 16391 Equinumerosity of (𝒫 1o𝑚 𝐴) and the set of subsets of 𝐴. (Contributed by Jim Kingdon, 10-Jan-2026.)
(𝐴𝑉 → (𝒫 1o𝑚 𝐴) ≈ 𝒫 𝐴)
 
10-Jan-2026pw1if 7418 Expressing a truth value in terms of an if expression. (Contributed by Jim Kingdon, 10-Jan-2026.)
(𝐴 ∈ 𝒫 1o → if(𝐴 = 1o, 1o, ∅) = 𝐴)
 
10-Jan-2026pw1m 7417 A truth value which is inhabited is equal to true. This is a variation of pwntru 4283 and pwtrufal 16392. (Contributed by Jim Kingdon, 10-Jan-2026.)
((𝐴 ∈ 𝒫 1o ∧ ∃𝑥 𝑥𝐴) → 𝐴 = 1o)
 
10-Jan-20261ndom2 7034 Two is not dominated by one. (Contributed by Jim Kingdon, 10-Jan-2026.)
¬ 2o ≼ 1o
 
9-Jan-2026pw1map 16390 Mapping between (𝒫 1o𝑚 𝐴) and subsets of 𝐴. (Contributed by Jim Kingdon, 9-Jan-2026.)
𝐹 = (𝑠 ∈ (𝒫 1o𝑚 𝐴) ↦ {𝑧𝐴 ∣ (𝑠𝑧) = 1o})       (𝐴𝑉𝐹:(𝒫 1o𝑚 𝐴)–1-1-onto→𝒫 𝐴)
 
9-Jan-2026iftrueb01 7416 Using an if expression to represent a truth value by or 1o. Unlike some theorems using if, 𝜑 does not need to be decidable. (Contributed by Jim Kingdon, 9-Jan-2026.)
(if(𝜑, 1o, ∅) = 1o𝜑)
 
8-Jan-2026pfxclz 11219 Closure of the prefix extractor. This extends pfxclg 11218 from 0 to (negative lengths are trivial, resulting in the empty word). (Contributed by Jim Kingdon, 8-Jan-2026.)
((𝑆 ∈ Word 𝐴𝐿 ∈ ℤ) → (𝑆 prefix 𝐿) ∈ Word 𝐴)
 
8-Jan-2026fnpfx 11217 The domain of the prefix extractor. (Contributed by Jim Kingdon, 8-Jan-2026.)
prefix Fn (V × ℕ0)
 
7-Jan-2026pr1or2 7375 An unordered pair, with decidable equality for the specified elements, has either one or two elements. (Contributed by Jim Kingdon, 7-Jan-2026.)
((𝐴𝐶𝐵𝐷DECID 𝐴 = 𝐵) → ({𝐴, 𝐵} ≈ 1o ∨ {𝐴, 𝐵} ≈ 2o))
 
6-Jan-2026upgr1elem1 15928 Lemma for upgr1edc 15929. (Contributed by AV, 16-Oct-2020.) (Revised by Jim Kingdon, 6-Jan-2026.)
(𝜑 → {𝐵, 𝐶} ∈ 𝑆)    &   (𝜑𝐵𝑊)    &   (𝜑𝐶𝑋)    &   (𝜑DECID 𝐵 = 𝐶)       (𝜑 → {{𝐵, 𝐶}} ⊆ {𝑥𝑆 ∣ (𝑥 ≈ 1o𝑥 ≈ 2o)})
 
3-Jan-2026df-umgren 15902 Define the class of all undirected multigraphs. An (undirected) multigraph consists of a set 𝑣 (of "vertices") and a function 𝑒 (representing indexed "edges") into subsets of 𝑣 of cardinality two, representing the two vertices incident to the edge. In contrast to a pseudograph, a multigraph has no loop. This is according to Chartrand, Gary and Zhang, Ping (2012): "A First Course in Graph Theory.", Dover, ISBN 978-0-486-48368-9, section 1.4, p. 26: "A multigraph M consists of a finite nonempty set V of vertices and a set E of edges, where every two vertices of M are joined by a finite number of edges (possibly zero). If two or more edges join the same pair of (distinct) vertices, then these edges are called parallel edges." (Contributed by AV, 24-Nov-2020.) (Revised by Jim Kingdon, 3-Jan-2026.)
UMGraph = {𝑔[(Vtx‘𝑔) / 𝑣][(iEdg‘𝑔) / 𝑒]𝑒:dom 𝑒⟶{𝑥 ∈ 𝒫 𝑣𝑥 ≈ 2o}}
 
