HomeTheorem List (p. 279 of 498)
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| Type | Label | Description |
|---|---|---|
| Statement | ||
| Theorem | oldirr 27801 | No surreal is a member of its birthday's old set. (Contributed by Scott Fenton, 10-Aug-2024.) |
| ⊢ ¬ 𝑋 ∈ ( O ‘( bday ‘𝑋)) | ||
| Theorem | leftirr 27802 | No surreal is a member of its left set. (Contributed by Scott Fenton, 9-Oct-2024.) |
| ⊢ ¬ 𝑋 ∈ ( L ‘𝑋) | ||
| Theorem | rightirr 27803 | No surreal is a member of its right set. (Contributed by Scott Fenton, 9-Oct-2024.) |
| ⊢ ¬ 𝑋 ∈ ( R ‘𝑋) | ||
| Theorem | left0s 27804 | The left set of 0s is empty. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ ( L ‘ 0s ) = ∅ | ||
| Theorem | right0s 27805 | The right set of 0s is empty. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ ( R ‘ 0s ) = ∅ | ||
| Theorem | left1s 27806 | The left set of 1s is the singleton of 0s. (Contributed by Scott Fenton, 4-Feb-2025.) |
| ⊢ ( L ‘ 1s ) = { 0s } | ||
| Theorem | right1s 27807 | The right set of 1s is empty . (Contributed by Scott Fenton, 4-Feb-2025.) |
| ⊢ ( R ‘ 1s ) = ∅ | ||
| Theorem | lrold 27808 | The union of the left and right options of a surreal make its old set. (Contributed by Scott Fenton, 9-Oct-2024.) |
| ⊢ (( L ‘𝐴) ∪ ( R ‘𝐴)) = ( O ‘( bday ‘𝐴)) | ||
| Theorem | madebdaylemold 27809* | Lemma for madebday 27811. If the inductive hypothesis of madebday 27811 is satisfied, the converse of oldbdayim 27800 holds. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ ((𝐴 ∈ On ∧ ∀𝑏 ∈ 𝐴 ∀𝑦 ∈ No (( bday ‘𝑦) ⊆ 𝑏 → 𝑦 ∈ ( M ‘𝑏)) ∧ 𝑋 ∈ No ) → (( bday ‘𝑋) ∈ 𝐴 → 𝑋 ∈ ( O ‘𝐴))) | ||
| Theorem | madebdaylemlrcut 27810* | Lemma for madebday 27811. If the inductive hypothesis of madebday 27811 is satisfied up to the birthday of 𝑋, then the conclusion of lrcut 27815 holds. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ ((∀𝑏 ∈ ( bday ‘𝑋)∀𝑦 ∈ No (( bday ‘𝑦) ⊆ 𝑏 → 𝑦 ∈ ( M ‘𝑏)) ∧ 𝑋 ∈ No ) → (( L ‘𝑋) |s ( R ‘𝑋)) = 𝑋) | ||
| Theorem | madebday 27811 | A surreal is part of the set made by ordinal 𝐴 iff its birthday is less than or equal to 𝐴. Remark in [Conway] p. 29. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ ((𝐴 ∈ On ∧ 𝑋 ∈ No ) → (𝑋 ∈ ( M ‘𝐴) ↔ ( bday ‘𝑋) ⊆ 𝐴)) | ||
| Theorem | oldbday 27812 | A surreal is part of the set older than ordinal 𝐴 iff its birthday is less than 𝐴. Remark in [Conway] p. 29. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ ((𝐴 ∈ On ∧ 𝑋 ∈ No ) → (𝑋 ∈ ( O ‘𝐴) ↔ ( bday ‘𝑋) ∈ 𝐴)) | ||
| Theorem | newbday 27813 | A surreal is an element of a new set iff its birthday is equal to that ordinal. Remark in [Conway] p. 29. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ ((𝐴 ∈ On ∧ 𝑋 ∈ No ) → (𝑋 ∈ ( N ‘𝐴) ↔ ( bday ‘𝑋) = 𝐴)) | ||
| Theorem | newbdayim 27814 | One direction of the biconditional in newbday 27813. (Contributed by Scott Fenton, 7-Nov-2025.) |
| ⊢ (𝑋 ∈ ( N ‘𝐴) → ( bday ‘𝑋) = 𝐴) | ||
| Theorem | lrcut 27815 | A surreal is equal to the cut of its left and right sets. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ (𝑋 ∈ No → (( L ‘𝑋) |s ( R ‘𝑋)) = 𝑋) | ||
| Theorem | scutfo 27816 | The surreal cut function is onto. (Contributed by Scott Fenton, 23-Aug-2024.) |
| ⊢ |s : <<s –onto→ No | ||
| Theorem | sltn0 27817 | If 𝑋 is less than 𝑌, then either ( L ‘𝑌) or ( R ‘𝑋) is non-empty. (Contributed by Scott Fenton, 10-Dec-2024.) |
| ⊢ ((𝑋 ∈ No ∧ 𝑌 ∈ No ∧ 𝑋 <s 𝑌) → (( L ‘𝑌) ≠ ∅ ∨ ( R ‘𝑋) ≠ ∅)) | ||
| Theorem | lruneq 27818 | If two surreals share a birthday, then the union of their left and right sets are equal. (Contributed by Scott Fenton, 17-Sep-2024.) |
| ⊢ ((𝑋 ∈ No ∧ 𝑌 ∈ No ∧ ( bday ‘𝑋) = ( bday ‘𝑌)) → (( L ‘𝑋) ∪ ( R ‘𝑋)) = (( L ‘𝑌) ∪ ( R ‘𝑌))) | ||
