Questions tagged [definition]

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2 votes
1 answer
72 views

How do clausal definitions work?

I'm most familiar with the metatheory of calculi based around expressions. But systems like Agda use separate clauses for definitions. ...
5 votes
2 answers
157 views

Unclarity about Preorder class in Lean4

I realize the port of Mathlib to Lean4 is not finished yet, but I've run into a definition that I do not quite understand. I'm quite new at using theoremprovers as well as stackexchange, so please be ...
1 vote
1 answer
57 views

Question about default definitions in fields

In Unclarity about Preorder class in Lean4 I asked why the third and fourth field (lt and lt_iff_le_not_le) in the definition of MyPreorder below would both be necessary, as one follows from the other ...
0 votes
1 answer
64 views

Define a function using another function

I want to define a translation function g from another function f. Definition trans (f g : Q -> Q) (t : Q) := forall q : Q, f (q + t) == g q. In the above code,...
5 votes
0 answers
198 views

An algorithm for the substitution of formulas for predicates in first order logic

I am trying to find a detailed description of the definition of substitution of formulas for predicates in first order logic and an implementation of this as a function in Lean or Haskell. The aim is ...
3 votes
2 answers
179 views

Coq defining a hierarchy of collections of integers with infinitely many "levels"

I'm trying to formalize a small part of higher-order arithmetic in Coq as an exercise (Wikipedia article for second-order arithmetic). It's straightforward to formalize something resembling second-...