3-Jan-2026df-upgren 15901 Define the class of all undirected pseudographs. An (undirected) pseudograph consists of a set 𝑣 (of "vertices") and a function 𝑒 (representing indexed "edges") into subsets of 𝑣 of cardinality one or two, representing the two vertices incident to the edge, or the one vertex if the edge is a loop. This is according to Chartrand, Gary and Zhang, Ping (2012): "A First Course in Graph Theory.", Dover, ISBN 978-0-486-48368-9, section 1.4, p. 26: "In a pseudograph, not only are parallel edges permitted but an edge is also permitted to join a vertex to itself. Such an edge is called a loop." (in contrast to a multigraph, see df-umgren 15902). (Contributed by Mario Carneiro, 11-Mar-2015.) (Revised by AV, 24-Nov-2020.) (Revised by Jim Kingdon, 3-Jan-2026.)
UPGraph = {𝑔[(Vtx‘𝑔) / 𝑣][(iEdg‘𝑔) / 𝑒]𝑒:dom 𝑒⟶{𝑥 ∈ 𝒫 𝑣 ∣ (𝑥 ≈ 1o𝑥 ≈ 2o)}}
 
3-Jan-2026dom1o 6985 Two ways of saying that a set is inhabited. (Contributed by Jim Kingdon, 3-Jan-2026.)
(𝐴𝑉 → (1o𝐴 ↔ ∃𝑗 𝑗𝐴))
 
3-Jan-2026en2m 6982 A set with two elements is inhabited. (Contributed by Jim Kingdon, 3-Jan-2026.)
(𝐴 ≈ 2o → ∃𝑥 𝑥𝐴)
 
3-Jan-2026en1m 6965 A set with one element is inhabited. (Contributed by Jim Kingdon, 3-Jan-2026.)
(𝐴 ≈ 1o → ∃𝑥 𝑥𝐴)
 
31-Dec-2025pw0ss 15891 There are no inhabited subsets of the empty set. (Contributed by Jim Kingdon, 31-Dec-2025.)
{𝑠 ∈ 𝒫 ∅ ∣ ∃𝑗 𝑗𝑠} = ∅
 
31-Dec-2025df-ushgrm 15878 Define the class of all undirected simple hypergraphs. An undirected simple hypergraph is a special (non-simple, multiple, multi-) hypergraph for which the edge function 𝑒 is an injective (one-to-one) function into subsets of the set of vertices 𝑣, representing the (one or more) vertices incident to the edge. This definition corresponds to the definition of hypergraphs in section I.1 of [Bollobas] p. 7 (except that the empty set seems to be allowed to be an "edge") or section 1.10 of [Diestel] p. 27, where "E is a subset of [...] the power set of V, that is the set of all subsets of V" resp. "the elements of E are nonempty subsets (of any cardinality) of V". (Contributed by AV, 19-Jan-2020.) (Revised by Jim Kingdon, 31-Dec-2025.)
USHGraph = {𝑔[(Vtx‘𝑔) / 𝑣][(iEdg‘𝑔) / 𝑒]𝑒:dom 𝑒1-1→{𝑠 ∈ 𝒫 𝑣 ∣ ∃𝑗 𝑗𝑠}}
 
29-Dec-2025df-uhgrm 15877 Define the class of all undirected hypergraphs. An undirected hypergraph consists of a set 𝑣 (of "vertices") and a function 𝑒 (representing indexed "edges") into the set of inhabited subsets of this set. (Contributed by Alexander van der Vekens, 26-Dec-2017.) (Revised by Jim Kingdon, 29-Dec-2025.)
UHGraph = {𝑔[(Vtx‘𝑔) / 𝑣][(iEdg‘𝑔) / 𝑒]𝑒:dom 𝑒⟶{𝑠 ∈ 𝒫 𝑣 ∣ ∃𝑗 𝑗𝑠}}
 
29-Dec-2025iedgex 15828 Applying the indexed edge function yields a set. (Contributed by Jim Kingdon, 29-Dec-2025.)
(𝐺𝑉 → (iEdg‘𝐺) ∈ V)
 
29-Dec-2025vtxex 15827 Applying the vertex function yields a set. (Contributed by Jim Kingdon, 29-Dec-2025.)
(𝐺𝑉 → (Vtx‘𝐺) ∈ V)
 