| Theorem | sltlpss 27819 | If two surreals share a birthday, then 𝑋 <s 𝑌 iff the left set of 𝑋 is a proper subset of the left set of 𝑌. (Contributed by Scott Fenton, 17-Sep-2024.) |
| ⊢ ((𝑋 ∈ No ∧ 𝑌 ∈ No ∧ ( bday ‘𝑋) = ( bday ‘𝑌)) → (𝑋 <s 𝑌 ↔ ( L ‘𝑋) ⊊ ( L ‘𝑌))) | ||
| Theorem | slelss 27820 | If two surreals 𝐴 and 𝐵 share a birthday, then 𝐴 ≤s 𝐵 if and only if the left set of 𝐴 is a non-strict subset of the left set of 𝐵. (Contributed by Scott Fenton, 21-Mar-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ∧ ( bday ‘𝐴) = ( bday ‘𝐵)) → (𝐴 ≤s 𝐵 ↔ ( L ‘𝐴) ⊆ ( L ‘𝐵))) | ||
| Theorem | 0elold 27821 | Zero is in the old set of any non-zero number. (Contributed by Scott Fenton, 13-Mar-2025.) |
| ⊢ (𝜑 → 𝐴 ∈ No ) & ⊢ (𝜑 → 𝐴 ≠ 0s ) ⇒ ⊢ (𝜑 → 0s ∈ ( O ‘( bday ‘𝐴))) | ||
| Theorem | 0elleft 27822 | Zero is in the left set of any positive number. (Contributed by Scott Fenton, 13-Mar-2025.) |
| ⊢ (𝜑 → 𝐴 ∈ No ) & ⊢ (𝜑 → 0s <s 𝐴) ⇒ ⊢ (𝜑 → 0s ∈ ( L ‘𝐴)) | ||
| Theorem | 0elright 27823 | Zero is in the right set of any negative number. (Contributed by Scott Fenton, 13-Mar-2025.) |
| ⊢ (𝜑 → 𝐴 ∈ No ) & ⊢ (𝜑 → 𝐴 <s 0s ) ⇒ ⊢ (𝜑 → 0s ∈ ( R ‘𝐴)) | ||
| Theorem | madefi 27824 | The made set of an ordinal natural is finite. (Contributed by Scott Fenton, 20-Aug-2025.) |
| ⊢ (𝐴 ∈ ω → ( M ‘𝐴) ∈ Fin) | ||
| Theorem | oldfi 27825 | The old set of an ordinal natural is finite. (Contributed by Scott Fenton, 20-Aug-2025.) |
| ⊢ (𝐴 ∈ ω → ( O ‘𝐴) ∈ Fin) | ||
| Theorem | cofsslt 27826* | If every element of 𝐴 is bounded above by some element of 𝐵 and 𝐵 precedes 𝐶, then 𝐴 precedes 𝐶. Note - we will often use the term "cofinal" to denote that every element of 𝐴 is bounded above by some element of 𝐵. Similarly, we will use the term "coinitial" to denote that every element of 𝐴 is bounded below by some element of 𝐵. (Contributed by Scott Fenton, 24-Sep-2024.) |
| ⊢ ((𝐴 ∈ 𝒫 No ∧ ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐵 𝑥 ≤s 𝑦 ∧ 𝐵 <<s 𝐶) → 𝐴 <<s 𝐶) | ||
| Theorem | coinitsslt 27827* | If 𝐵 is coinitial with 𝐶 and 𝐴 precedes 𝐶, then 𝐴 precedes 𝐵. (Contributed by Scott Fenton, 24-Sep-2024.) |
| ⊢ ((𝐵 ∈ 𝒫 No ∧ ∀𝑥 ∈ 𝐵 ∃𝑦 ∈ 𝐶 𝑦 ≤s 𝑥 ∧ 𝐴 <<s 𝐶) → 𝐴 <<s 𝐵) | ||
| Theorem | cofcut1 27828* | If 𝐶 is cofinal with 𝐴 and 𝐷 is coinitial with 𝐵 and the cut of 𝐴 and 𝐵 lies between 𝐶 and 𝐷, then the cut of 𝐶 and 𝐷 is equal to the cut of 𝐴 and 𝐵. Theorem 2.6 of [Gonshor] p. 10. (Contributed by Scott Fenton, 25-Sep-2024.) |
| ⊢ ((𝐴 <<s 𝐵 ∧ (∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐶 𝑥 ≤s 𝑦 ∧ ∀𝑧 ∈ 𝐵 ∃𝑤 ∈ 𝐷 𝑤 ≤s 𝑧) ∧ (𝐶 <<s {(𝐴 |s 𝐵)} ∧ {(𝐴 |s 𝐵)} <<s 𝐷)) → (𝐴 |s 𝐵) = (𝐶 |s 𝐷)) | ||
| Theorem | cofcut1d 27829* | If 𝐶 is cofinal with 𝐴 and 𝐷 is coinitial with 𝐵 and the cut of 𝐴 and 𝐵 lies between 𝐶 and 𝐷, then the cut of 𝐶 and 𝐷 is equal to the cut of 𝐴 and 𝐵. Theorem 2.6 of [Gonshor] p. 10. (Contributed by Scott Fenton, 23-Jan-2025.) |
| ⊢ (𝜑 → 𝐴 <<s 𝐵) & ⊢ (𝜑 → ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐶 𝑥 ≤s 𝑦) & ⊢ (𝜑 → ∀𝑧 ∈ 𝐵 ∃𝑤 ∈ 𝐷 𝑤 ≤s 𝑧) & ⊢ (𝜑 → 𝐶 <<s {(𝐴 |s 𝐵)}) & ⊢ (𝜑 → {(𝐴 |s 𝐵)} <<s 𝐷) ⇒ ⊢ (𝜑 → (𝐴 |s 𝐵) = (𝐶 |s 𝐷)) | ||
| Theorem | cofcut2 27830* | If 𝐴 and 𝐶 are mutually cofinal and 𝐵 and 𝐷 are mutually coinitial, then the cut of 𝐴 and 𝐵 is equal to the cut of 𝐶 and 𝐷. Theorem 2.7 of [Gonshor] p. 10. (Contributed by Scott Fenton, 25-Sep-2024.) |
| ⊢ (((𝐴 <<s 𝐵 ∧ 𝐶 ∈ 𝒫 No ∧ 𝐷 ∈ 𝒫 No ) ∧ (∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐶 𝑥 ≤s 𝑦 ∧ ∀𝑧 ∈ 𝐵 ∃𝑤 ∈ 𝐷 𝑤 ≤s 𝑧) ∧ (∀𝑡 ∈ 𝐶 ∃𝑢 ∈ 𝐴 𝑡 ≤s 𝑢 ∧ ∀𝑟 ∈ 𝐷 ∃𝑠 ∈ 𝐵 𝑠 ≤s 𝑟)) → (𝐴 |s 𝐵) = (𝐶 |s 𝐷)) | ||
| Theorem | cofcut2d 27831* | If 𝐴 and 𝐶 are mutually cofinal and 𝐵 and 𝐷 are mutually coinitial, then the cut of 𝐴 and 𝐵 is equal to the cut of 𝐶 and 𝐷. Theorem 2.7 of [Gonshor] p. 10. (Contributed by Scott Fenton, 23-Jan-2025.) |
