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Gödel numbering of natural deduction derivations using =Intro Inc fixes#419

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rzach merged 3 commits intoOpenLogicProject:masterfrom
beastaugh:inc-fixes
Feb 15, 2026
Merged

Gödel numbering of natural deduction derivations using =Intro Inc fixes#419
rzach merged 3 commits intoOpenLogicProject:masterfrom
beastaugh:inc-fixes

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Resolves #417.

As written, a discharge of the assumption by the final inference (0)
would be ignored. This commit fixes that.
As written it checks for identity between s_i and s_j, two indexes
of elements of the same sequence s, rather than indexes of elements
of two distinct sequences s and s'. This commit fixes that.
This sets their value to <0,e,n,k> where e is the Gödel number of
an equation of the form t=t, n=0 is the discharge label, and k=15.

This resolves an issue where it wasn't clear what Gödel number
applications of =Intro should have, since Gödel numbers of
applications of rules were defined only for rules with non-zero
numbers of premises, while a later proof assumed that the rule
had one premise which was the empty derivation tree <>.
@rzach rzach merged commit c6b2151 into OpenLogicProject:master Feb 15, 2026
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Gödel numbering of natural deduction derivations using =Intro

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