29-Dec-2025snmb 3788 A singleton is inhabited iff its argument is a set. (Contributed by Scott Fenton, 8-May-2018.) (Revised by Jim Kingdon, 29-Dec-2025.)
(𝐴 ∈ V ↔ ∃𝑥 𝑥 ∈ {𝐴})
 
27-Dec-2025lswex 11131 Existence of the last symbol. The last symbol of a word is a set. See lsw0g 11128 or lswcl 11130 if you want more specific results for empty or nonempty words, respectively. (Contributed by Jim Kingdon, 27-Dec-2025.)
(𝑊 ∈ Word 𝑉 → (lastS‘𝑊) ∈ V)
 
23-Dec-2025fzowrddc 11187 Decidability of whether a range of integers is a subset of a word's domain. (Contributed by Jim Kingdon, 23-Dec-2025.)
((𝑆 ∈ Word 𝐴𝐹 ∈ ℤ ∧ 𝐿 ∈ ℤ) → DECID (𝐹..^𝐿) ⊆ dom 𝑆)
 
19-Dec-2025ccatclab 11137 The concatenation of words over two sets is a word over the union of those sets. (Contributed by Jim Kingdon, 19-Dec-2025.)
((𝑆 ∈ Word 𝐴𝑇 ∈ Word 𝐵) → (𝑆 ++ 𝑇) ∈ Word (𝐴𝐵))
 
18-Dec-2025lswwrd 11126 Extract the last symbol of a word. (Contributed by Alexander van der Vekens, 18-Mar-2018.) (Revised by Jim Kingdon, 18-Dec-2025.)
(𝑊 ∈ Word 𝑉 → (lastS‘𝑊) = (𝑊‘((♯‘𝑊) − 1)))
 
14-Dec-20252strstrndx 13159 A constructed two-slot structure not depending on the hard-coded index value of the base set. (Contributed by Mario Carneiro, 29-Aug-2015.) (Revised by Jim Kingdon, 14-Dec-2025.)
𝐺 = {⟨(Base‘ndx), 𝐵⟩, ⟨𝑁, + ⟩}    &   (Base‘ndx) < 𝑁    &   𝑁 ∈ ℕ       ((𝐵𝑉+𝑊) → 𝐺 Struct ⟨(Base‘ndx), 𝑁⟩)
 
12-Dec-2025funiedgdm2vald 15841 The set of indexed edges of an extensible structure with (at least) two slots. (Contributed by AV, 22-Sep-2020.) (Revised by Jim Kingdon, 12-Dec-2025.)
𝐴 ∈ V    &   𝐵 ∈ V    &   (𝜑𝐺𝑋)    &   (𝜑 → Fun (𝐺 ∖ {∅}))    &   (𝜑𝐴𝐵)    &   (𝜑 → {𝐴, 𝐵} ⊆ dom 𝐺)       (𝜑 → (iEdg‘𝐺) = (.ef‘𝐺))
 
11-Dec-2025funvtxdm2vald 15840 The set of vertices of an extensible structure with (at least) two slots. (Contributed by AV, 22-Sep-2020.) (Revised by Jim Kingdon, 11-Dec-2025.)
𝐴 ∈ V    &   𝐵 ∈ V    &   (𝜑𝐺𝑋)    &   (𝜑 → Fun (𝐺 ∖ {∅}))    &   (𝜑𝐴𝐵)    &   (𝜑 → {𝐴, 𝐵} ⊆ dom 𝐺)       (𝜑 → (Vtx‘𝐺) = (Base‘𝐺))
 
11-Dec-2025funiedgdm2domval 15839 The set of indexed edges of an extensible structure with (at least) two slots. (Contributed by AV, 12-Oct-2020.) (Revised by Jim Kingdon, 11-Dec-2025.)
((𝐺𝑉 ∧ Fun (𝐺 ∖ {∅}) ∧ 2o ≼ dom 𝐺) → (iEdg‘𝐺) = (.ef‘𝐺))
 
11-Dec-2025funvtxdm2domval 15838 The set of vertices of an extensible structure with (at least) two slots. (Contributed by AV, 12-Oct-2020.) (Revised by Jim Kingdon, 11-Dec-2025.)
((𝐺𝑉 ∧ Fun (𝐺 ∖ {∅}) ∧ 2o ≼ dom 𝐺) → (Vtx‘𝐺) = (Base‘𝐺))
 
4-Dec-2025hash2en 11073 Two equivalent ways to say a set has two elements. (Contributed by Jim Kingdon, 4-Dec-2025.)
(𝑉 ≈ 2o ↔ (𝑉 ∈ Fin ∧ (♯‘𝑉) = 2))
 