| ⊢ (𝜑 → 𝐴 <<s 𝐵) & ⊢ (𝜑 → 𝐶 ∈ 𝒫 No ) & ⊢ (𝜑 → 𝐷 ∈ 𝒫 No ) & ⊢ (𝜑 → ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ 𝐶 𝑥 ≤s 𝑦) & ⊢ (𝜑 → ∀𝑧 ∈ 𝐵 ∃𝑤 ∈ 𝐷 𝑤 ≤s 𝑧) & ⊢ (𝜑 → ∀𝑡 ∈ 𝐶 ∃𝑢 ∈ 𝐴 𝑡 ≤s 𝑢) & ⊢ (𝜑 → ∀𝑟 ∈ 𝐷 ∃𝑠 ∈ 𝐵 𝑠 ≤s 𝑟) ⇒ ⊢ (𝜑 → (𝐴 |s 𝐵) = (𝐶 |s 𝐷)) | ||
| Theorem | cofcutr 27832* | If 𝑋 is the cut of 𝐴 and 𝐵, then 𝐴 is cofinal with ( L ‘𝑋) and 𝐵 is coinitial with ( R ‘𝑋). Theorem 2.9 of [Gonshor] p. 12. (Contributed by Scott Fenton, 25-Sep-2024.) |
| ⊢ ((𝐴 <<s 𝐵 ∧ 𝑋 = (𝐴 |s 𝐵)) → (∀𝑥 ∈ ( L ‘𝑋)∃𝑦 ∈ 𝐴 𝑥 ≤s 𝑦 ∧ ∀𝑧 ∈ ( R ‘𝑋)∃𝑤 ∈ 𝐵 𝑤 ≤s 𝑧)) | ||
| Theorem | cofcutr1d 27833* | If 𝑋 is the cut of 𝐴 and 𝐵, then 𝐴 is cofinal with ( L ‘𝑋). First half of theorem 2.9 of [Gonshor] p. 12. (Contributed by Scott Fenton, 23-Jan-2025.) |
| ⊢ (𝜑 → 𝐴 <<s 𝐵) & ⊢ (𝜑 → 𝑋 = (𝐴 |s 𝐵)) ⇒ ⊢ (𝜑 → ∀𝑥 ∈ ( L ‘𝑋)∃𝑦 ∈ 𝐴 𝑥 ≤s 𝑦) | ||
| Theorem | cofcutr2d 27834* | If 𝑋 is the cut of 𝐴 and 𝐵, then 𝐵 is coinitial with ( R ‘𝑋). Second half of theorem 2.9 of [Gonshor] p. 12. (Contributed by Scott Fenton, 25-Sep-2024.) |
| ⊢ (𝜑 → 𝐴 <<s 𝐵) & ⊢ (𝜑 → 𝑋 = (𝐴 |s 𝐵)) ⇒ ⊢ (𝜑 → ∀𝑧 ∈ ( R ‘𝑋)∃𝑤 ∈ 𝐵 𝑤 ≤s 𝑧) | ||
| Theorem | cofcutrtime 27835* | If 𝑋 is the cut of 𝐴 and 𝐵 and all of 𝐴 and 𝐵 are older than 𝑋, then ( L ‘𝑋) is cofinal with 𝐴 and ( R ‘𝑋) is coinitial with 𝐵. Note: we will call a cut where all of the elements of the cut are older than the cut itself a "timely" cut. Part of Theorem 4.02(12) of [Alling] p. 125. (Contributed by Scott Fenton, 27-Sep-2024.) |
| ⊢ (((𝐴 ∪ 𝐵) ⊆ ( O ‘( bday ‘𝑋)) ∧ 𝐴 <<s 𝐵 ∧ 𝑋 = (𝐴 |s 𝐵)) → (∀𝑥 ∈ 𝐴 ∃𝑦 ∈ ( L ‘𝑋)𝑥 ≤s 𝑦 ∧ ∀𝑧 ∈ 𝐵 ∃𝑤 ∈ ( R ‘𝑋)𝑤 ≤s 𝑧)) | ||
| Theorem | cofcutrtime1d 27836* | If 𝑋 is a timely cut of 𝐴 and 𝐵, then ( L ‘𝑋) is cofinal with 𝐴. (Contributed by Scott Fenton, 23-Jan-2025.) |
| ⊢ (𝜑 → (𝐴 ∪ 𝐵) ⊆ ( O ‘( bday ‘𝑋))) & ⊢ (𝜑 → 𝐴 <<s 𝐵) & ⊢ (𝜑 → 𝑋 = (𝐴 |s 𝐵)) ⇒ ⊢ (𝜑 → ∀𝑥 ∈ 𝐴 ∃𝑦 ∈ ( L ‘𝑋)𝑥 ≤s 𝑦) | ||
| Theorem | cofcutrtime2d 27837* | If 𝑋 is a timely cut of 𝐴 and 𝐵, then ( R ‘𝑋) is coinitial with 𝐵. (Contributed by Scott Fenton, 23-Jan-2025.) |
| ⊢ (𝜑 → (𝐴 ∪ 𝐵) ⊆ ( O ‘( bday ‘𝑋))) & ⊢ (𝜑 → 𝐴 <<s 𝐵) & ⊢ (𝜑 → 𝑋 = (𝐴 |s 𝐵)) ⇒ ⊢ (𝜑 → ∀𝑧 ∈ 𝐵 ∃𝑤 ∈ ( R ‘𝑋)𝑤 ≤s 𝑧) | ||
| Theorem | cofss 27838* | Cofinality for a subset. (Contributed by Scott Fenton, 13-Mar-2025.) |
| ⊢ (𝜑 → 𝐴 ⊆ No ) & ⊢ (𝜑 → 𝐵 ⊆ 𝐴) ⇒ ⊢ (𝜑 → ∀𝑥 ∈ 𝐵 ∃𝑦 ∈ 𝐴 𝑥 ≤s 𝑦) | ||
| Theorem | coiniss 27839* | Coinitiality for a subset. (Contributed by Scott Fenton, 13-Mar-2025.) |
| ⊢ (𝜑 → 𝐴 ⊆ No ) & ⊢ (𝜑 → 𝐵 ⊆ 𝐴) ⇒ ⊢ (𝜑 → ∀𝑥 ∈ 𝐵 ∃𝑦 ∈ 𝐴 𝑦 ≤s 𝑥) | ||
| Theorem | cutlt 27840* | Eliminating all elements below a given element of a cut does not affect the cut. (Contributed by Scott Fenton, 13-Mar-2025.) |
| ⊢ (𝜑 → 𝐿 <<s 𝑅) & ⊢ (𝜑 → 𝐴 = (𝐿 |s 𝑅)) & ⊢ (𝜑 → 𝑋 ∈ 𝐿) ⇒ ⊢ (𝜑 → 𝐴 = (({𝑋} ∪ {𝑦 ∈ 𝐿 ∣ 𝑋 <s 𝑦}) |s 𝑅)) | ||
| Theorem | cutpos 27841* | Reduce the elements of a cut for a positive number. (Contributed by Scott Fenton, 13-Mar-2025.) |
| ⊢ (𝜑 → 𝐴 ∈ No ) & ⊢ (𝜑 → 0s <s 𝐴) ⇒ ⊢ (𝜑 → 𝐴 = (({ 0s } ∪ {𝑥 ∈ ( L ‘𝐴) ∣ 0s <s 𝑥}) |s ( R ‘𝐴))) | ||
| Theorem | cutmax 27842* | If 𝐴 has a maximum, then the maximum may be used alone in the cut. (Contributed by Scott Fenton, 20-Aug-2025.) |
| ⊢ (𝜑 → 𝐴 <<s 𝐵) & ⊢ (𝜑 → 𝑋 ∈ 𝐴) & ⊢ (𝜑 → ∀𝑦 ∈ 𝐴 𝑦 ≤s 𝑋) ⇒ ⊢ (𝜑 → (𝐴 |s 𝐵) = ({𝑋} |s 𝐵)) | ||
| Theorem | cutmin 27843* | If 𝐵 has a minimum, then the minimum may be used alone in the cut. (Contributed by Scott Fenton, 20-Aug-2025.) |
| ⊢ (𝜑 → 𝐴 <<s 𝐵) & ⊢ (𝜑 → 𝑋 ∈ 𝐵) & ⊢ (𝜑 → ∀𝑦 ∈ 𝐵 𝑋 ≤s 𝑦) ⇒ ⊢ (𝜑 → (𝐴 |s 𝐵) = (𝐴 |s {𝑋})) | ||
| Syntax | cnorec 27844 | Declare the syntax for surreal recursion of one variable. |
| class norec (𝐹) | ||
| Definition | df-norec 27845* | Define the recursion generator for surreal functions of one variable. This generator creates a recursive function of surreals from their value on their left and right sets. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ norec (𝐹) = frecs({⟨𝑥, 𝑦⟩ ∣ 𝑥 ∈ (( L ‘𝑦) ∪ ( R ‘𝑦))}, No , 𝐹) | ||
| Theorem | lrrecval 27846* | The next step in the development of the surreals is to establish induction and recursion across left and right sets. To that end, we are going to develop a relationship 𝑅 that is founded, partial, and set-like across the surreals. This first theorem just establishes the value of 𝑅. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝑅 = {⟨𝑥, 𝑦⟩ ∣ 𝑥 ∈ (( L ‘𝑦) ∪ ( R ‘𝑦))} ⇒ ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ) → (𝐴𝑅𝐵 ↔ 𝐴 ∈ (( L ‘𝐵) ∪ ( R ‘𝐵)))) | ||
| Theorem | lrrecval2 27847* | Next, we establish an alternate expression for 𝑅. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝑅 = {⟨𝑥, 𝑦⟩ ∣ 𝑥 ∈ (( L ‘𝑦) ∪ ( R ‘𝑦))} ⇒ ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ) → (𝐴𝑅𝐵 ↔ ( bday ‘𝐴) ∈ ( bday ‘𝐵))) | ||
| Theorem | lrrecpo 27848* | Now, we establish that 𝑅 is a partial ordering on No . (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝑅 = {⟨𝑥, 𝑦⟩ ∣ 𝑥 ∈ (( L ‘𝑦) ∪ ( R ‘𝑦))} ⇒ ⊢ 𝑅 Po No | ||
| Theorem | lrrecse 27849* | Next, we show that 𝑅 is set-like over No . (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝑅 = {⟨𝑥, 𝑦⟩ ∣ 𝑥 ∈ (( L ‘𝑦) ∪ ( R ‘𝑦))} ⇒ ⊢ 𝑅 Se No | ||
| Theorem | lrrecfr 27850* | Now we show that 𝑅 is founded over No . (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝑅 = {⟨𝑥, 𝑦⟩ ∣ 𝑥 ∈ (( L ‘𝑦) ∪ ( R ‘𝑦))} ⇒ ⊢ 𝑅 Fr No | ||
| Theorem | lrrecpred 27851* | Finally, we calculate the value of the predecessor class over 𝑅. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝑅 = {⟨𝑥, 𝑦⟩ ∣ 𝑥 ∈ (( L ‘𝑦) ∪ ( R ‘𝑦))} ⇒ ⊢ (𝐴 ∈ No → Pred(𝑅, No , 𝐴) = (( L ‘𝐴) ∪ ( R ‘𝐴))) | ||
| Theorem | noinds 27852* | Induction principle for a single surreal. If a property passes from a surreal's left and right sets to the surreal itself, then it holds for all surreals. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ (𝑥 = 𝑦 → (𝜑 ↔ 𝜓)) & ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜒)) & ⊢ (𝑥 ∈ No → (∀𝑦 ∈ (( L ‘𝑥) ∪ ( R ‘𝑥))𝜓 → 𝜑)) ⇒ ⊢ (𝐴 ∈ No → 𝜒) | ||
| Theorem | norecfn 27853 | Surreal recursion over one variable is a function over the surreals. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝐹 = norec (𝐺) ⇒ ⊢ 𝐹 Fn No | ||
| Theorem | norecov 27854 | Calculate the value of the surreal recursion operation. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝐹 = norec (𝐺) ⇒ ⊢ (𝐴 ∈ No → (𝐹‘𝐴) = (𝐴𝐺(𝐹 ↾ (( L ‘𝐴) ∪ ( R ‘𝐴))))) | ||
| Syntax | cnorec2 27855 | Declare the syntax for surreal recursion on two arguments. |
| class norec2 (𝐹) | ||
| Definition | df-norec2 27856* | Define surreal recursion on two variables. This function is key to the development of most of surreal numbers. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ norec2 (𝐹) = frecs({⟨𝑎, 𝑏⟩ ∣ (𝑎 ∈ ( No × No ) ∧ 𝑏 ∈ ( No × No ) ∧ (((1st ‘𝑎){⟨𝑐, 𝑑⟩ ∣ 𝑐 ∈ (( L ‘𝑑) ∪ ( R ‘𝑑))} (1st ‘𝑏) ∨ (1st ‘𝑎) = (1st ‘𝑏)) ∧ ((2nd ‘𝑎){⟨𝑐, 𝑑⟩ ∣ 𝑐 ∈ (( L ‘𝑑) ∪ ( R ‘𝑑))} (2nd ‘𝑏) ∨ (2nd ‘𝑎) = (2nd ‘𝑏)) ∧ 𝑎 ≠ 𝑏))}, ( No × No ), 𝐹) | ||
| Theorem | noxpordpo 27857* | To get through most of the textbook definitions in surreal numbers we will need recursion on two variables. This set of theorems sets up the preconditions for double recursion. This theorem establishes the partial ordering. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝑅 = {⟨𝑎, 𝑏⟩ ∣ 𝑎 ∈ (( L ‘𝑏) ∪ ( R ‘𝑏))} & ⊢ 𝑆 = {⟨𝑥, 𝑦⟩ ∣ (𝑥 ∈ ( No × No ) ∧ 𝑦 ∈ ( No × No ) ∧ (((1st ‘𝑥)𝑅(1st ‘𝑦) ∨ (1st ‘𝑥) = (1st ‘𝑦)) ∧ ((2nd ‘𝑥)𝑅(2nd ‘𝑦) ∨ (2nd ‘𝑥) = (2nd ‘𝑦)) ∧ 𝑥 ≠ 𝑦))} ⇒ ⊢ 𝑆 Po ( No × No ) | ||