30-Nov-2025nninfnfiinf 16419 An element of which is not finite is infinite. (Contributed by Jim Kingdon, 30-Nov-2025.)
((𝐴 ∈ ℕ ∧ ¬ ∃𝑛 ∈ ω 𝐴 = (𝑖 ∈ ω ↦ if(𝑖𝑛, 1o, ∅))) → 𝐴 = (𝑖 ∈ ω ↦ 1o))
 
27-Nov-2025psrelbasfi 14648 Simpler form of psrelbas 14647 when the index set is finite. (Contributed by Jim Kingdon, 27-Nov-2025.)
𝑆 = (𝐼 mPwSer 𝑅)    &   𝐾 = (Base‘𝑅)    &   (𝜑𝐼 ∈ Fin)    &   𝐵 = (Base‘𝑆)    &   (𝜑𝑋𝐵)       (𝜑𝑋:(ℕ0𝑚 𝐼)⟶𝐾)
 
26-Nov-2025mplsubgfileminv 14672 Lemma for mplsubgfi 14673. The additive inverse of a polynomial is a polynomial. (Contributed by Jim Kingdon, 26-Nov-2025.)
𝑆 = (𝐼 mPwSer 𝑅)    &   𝑃 = (𝐼 mPoly 𝑅)    &   𝑈 = (Base‘𝑃)    &   (𝜑𝐼 ∈ Fin)    &   (𝜑𝑅 ∈ Grp)    &   (𝜑𝑋𝑈)    &   𝑁 = (invg𝑆)       (𝜑 → (𝑁𝑋) ∈ 𝑈)
 
26-Nov-2025mplsubgfilemcl 14671 Lemma for mplsubgfi 14673. The sum of two polynomials is a polynomial. (Contributed by Jim Kingdon, 26-Nov-2025.)
𝑆 = (𝐼 mPwSer 𝑅)    &   𝑃 = (𝐼 mPoly 𝑅)    &   𝑈 = (Base‘𝑃)    &   (𝜑𝐼 ∈ Fin)    &   (𝜑𝑅 ∈ Grp)    &   (𝜑𝑋𝑈)    &   (𝜑𝑌𝑈)    &    + = (+g𝑆)       (𝜑 → (𝑋 + 𝑌) ∈ 𝑈)
 
25-Nov-2025nninfinfwlpo 7355 The point at infinity in being isolated is equivalent to the Weak Limited Principle of Omniscience (WLPO). By isolated, we mean that the equality of that point with every other element of is decidable. From an online post by Martin Escardo. By contrast, elements of corresponding to natural numbers are isolated (nninfisol 7308). (Contributed by Jim Kingdon, 25-Nov-2025.)
(∀𝑥 ∈ ℕ DECID 𝑥 = (𝑖 ∈ ω ↦ 1o) ↔ ω ∈ WOmni)
 
23-Nov-2025psrbagfi 14645 A finite index set gives a simpler expression for finite bags. (Contributed by Jim Kingdon, 23-Nov-2025.)
𝐷 = {𝑓 ∈ (ℕ0𝑚 𝐼) ∣ (𝑓 “ ℕ) ∈ Fin}       (𝐼 ∈ Fin → 𝐷 = (ℕ0𝑚 𝐼))
 
22-Nov-2025df-acnm 7360 Define a local and length-limited version of the axiom of choice. The definition of the predicate 𝑋AC 𝐴 is that for all families of inhabited subsets of 𝑋 indexed on 𝐴 (i.e. functions 𝐴⟶{𝑧 ∈ 𝒫 𝑋 ∣ ∃𝑗𝑗𝑧}), there is a function which selects an element from each set in the family. (Contributed by Mario Carneiro, 31-Aug-2015.) Change nonempty to inhabited. (Revised by Jim Kingdon, 22-Nov-2025.)
AC 𝐴 = {𝑥 ∣ (𝐴 ∈ V ∧ ∀𝑓 ∈ ({𝑧 ∈ 𝒫 𝑥 ∣ ∃𝑗 𝑗𝑧} ↑𝑚 𝐴)∃𝑔𝑦𝐴 (𝑔𝑦) ∈ (𝑓𝑦))}
 
21-Nov-2025mplsubgfilemm 14670 Lemma for mplsubgfi 14673. There exists a polynomial. (Contributed by Jim Kingdon, 21-Nov-2025.)
𝑆 = (𝐼 mPwSer 𝑅)    &   𝑃 = (𝐼 mPoly 𝑅)    &   𝑈 = (Base‘𝑃)    &   (𝜑𝐼 ∈ Fin)    &   (𝜑𝑅 ∈ Grp)       (𝜑 → ∃𝑗 𝑗𝑈)
 