| Theorem | noxpordfr 27858* | Next we establish the foundedness of the relationship. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝑅 = {⟨𝑎, 𝑏⟩ ∣ 𝑎 ∈ (( L ‘𝑏) ∪ ( R ‘𝑏))} & ⊢ 𝑆 = {⟨𝑥, 𝑦⟩ ∣ (𝑥 ∈ ( No × No ) ∧ 𝑦 ∈ ( No × No ) ∧ (((1st ‘𝑥)𝑅(1st ‘𝑦) ∨ (1st ‘𝑥) = (1st ‘𝑦)) ∧ ((2nd ‘𝑥)𝑅(2nd ‘𝑦) ∨ (2nd ‘𝑥) = (2nd ‘𝑦)) ∧ 𝑥 ≠ 𝑦))} ⇒ ⊢ 𝑆 Fr ( No × No ) | ||
| Theorem | noxpordse 27859* | Next we establish the set-like nature of the relationship. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝑅 = {⟨𝑎, 𝑏⟩ ∣ 𝑎 ∈ (( L ‘𝑏) ∪ ( R ‘𝑏))} & ⊢ 𝑆 = {⟨𝑥, 𝑦⟩ ∣ (𝑥 ∈ ( No × No ) ∧ 𝑦 ∈ ( No × No ) ∧ (((1st ‘𝑥)𝑅(1st ‘𝑦) ∨ (1st ‘𝑥) = (1st ‘𝑦)) ∧ ((2nd ‘𝑥)𝑅(2nd ‘𝑦) ∨ (2nd ‘𝑥) = (2nd ‘𝑦)) ∧ 𝑥 ≠ 𝑦))} ⇒ ⊢ 𝑆 Se ( No × No ) | ||
| Theorem | noxpordpred 27860* | Next we calculate the predecessor class of the relationship. (Contributed by Scott Fenton, 19-Aug-2024.) |
| ⊢ 𝑅 = {⟨𝑎, 𝑏⟩ ∣ 𝑎 ∈ (( L ‘𝑏) ∪ ( R ‘𝑏))} & ⊢ 𝑆 = {⟨𝑥, 𝑦⟩ ∣ (𝑥 ∈ ( No × No ) ∧ 𝑦 ∈ ( No × No ) ∧ (((1st ‘𝑥)𝑅(1st ‘𝑦) ∨ (1st ‘𝑥) = (1st ‘𝑦)) ∧ ((2nd ‘𝑥)𝑅(2nd ‘𝑦) ∨ (2nd ‘𝑥) = (2nd ‘𝑦)) ∧ 𝑥 ≠ 𝑦))} ⇒ ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ) → Pred(𝑆, ( No × No ), ⟨𝐴, 𝐵⟩) = ((((( L ‘𝐴) ∪ ( R ‘𝐴)) ∪ {𝐴}) × ((( L ‘𝐵) ∪ ( R ‘𝐵)) ∪ {𝐵})) ∖ {⟨𝐴, 𝐵⟩})) | ||
| Theorem | no2indslem 27861* | Double induction on surreals with explicit notation for the relationships. (Contributed by Scott Fenton, 22-Aug-2024.) |
| ⊢ 𝑅 = {⟨𝑎, 𝑏⟩ ∣ 𝑎 ∈ (( L ‘𝑏) ∪ ( R ‘𝑏))} & ⊢ (𝑥 = 𝑧 → (𝜑 ↔ 𝜓)) & ⊢ (𝑦 = 𝑤 → (𝜓 ↔ 𝜒)) & ⊢ (𝑥 = 𝑧 → (𝜃 ↔ 𝜒)) & ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜏)) & ⊢ (𝑦 = 𝐵 → (𝜏 ↔ 𝜂)) & ⊢ ((𝑥 ∈ No ∧ 𝑦 ∈ No ) → ((∀𝑧 ∈ (( L ‘𝑥) ∪ ( R ‘𝑥))∀𝑤 ∈ (( L ‘𝑦) ∪ ( R ‘𝑦))𝜒 ∧ ∀𝑧 ∈ (( L ‘𝑥) ∪ ( R ‘𝑥))𝜓 ∧ ∀𝑤 ∈ (( L ‘𝑦) ∪ ( R ‘𝑦))𝜃) → 𝜑)) ⇒ ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ) → 𝜂) | ||
| Theorem | no2inds 27862* | Double induction on surreals. The many substitution instances are to cover all possible cases. (Contributed by Scott Fenton, 22-Aug-2024.) |
| ⊢ (𝑥 = 𝑧 → (𝜑 ↔ 𝜓)) & ⊢ (𝑦 = 𝑤 → (𝜓 ↔ 𝜒)) & ⊢ (𝑥 = 𝑧 → (𝜃 ↔ 𝜒)) & ⊢ (𝑥 = 𝐴 → (𝜑 ↔ 𝜏)) & ⊢ (𝑦 = 𝐵 → (𝜏 ↔ 𝜂)) & ⊢ ((𝑥 ∈ No ∧ 𝑦 ∈ No ) → ((∀𝑧 ∈ (( L ‘𝑥) ∪ ( R ‘𝑥))∀𝑤 ∈ (( L ‘𝑦) ∪ ( R ‘𝑦))𝜒 ∧ ∀𝑧 ∈ (( L ‘𝑥) ∪ ( R ‘𝑥))𝜓 ∧ ∀𝑤 ∈ (( L ‘𝑦) ∪ ( R ‘𝑦))𝜃) → 𝜑)) ⇒ ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ) → 𝜂) | ||
| Theorem | norec2fn 27863 | The double-recursion operator on surreals yields a function on pairs of surreals. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ 𝐹 = norec2 (𝐺) ⇒ ⊢ 𝐹 Fn ( No × No ) | ||
| Theorem | norec2ov 27864 | The value of the double-recursion surreal function. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ 𝐹 = norec2 (𝐺) ⇒ ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ) → (𝐴𝐹𝐵) = (⟨𝐴, 𝐵⟩𝐺(𝐹 ↾ ((((( L ‘𝐴) ∪ ( R ‘𝐴)) ∪ {𝐴}) × ((( L ‘𝐵) ∪ ( R ‘𝐵)) ∪ {𝐵})) ∖ {⟨𝐴, 𝐵⟩})))) | ||
| Theorem | no3inds 27865* | Triple induction over surreal numbers. (Contributed by Scott Fenton, 9-Oct-2024.) |
| ⊢ (𝑎 = 𝑑 → (𝜑 ↔ 𝜓)) & ⊢ (𝑏 = 𝑒 → (𝜓 ↔ 𝜒)) & ⊢ (𝑐 = 𝑓 → (𝜒 ↔ 𝜃)) & ⊢ (𝑎 = 𝑑 → (𝜏 ↔ 𝜃)) & ⊢ (𝑏 = 𝑒 → (𝜂 ↔ 𝜏)) & ⊢ (𝑏 = 𝑒 → (𝜁 ↔ 𝜃)) & ⊢ (𝑐 = 𝑓 → (𝜎 ↔ 𝜏)) & ⊢ (𝑎 = 𝑋 → (𝜑 ↔ 𝜌)) & ⊢ (𝑏 = 𝑌 → (𝜌 ↔ 𝜇)) & ⊢ (𝑐 = 𝑍 → (𝜇 ↔ 𝜆)) & ⊢ ((𝑎 ∈ No ∧ 𝑏 ∈ No ∧ 𝑐 ∈ No ) → (((∀𝑑 ∈ (( L ‘𝑎) ∪ ( R ‘𝑎))∀𝑒 ∈ (( L ‘𝑏) ∪ ( R ‘𝑏))∀𝑓 ∈ (( L ‘𝑐) ∪ ( R ‘𝑐))𝜃 ∧ ∀𝑑 ∈ (( L ‘𝑎) ∪ ( R ‘𝑎))∀𝑒 ∈ (( L ‘𝑏) ∪ ( R ‘𝑏))𝜒 ∧ ∀𝑑 ∈ (( L ‘𝑎) ∪ ( R ‘𝑎))∀𝑓 ∈ (( L ‘𝑐) ∪ ( R ‘𝑐))𝜁) ∧ (∀𝑑 ∈ (( L ‘𝑎) ∪ ( R ‘𝑎))𝜓 ∧ ∀𝑒 ∈ (( L ‘𝑏) ∪ ( R ‘𝑏))∀𝑓 ∈ (( L ‘𝑐) ∪ ( R ‘𝑐))𝜏 ∧ ∀𝑒 ∈ (( L ‘𝑏) ∪ ( R ‘𝑏))𝜎) ∧ ∀𝑓 ∈ (( L ‘𝑐) ∪ ( R ‘𝑐))𝜂) → 𝜑)) ⇒ ⊢ ((𝑋 ∈ No ∧ 𝑌 ∈ No ∧ 𝑍 ∈ No ) → 𝜆) | ||
| Syntax | cadds 27866 | Declare the syntax for surreal addition. |
| class +s | ||