14-Nov-20252omapen 16389 Equinumerosity of (2o𝑚 𝐴) and the set of decidable subsets of 𝐴. (Contributed by Jim Kingdon, 14-Nov-2025.)
(𝐴𝑉 → (2o𝑚 𝐴) ≈ {𝑥 ∈ 𝒫 𝐴 ∣ ∀𝑦𝐴 DECID 𝑦𝑥})
 
12-Nov-20252omap 16388 Mapping between (2o𝑚 𝐴) and decidable subsets of 𝐴. (Contributed by Jim Kingdon, 12-Nov-2025.)
𝐹 = (𝑠 ∈ (2o𝑚 𝐴) ↦ {𝑧𝐴 ∣ (𝑠𝑧) = 1o})       (𝐴𝑉𝐹:(2o𝑚 𝐴)–1-1-onto→{𝑥 ∈ 𝒫 𝐴 ∣ ∀𝑦𝐴 DECID 𝑦𝑥})
 
11-Nov-2025domomsubct 16396 A set dominated by ω is subcountable. (Contributed by Jim Kingdon, 11-Nov-2025.)
(𝐴 ≼ ω → ∃𝑠(𝑠 ⊆ ω ∧ ∃𝑓 𝑓:𝑠onto𝐴))
 
10-Nov-2025prdsbaslemss 13315 Lemma for prdsbas 13317 and similar theorems. (Contributed by Jim Kingdon, 10-Nov-2025.)
𝑃 = (𝑆Xs𝑅)    &   (𝜑𝑆𝑉)    &   (𝜑𝑅𝑊)    &   𝐴 = (𝐸𝑃)    &   𝐸 = Slot (𝐸‘ndx)    &   (𝐸‘ndx) ∈ ℕ    &   (𝜑𝑇𝑋)    &   (𝜑 → {⟨(𝐸‘ndx), 𝑇⟩} ⊆ 𝑃)       (𝜑𝐴 = 𝑇)
 
5-Nov-2025fnmpl 14665 mPoly has universal domain. (Contributed by Jim Kingdon, 5-Nov-2025.)
mPoly Fn (V × V)
 
4-Nov-2025mplelbascoe 14664 Property of being a polynomial. (Contributed by Mario Carneiro, 7-Jan-2015.) (Revised by Mario Carneiro, 2-Oct-2015.) (Revised by AV, 25-Jun-2019.) (Revised by Jim Kingdon, 4-Nov-2025.)
𝑃 = (𝐼 mPoly 𝑅)    &   𝑆 = (𝐼 mPwSer 𝑅)    &   𝐵 = (Base‘𝑆)    &    0 = (0g𝑅)    &   𝑈 = (Base‘𝑃)       ((𝐼𝑉𝑅𝑊) → (𝑋𝑈 ↔ (𝑋𝐵 ∧ ∃𝑎 ∈ (ℕ0𝑚 𝐼)∀𝑏 ∈ (ℕ0𝑚 𝐼)(∀𝑘𝐼 (𝑎𝑘) < (𝑏𝑘) → (𝑋𝑏) = 0 ))))
 
4-Nov-2025mplbascoe 14663 Base set of the set of multivariate polynomials. (Contributed by Mario Carneiro, 7-Jan-2015.) (Revised by AV, 25-Jun-2019.) (Revised by Jim Kingdon, 4-Nov-2025.)
𝑃 = (𝐼 mPoly 𝑅)    &   𝑆 = (𝐼 mPwSer 𝑅)    &   𝐵 = (Base‘𝑆)    &    0 = (0g𝑅)    &   𝑈 = (Base‘𝑃)       ((𝐼𝑉𝑅𝑊) → 𝑈 = {𝑓𝐵 ∣ ∃𝑎 ∈ (ℕ0𝑚 𝐼)∀𝑏 ∈ (ℕ0𝑚 𝐼)(∀𝑘𝐼 (𝑎𝑘) < (𝑏𝑘) → (𝑓𝑏) = 0 )})
 