| Definition | df-adds 27867* | Define surreal addition. This is the first of the field operations on the surreals. Definition from [Conway] p. 5. Definition from [Gonshor] p. 13. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ +s = norec2 ((𝑥 ∈ V, 𝑎 ∈ V ↦ (({𝑦 ∣ ∃𝑙 ∈ ( L ‘(1st ‘𝑥))𝑦 = (𝑙𝑎(2nd ‘𝑥))} ∪ {𝑧 ∣ ∃𝑙 ∈ ( L ‘(2nd ‘𝑥))𝑧 = ((1st ‘𝑥)𝑎𝑙)}) |s ({𝑦 ∣ ∃𝑟 ∈ ( R ‘(1st ‘𝑥))𝑦 = (𝑟𝑎(2nd ‘𝑥))} ∪ {𝑧 ∣ ∃𝑟 ∈ ( R ‘(2nd ‘𝑥))𝑧 = ((1st ‘𝑥)𝑎𝑟)})))) | ||
| Theorem | addsfn 27868 | Surreal addition is a function over pairs of surreals. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ +s Fn ( No × No ) | ||
| Theorem | addsval 27869* | The value of surreal addition. Definition from [Conway] p. 5. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ) → (𝐴 +s 𝐵) = (({𝑦 ∣ ∃𝑙 ∈ ( L ‘𝐴)𝑦 = (𝑙 +s 𝐵)} ∪ {𝑧 ∣ ∃𝑙 ∈ ( L ‘𝐵)𝑧 = (𝐴 +s 𝑙)}) |s ({𝑦 ∣ ∃𝑟 ∈ ( R ‘𝐴)𝑦 = (𝑟 +s 𝐵)} ∪ {𝑧 ∣ ∃𝑟 ∈ ( R ‘𝐵)𝑧 = (𝐴 +s 𝑟)}))) | ||
| Theorem | addsval2 27870* | The value of surreal addition with different choices for each bound variable. Definition from [Conway] p. 5. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ) → (𝐴 +s 𝐵) = (({𝑦 ∣ ∃𝑙 ∈ ( L ‘𝐴)𝑦 = (𝑙 +s 𝐵)} ∪ {𝑧 ∣ ∃𝑚 ∈ ( L ‘𝐵)𝑧 = (𝐴 +s 𝑚)}) |s ({𝑤 ∣ ∃𝑟 ∈ ( R ‘𝐴)𝑤 = (𝑟 +s 𝐵)} ∪ {𝑡 ∣ ∃𝑠 ∈ ( R ‘𝐵)𝑡 = (𝐴 +s 𝑠)}))) | ||
| Theorem | addsrid 27871 | Surreal addition to zero is identity. Part of Theorem 3 of [Conway] p. 17. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ (𝐴 ∈ No → (𝐴 +s 0s ) = 𝐴) | ||
| Theorem | addsridd 27872 | Surreal addition to zero is identity. Part of Theorem 3 of [Conway] p. 17. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ No ) ⇒ ⊢ (𝜑 → (𝐴 +s 0s ) = 𝐴) | ||
| Theorem | addscom 27873 | Surreal addition commutes. Part of Theorem 3 of [Conway] p. 17. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ) → (𝐴 +s 𝐵) = (𝐵 +s 𝐴)) | ||
| Theorem | addscomd 27874 | Surreal addition commutes. Part of Theorem 3 of [Conway] p. 17. (Contributed by Scott Fenton, 20-Aug-2024.) |
| ⊢ (𝜑 → 𝐴 ∈ No ) & ⊢ (𝜑 → 𝐵 ∈ No ) ⇒ ⊢ (𝜑 → (𝐴 +s 𝐵) = (𝐵 +s 𝐴)) | ||
| Theorem | addslid 27875 | Surreal addition to zero is identity. (Contributed by Scott Fenton, 3-Feb-2025.) |
| ⊢ (𝐴 ∈ No → ( 0s +s 𝐴) = 𝐴) | ||
| Theorem | addsproplem1 27876* | Lemma for surreal addition properties. To prove closure on surreal addition we need to prove that addition is compatible with order at the same time. We do this by inducting over the maximum of two natural sums of the birthdays of surreals numbers. In the final step we will loop around and use tfr3 8367 to prove this of all surreals. This first lemma just instantiates the inductive hypothesis so we do not need to do it continuously throughout the proof. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ (𝜑 → ∀𝑥 ∈ No ∀𝑦 ∈ No ∀𝑧 ∈ No (((( bday ‘𝑥) +no ( bday ‘𝑦)) ∪ (( bday ‘𝑥) +no ( bday ‘𝑧))) ∈ ((( bday ‘𝑋) +no ( bday ‘𝑌)) ∪ (( bday ‘𝑋) +no ( bday ‘𝑍))) → ((𝑥 +s 𝑦) ∈ No ∧ (𝑦 <s 𝑧 → (𝑦 +s 𝑥) <s (𝑧 +s 𝑥))))) & ⊢ (𝜑 → 𝐴 ∈ No ) & ⊢ (𝜑 → 𝐵 ∈ No ) & ⊢ (𝜑 → 𝐶 ∈ No ) & ⊢ (𝜑 → ((( bday ‘𝐴) +no ( bday ‘𝐵)) ∪ (( bday ‘𝐴) +no ( bday ‘𝐶))) ∈ ((( bday ‘𝑋) +no ( bday ‘𝑌)) ∪ (( bday ‘𝑋) +no ( bday ‘𝑍)))) ⇒ ⊢ (𝜑 → ((𝐴 +s 𝐵) ∈ No ∧ (𝐵 <s 𝐶 → (𝐵 +s 𝐴) <s (𝐶 +s 𝐴)))) | ||
| Theorem | addsproplem2 27877* | Lemma for surreal addition properties. When proving closure for operations defined using norec and norec2, it is a strictly stronger statement to say that the cut defined is actually a cut than it is to say that the operation is closed. We will often prove this stronger statement. Here, we do so for the cut involved in surreal addition. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ (𝜑 → ∀𝑥 ∈ No ∀𝑦 ∈ No ∀𝑧 ∈ No (((( bday ‘𝑥) +no ( bday ‘𝑦)) ∪ (( bday ‘𝑥) +no ( bday ‘𝑧))) ∈ ((( bday ‘𝑋) +no ( bday ‘𝑌)) ∪ (( bday ‘𝑋) +no ( bday ‘𝑍))) → ((𝑥 +s 𝑦) ∈ No ∧ (𝑦 <s 𝑧 → (𝑦 +s 𝑥) <s (𝑧 +s 𝑥))))) & ⊢ (𝜑 → 𝑋 ∈ No ) & ⊢ (𝜑 → 𝑌 ∈ No ) ⇒ ⊢ (𝜑 → ({𝑝 ∣ ∃𝑙 ∈ ( L ‘𝑋)𝑝 = (𝑙 +s 𝑌)} ∪ {𝑞 ∣ ∃𝑚 ∈ ( L ‘𝑌)𝑞 = (𝑋 +s 𝑚)}) <<s ({𝑤 ∣ ∃𝑟 ∈ ( R ‘𝑋)𝑤 = (𝑟 +s 𝑌)} ∪ {𝑡 ∣ ∃𝑠 ∈ ( R ‘𝑌)𝑡 = (𝑋 +s 𝑠)})) | ||
| Theorem | addsproplem3 27878* | Lemma for surreal addition properties. Show the cut properties of surreal addition. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ (𝜑 → ∀𝑥 ∈ No ∀𝑦 ∈ No ∀𝑧 ∈ No (((( bday ‘𝑥) +no ( bday ‘𝑦)) ∪ (( bday ‘𝑥) +no ( bday ‘𝑧))) ∈ ((( bday ‘𝑋) +no ( bday ‘𝑌)) ∪ (( bday ‘𝑋) +no ( bday ‘𝑍))) → ((𝑥 +s 𝑦) ∈ No ∧ (𝑦 <s 𝑧 → (𝑦 +s 𝑥) <s (𝑧 +s 𝑥))))) & ⊢ (𝜑 → 𝑋 ∈ No ) & ⊢ (𝜑 → 𝑌 ∈ No ) ⇒ ⊢ (𝜑 → ((𝑋 +s 𝑌) ∈ No ∧ ({𝑝 ∣ ∃𝑙 ∈ ( L ‘𝑋)𝑝 = (𝑙 +s 𝑌)} ∪ {𝑞 ∣ ∃𝑚 ∈ ( L ‘𝑌)𝑞 = (𝑋 +s 𝑚)}) <<s {(𝑋 +s 𝑌)} ∧ {(𝑋 +s 𝑌)} <<s ({𝑤 ∣ ∃𝑟 ∈ ( R ‘𝑋)𝑤 = (𝑟 +s 𝑌)} ∪ {𝑡 ∣ ∃𝑠 ∈ ( R ‘𝑌)𝑡 = (𝑋 +s 𝑠)}))) | ||
| Theorem | addsproplem4 27879* | Lemma for surreal addition properties. Show the second half of the inductive hypothesis when 𝑌 is older than 𝑍. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ (𝜑 → ∀𝑥 ∈ No ∀𝑦 ∈ No ∀𝑧 ∈ No (((( bday ‘𝑥) +no ( bday ‘𝑦)) ∪ (( bday ‘𝑥) +no ( bday ‘𝑧))) ∈ ((( bday ‘𝑋) +no ( bday ‘𝑌)) ∪ (( bday ‘𝑋) +no ( bday ‘𝑍))) → ((𝑥 +s 𝑦) ∈ No ∧ (𝑦 <s 𝑧 → (𝑦 +s 𝑥) <s (𝑧 +s 𝑥))))) & ⊢ (𝜑 → 𝑋 ∈ No ) & ⊢ (𝜑 → 𝑌 ∈ No ) & ⊢ (𝜑 → 𝑍 ∈ No ) & ⊢ (𝜑 → 𝑌 <s 𝑍) & ⊢ (𝜑 → ( bday ‘𝑌) ∈ ( bday ‘𝑍)) ⇒ ⊢ (𝜑 → (𝑌 +s 𝑋) <s (𝑍 +s 𝑋)) | ||
| Theorem | addsproplem5 27880* | Lemma for surreal addition properties. Show the second half of the inductive hypothesis when 𝑍 is older than 𝑌. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ (𝜑 → ∀𝑥 ∈ No ∀𝑦 ∈ No ∀𝑧 ∈ No (((( bday ‘𝑥) +no ( bday ‘𝑦)) ∪ (( bday ‘𝑥) +no ( bday ‘𝑧))) ∈ ((( bday ‘𝑋) +no ( bday ‘𝑌)) ∪ (( bday ‘𝑋) +no ( bday ‘𝑍))) → ((𝑥 +s 𝑦) ∈ No ∧ (𝑦 <s 𝑧 → (𝑦 +s 𝑥) <s (𝑧 +s 𝑥))))) & ⊢ (𝜑 → 𝑋 ∈ No ) & ⊢ (𝜑 → 𝑌 ∈ No ) & ⊢ (𝜑 → 𝑍 ∈ No ) & ⊢ (𝜑 → 𝑌 <s 𝑍) & ⊢ (𝜑 → ( bday ‘𝑍) ∈ ( bday ‘𝑌)) ⇒ ⊢ (𝜑 → (𝑌 +s 𝑋) <s (𝑍 +s 𝑋)) | ||
| Theorem | addsproplem6 27881* | Lemma for surreal addition properties. Finally, we show the second half of the induction hypothesis when 𝑌 and 𝑍 are the same age. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ (𝜑 → ∀𝑥 ∈ No ∀𝑦 ∈ No ∀𝑧 ∈ No (((( bday ‘𝑥) +no ( bday ‘𝑦)) ∪ (( bday ‘𝑥) +no ( bday ‘𝑧))) ∈ ((( bday ‘𝑋) +no ( bday ‘𝑌)) ∪ (( bday ‘𝑋) +no ( bday ‘𝑍))) → ((𝑥 +s 𝑦) ∈ No ∧ (𝑦 <s 𝑧 → (𝑦 +s 𝑥) <s (𝑧 +s 𝑥))))) & ⊢ (𝜑 → 𝑋 ∈ No ) & ⊢ (𝜑 → 𝑌 ∈ No ) & ⊢ (𝜑 → 𝑍 ∈ No ) & ⊢ (𝜑 → 𝑌 <s 𝑍) & ⊢ (𝜑 → ( bday ‘𝑌) = ( bday ‘𝑍)) ⇒ ⊢ (𝜑 → (𝑌 +s 𝑋) <s (𝑍 +s 𝑋)) | ||
| Theorem | addsproplem7 27882* | Lemma for surreal addition properties. Putting together the three previous lemmas, we now show the second half of the inductive hypothesis unconditionally. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ (𝜑 → ∀𝑥 ∈ No ∀𝑦 ∈ No ∀𝑧 ∈ No (((( bday ‘𝑥) +no ( bday ‘𝑦)) ∪ (( bday ‘𝑥) +no ( bday ‘𝑧))) ∈ ((( bday ‘𝑋) +no ( bday ‘𝑌)) ∪ (( bday ‘𝑋) +no ( bday ‘𝑍))) → ((𝑥 +s 𝑦) ∈ No ∧ (𝑦 <s 𝑧 → (𝑦 +s 𝑥) <s (𝑧 +s 𝑥))))) & ⊢ (𝜑 → 𝑋 ∈ No ) & ⊢ (𝜑 → 𝑌 ∈ No ) & ⊢ (𝜑 → 𝑍 ∈ No ) & ⊢ (𝜑 → 𝑌 <s 𝑍) ⇒ ⊢ (𝜑 → (𝑌 +s 𝑋) <s (𝑍 +s 𝑋)) | ||
| Theorem | addsprop 27883 | Inductively show that surreal addition is closed and compatible with less-than. This proof follows from induction on the birthdays of the surreal numbers involved. This pattern occurs throughout surreal development. Theorem 3.1 of [Gonshor] p. 14. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝑋 ∈ No ∧ 𝑌 ∈ No ∧ 𝑍 ∈ No ) → ((𝑋 +s 𝑌) ∈ No ∧ (𝑌 <s 𝑍 → (𝑌 +s 𝑋) <s (𝑍 +s 𝑋)))) | ||
| Theorem | addscutlem 27884* | Lemma for addscut 27885. Show the statement with some additional distinct variable conditions. (Contributed by Scott Fenton, 8-Mar-2025.) |