4-Nov-2025mplvalcoe 14662 Value of the set of multivariate polynomials. (Contributed by Mario Carneiro, 7-Jan-2015.) (Revised by AV, 25-Jun-2019.) (Revised by Jim Kingdon, 4-Nov-2025.)
𝑃 = (𝐼 mPoly 𝑅)    &   𝑆 = (𝐼 mPwSer 𝑅)    &   𝐵 = (Base‘𝑆)    &    0 = (0g𝑅)    &   𝑈 = {𝑓𝐵 ∣ ∃𝑎 ∈ (ℕ0𝑚 𝐼)∀𝑏 ∈ (ℕ0𝑚 𝐼)(∀𝑘𝐼 (𝑎𝑘) < (𝑏𝑘) → (𝑓𝑏) = 0 )}       ((𝐼𝑉𝑅𝑊) → 𝑃 = (𝑆s 𝑈))
 
1-Nov-2025ficardon 7369 The cardinal number of a finite set is an ordinal. (Contributed by Jim Kingdon, 1-Nov-2025.)
(𝐴 ∈ Fin → (card‘𝐴) ∈ On)
 
31-Oct-2025bitsdc 12466 Whether a bit is set is decidable. (Contributed by Jim Kingdon, 31-Oct-2025.)
((𝑁 ∈ ℤ ∧ 𝑀 ∈ ℕ0) → DECID 𝑀 ∈ (bits‘𝑁))
 
28-Oct-2025nn0maxcl 11744 The maximum of two nonnegative integers is a nonnegative integer. (Contributed by Jim Kingdon, 28-Oct-2025.)
((𝐴 ∈ ℕ0𝐵 ∈ ℕ0) → sup({𝐴, 𝐵}, ℝ, < ) ∈ ℕ0)
 
28-Oct-2025qdcle 10474 Rational is decidable. (Contributed by Jim Kingdon, 28-Oct-2025.)
((𝐴 ∈ ℚ ∧ 𝐵 ∈ ℚ) → DECID 𝐴𝐵)
 
17-Oct-2025plycoeid3 15439 Reconstruct a polynomial as an explicit sum of the coefficient function up to an index no smaller than the degree of the polynomial. (Contributed by Jim Kingdon, 17-Oct-2025.)
(𝜑𝐷 ∈ ℕ0)    &   (𝜑𝐴:ℕ0⟶ℂ)    &   (𝜑 → (𝐴 “ (ℤ‘(𝐷 + 1))) = {0})    &   (𝜑𝐹 = (𝑧 ∈ ℂ ↦ Σ𝑘 ∈ (0...𝐷)((𝐴𝑘) · (𝑧𝑘))))    &   (𝜑𝑀 ∈ (ℤ𝐷))    &   (𝜑𝑋 ∈ ℂ)       (𝜑 → (𝐹𝑋) = Σ𝑗 ∈ (0...𝑀)((𝐴𝑗) · (𝑋𝑗)))
 
13-Oct-2025tpfidceq 7100 A triple is finite if it consists of elements of a class with decidable equality. (Contributed by Jim Kingdon, 13-Oct-2025.)
(𝜑𝐴𝐷)    &   (𝜑𝐵𝐷)    &   (𝜑𝐶𝐷)    &   (𝜑 → ∀𝑥𝐷𝑦𝐷 DECID 𝑥 = 𝑦)       (𝜑 → {𝐴, 𝐵, 𝐶} ∈ Fin)
 
13-Oct-2025prfidceq 7098 A pair is finite if it consists of elements of a class with decidable equality. (Contributed by Jim Kingdon, 13-Oct-2025.)
(𝜑𝐴𝐶)    &   (𝜑𝐵𝐶)    &   (𝜑 → ∀𝑥𝐶𝑦𝐶 DECID 𝑥 = 𝑦)       (𝜑 → {𝐴, 𝐵} ∈ Fin)
 
13-Oct-2025dcun 3601 The union of two decidable classes is decidable. (Contributed by Jim Kingdon, 5-Oct-2022.) (Revised by Jim Kingdon, 13-Oct-2025.)
(𝜑DECID 𝐶𝐴)    &   (𝜑DECID 𝐶𝐵)       (𝜑DECID 𝐶 ∈ (𝐴𝐵))
 
9-Oct-2025dvdsfi 12769 A natural number has finitely many divisors. (Contributed by Jim Kingdon, 9-Oct-2025.)
(𝑁 ∈ ℕ → {𝑥 ∈ ℕ ∣ 𝑥𝑁} ∈ Fin)
 
7-Oct-2025df-mplcoe 14636 Define the subalgebra of the power series algebra generated by the variables; this is the polynomial algebra (the set of power series with finite degree).