| ⊢ (𝜑 → 𝑋 ∈ No ) & ⊢ (𝜑 → 𝑌 ∈ No ) ⇒ ⊢ (𝜑 → ((𝑋 +s 𝑌) ∈ No ∧ ({𝑝 ∣ ∃𝑙 ∈ ( L ‘𝑋)𝑝 = (𝑙 +s 𝑌)} ∪ {𝑞 ∣ ∃𝑚 ∈ ( L ‘𝑌)𝑞 = (𝑋 +s 𝑚)}) <<s {(𝑋 +s 𝑌)} ∧ {(𝑋 +s 𝑌)} <<s ({𝑤 ∣ ∃𝑟 ∈ ( R ‘𝑋)𝑤 = (𝑟 +s 𝑌)} ∪ {𝑡 ∣ ∃𝑠 ∈ ( R ‘𝑌)𝑡 = (𝑋 +s 𝑠)}))) | ||
| Theorem | addscut 27885* | Demonstrate the cut properties of surreal addition. This gives us closure together with a pair of set-less-than relationships for surreal addition. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ (𝜑 → 𝑋 ∈ No ) & ⊢ (𝜑 → 𝑌 ∈ No ) ⇒ ⊢ (𝜑 → ((𝑋 +s 𝑌) ∈ No ∧ ({𝑝 ∣ ∃𝑙 ∈ ( L ‘𝑋)𝑝 = (𝑙 +s 𝑌)} ∪ {𝑞 ∣ ∃𝑚 ∈ ( L ‘𝑌)𝑞 = (𝑋 +s 𝑚)}) <<s {(𝑋 +s 𝑌)} ∧ {(𝑋 +s 𝑌)} <<s ({𝑤 ∣ ∃𝑟 ∈ ( R ‘𝑋)𝑤 = (𝑟 +s 𝑌)} ∪ {𝑡 ∣ ∃𝑠 ∈ ( R ‘𝑌)𝑡 = (𝑋 +s 𝑠)}))) | ||
| Theorem | addscut2 27886* | Show that the cut involved in surreal addition is legitimate. (Contributed by Scott Fenton, 8-Mar-2025.) |
| ⊢ (𝜑 → 𝑋 ∈ No ) & ⊢ (𝜑 → 𝑌 ∈ No ) ⇒ ⊢ (𝜑 → ({𝑝 ∣ ∃𝑙 ∈ ( L ‘𝑋)𝑝 = (𝑙 +s 𝑌)} ∪ {𝑞 ∣ ∃𝑚 ∈ ( L ‘𝑌)𝑞 = (𝑋 +s 𝑚)}) <<s ({𝑤 ∣ ∃𝑟 ∈ ( R ‘𝑋)𝑤 = (𝑟 +s 𝑌)} ∪ {𝑡 ∣ ∃𝑠 ∈ ( R ‘𝑌)𝑡 = (𝑋 +s 𝑠)})) | ||
| Theorem | addscld 27887 | Surreal numbers are closed under addition. Theorem 6(iii) of [Conway] p. 18. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ (𝜑 → 𝑋 ∈ No ) & ⊢ (𝜑 → 𝑌 ∈ No ) ⇒ ⊢ (𝜑 → (𝑋 +s 𝑌) ∈ No ) | ||
| Theorem | addscl 27888 | Surreal numbers are closed under addition. Theorem 6(iii) of [Conway[ p. 18. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ) → (𝐴 +s 𝐵) ∈ No ) | ||
| Theorem | addsf 27889 | Function statement for surreal addition. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ +s :( No × No )⟶ No | ||
| Theorem | addsfo 27890 | Surreal addition is onto. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ +s :( No × No )–onto→ No | ||
| Theorem | peano2no 27891 | A theorem for surreals that is analogous to the second Peano postulate peano2 7866. (Contributed by Scott Fenton, 17-Mar-2025.) |
| ⊢ (𝐴 ∈ No → (𝐴 +s 1s ) ∈ No ) | ||
| Theorem | sltadd1im 27892 | Surreal less-than is preserved under addition. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ∧ 𝐶 ∈ No ) → (𝐴 <s 𝐵 → (𝐴 +s 𝐶) <s (𝐵 +s 𝐶))) | ||
| Theorem | sltadd2im 27893 | Surreal less-than is preserved under addition. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ∧ 𝐶 ∈ No ) → (𝐴 <s 𝐵 → (𝐶 +s 𝐴) <s (𝐶 +s 𝐵))) | ||
| Theorem | sleadd1im 27894 | Surreal less-than or equal cancels under addition. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ∧ 𝐶 ∈ No ) → ((𝐴 +s 𝐶) ≤s (𝐵 +s 𝐶) → 𝐴 ≤s 𝐵)) | ||
| Theorem | sleadd2im 27895 | Surreal less-than or equal cancels under addition. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ∧ 𝐶 ∈ No ) → ((𝐶 +s 𝐴) ≤s (𝐶 +s 𝐵) → 𝐴 ≤s 𝐵)) | ||
| Theorem | sleadd1 27896 | Addition to both sides of surreal less-than or equal. Theorem 5 of [Conway] p. 18. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ∧ 𝐶 ∈ No ) → (𝐴 ≤s 𝐵 ↔ (𝐴 +s 𝐶) ≤s (𝐵 +s 𝐶))) | ||
| Theorem | sleadd2 27897 | Addition to both sides of surreal less-than or equal. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ∧ 𝐶 ∈ No ) → (𝐴 ≤s 𝐵 ↔ (𝐶 +s 𝐴) ≤s (𝐶 +s 𝐵))) | ||
| Theorem | sltadd2 27898 | Addition to both sides of surreal less-than. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ∧ 𝐶 ∈ No ) → (𝐴 <s 𝐵 ↔ (𝐶 +s 𝐴) <s (𝐶 +s 𝐵))) | ||
| Theorem | sltadd1 27899 | Addition to both sides of surreal less-than. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ∧ 𝐶 ∈ No ) → (𝐴 <s 𝐵 ↔ (𝐴 +s 𝐶) <s (𝐵 +s 𝐶))) | ||
| Theorem | addscan2 27900 | Cancellation law for surreal addition. (Contributed by Scott Fenton, 21-Jan-2025.) |
| ⊢ ((𝐴 ∈ No ∧ 𝐵 ∈ No ∧ 𝐶 ∈ No ) → ((𝐴 +s 𝐶) = (𝐵 +s 𝐶) ↔ 𝐴 = 𝐵)) | ||
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