The index set (which has an element for each variable) is 𝑖, the coefficients are in ring 𝑟, and for each variable there is a "degree" such that the coefficient is zero for a term where the powers are all greater than those degrees. (Degree is in quotes because there is no guarantee that coefficients below that degree are nonzero, as we do not assume decidable equality for 𝑟). (Contributed by Mario Carneiro, 7-Jan-2015.) (Revised by AV, 25-Jun-2019.) (Revised by Jim Kingdon, 7-Oct-2025.)

mPoly = (𝑖 ∈ V, 𝑟 ∈ V ↦ (𝑖 mPwSer 𝑟) / 𝑤(𝑤s {𝑓 ∈ (Base‘𝑤) ∣ ∃𝑎 ∈ (ℕ0𝑚 𝑖)∀𝑏 ∈ (ℕ0𝑚 𝑖)(∀𝑘𝑖 (𝑎𝑘) < (𝑏𝑘) → (𝑓𝑏) = (0g𝑟))}))
 
6-Oct-2025dvconstss 15380 Derivative of a constant function defined on an open set. (Contributed by Jim Kingdon, 6-Oct-2025.)
(𝜑𝑆 ∈ {ℝ, ℂ})    &   𝐽 = (𝐾t 𝑆)    &   𝐾 = (MetOpen‘(abs ∘ − ))    &   (𝜑𝑋𝐽)    &   (𝜑𝐴 ∈ ℂ)       (𝜑 → (𝑆 D (𝑋 × {𝐴})) = (𝑋 × {0}))
 
6-Oct-2025dcfrompeirce 1492 The decidability of a proposition 𝜒 follows from a suitable instance of Peirce's law. Therefore, if we were to introduce Peirce's law as a general principle (without the decidability condition in peircedc 919), then we could prove that every proposition is decidable, giving us the classical system of propositional calculus (since Perice's law is itself classically valid). (Contributed by Adrian Ducourtial, 6-Oct-2025.)
(𝜑 ↔ (𝜒 ∨ ¬ 𝜒))    &   (𝜓 ↔ ⊥)    &   (((𝜑𝜓) → 𝜑) → 𝜑)       DECID 𝜒
 
6-Oct-2025dcfromcon 1491 The decidability of a proposition 𝜒 follows from a suitable instance of the principle of contraposition. Therefore, if we were to introduce contraposition as a general principle (without the decidability condition in condc 858), then we could prove that every proposition is decidable, giving us the classical system of propositional calculus (since the principle of contraposition is itself classically valid). (Contributed by Adrian Ducourtial, 6-Oct-2025.)
(𝜑 ↔ (𝜒 ∨ ¬ 𝜒))    &   (𝜓 ↔ ⊤)    &   ((¬ 𝜑 → ¬ 𝜓) → (𝜓𝜑))       DECID 𝜒
 
6-Oct-2025dcfromnotnotr 1490 The decidability of a proposition 𝜓 follows from a suitable instance of double negation elimination (DNE). Therefore, if we were to introduce DNE as a general principle (without the decidability condition in notnotrdc 848), then we could prove that every proposition is decidable, giving us the classical system of propositional calculus (since DNE itself is classically valid). (Contributed by Adrian Ducourtial, 6-Oct-2025.)
(𝜑 ↔ (𝜓 ∨ ¬ 𝜓))    &   (¬ ¬ 𝜑𝜑)       DECID 𝜓
 
3-Oct-2025dvidre 15379 Real derivative of the identity function. (Contributed by Jim Kingdon, 3-Oct-2025.)
(ℝ D ( I ↾ ℝ)) = (ℝ × {1})
 
3-Oct-2025dvconstre 15378 Real derivative of a constant function. (Contributed by Jim Kingdon, 3-Oct-2025.)
(𝐴 ∈ ℂ → (ℝ D (ℝ × {𝐴})) = (ℝ × {0}))
 
3-Oct-2025dvidsslem 15375 Lemma for dvconstss 15380. Analogue of dvidlemap 15373 where 𝐹 is defined on an open subset of the real or complex numbers. (Contributed by Jim Kingdon, 3-Oct-2025.)
(𝜑𝑆 ∈ {ℝ, ℂ})    &   𝐽 = (𝐾t 𝑆)    &   𝐾 = (MetOpen‘(abs ∘ − ))    &   (𝜑𝐹:𝑋⟶ℂ)    &   (𝜑𝑋𝐽)    &   ((𝜑 ∧ (𝑥𝑋𝑧𝑋𝑧 # 𝑥)) → (((𝐹𝑧) − (𝐹𝑥)) / (𝑧𝑥)) = 𝐵)    &   𝐵 ∈ ℂ       (𝜑 → (𝑆 D 𝐹) = (𝑋 × {𝐵}))
 
3-Oct-2025dvidrelem 15374 Lemma for dvidre 15379 and dvconstre 15378. Analogue of dvidlemap 15373 for real numbers rather than complex numbers. (Contributed by Jim Kingdon, 3-Oct-2025.)
(𝜑𝐹:ℝ⟶ℂ)    &   ((𝜑 ∧ (𝑥 ∈ ℝ ∧ 𝑧 ∈ ℝ ∧ 𝑧 # 𝑥)) → (((𝐹𝑧) − (𝐹𝑥)) / (𝑧𝑥)) = 𝐵)    &   𝐵 ∈ ℂ       (𝜑 → (ℝ D 𝐹) = (ℝ × {𝐵}))
 
28-Sep-2025metuex 14527 Applying metUnif yields a set. (Contributed by Jim Kingdon, 28-Sep-2025.)
(𝐴𝑉 → (metUnif‘𝐴) ∈ V)
 
28-Sep-2025cndsex 14525 The standard distance function on the complex numbers is a set. (Contributed by Jim Kingdon, 28-Sep-2025.)
(abs ∘ − ) ∈ V
 
25-Sep-2025cntopex 14526 The standard topology on the complex numbers is a set. (Contributed by Jim Kingdon, 25-Sep-2025.)
(MetOpen‘(abs ∘ − )) ∈ V
 
24-Sep-2025mopnset 14524 Getting a set by applying MetOpen. (Contributed by Jim Kingdon, 24-Sep-2025.)
(𝐷𝑉 → (MetOpen‘𝐷) ∈ V)
 
24-Sep-2025blfn 14523 The ball function has universal domain. (Contributed by Jim Kingdon, 24-Sep-2025.)
ball Fn V
 
23-Sep-2025elfzoext 10406 Membership of an integer in an extended open range of integers, extension added to the right. (Contributed by AV, 30-Apr-2020.) (Proof shortened by AV, 23-Sep-2025.)
((𝑍 ∈ (𝑀..^𝑁) ∧ 𝐼 ∈ ℕ0) → 𝑍 ∈ (𝑀..^(𝑁 + 𝐼)))
 
22-Sep-2025plycjlemc 15442 Lemma for plycj 15443. (Contributed by Mario Carneiro, 24-Jul-2014.) (Revised by Jim Kingdon, 22-Sep-2025.)
(𝜑𝑁 ∈ ℕ0)    &   𝐺 = ((∗ ∘ 𝐹) ∘ ∗)    &   (𝜑𝐴:ℕ0⟶(𝑆 ∪ {0}))    &   (𝜑𝐹 = (𝑧 ∈ ℂ ↦ Σ𝑘 ∈ (0...𝑁)((𝐴𝑘) · (𝑧𝑘))))    &   (𝜑𝐹 ∈ (Poly‘𝑆))       (𝜑𝐺 = (𝑧 ∈ ℂ ↦ Σ𝑘 ∈ (0...𝑁)(((∗ ∘ 𝐴)‘𝑘) · (𝑧𝑘))))
 
20-Sep-2025plycolemc 15440 Lemma for plyco 15441. The result expressed as a sum, with a degree and coefficients for 𝐹 specified as hypotheses. (Contributed by Jim Kingdon, 20-Sep-2025.)
(𝜑𝐹 ∈ (Poly‘𝑆))    &   (𝜑𝐺 ∈ (Poly‘𝑆))    &   ((𝜑 ∧ (𝑥𝑆𝑦𝑆)) → (𝑥 + 𝑦) ∈ 𝑆)    &   ((𝜑 ∧ (𝑥𝑆𝑦𝑆)) → (𝑥 · 𝑦) ∈ 𝑆)    &   (𝜑𝑁 ∈ ℕ0)    &   (𝜑𝐴:ℕ0⟶(𝑆 ∪ {0}))    &   (𝜑 → (𝐴 “ (ℤ‘(𝑁 + 1))) = {0})    &   (𝜑𝐹 = (𝑥 ∈ ℂ ↦ Σ𝑘 ∈ (0...𝑁)((𝐴𝑘) · (𝑥𝑘))))       (𝜑 → (𝑧 ∈ ℂ ↦ Σ𝑘 ∈ (0...𝑁)((𝐴𝑘) · ((𝐺𝑧)↑𝑘))) ∈ (Poly‘𝑆))

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