Questions tagged [type-checking]

Checking that types adhere to the tying rules.

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2 votes
1 answer
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Why does an internal term produced by Lean's equation compiler have holes in it?

Section 4.7 of the Lean reference manual (version 3.3) gives an example of a division function defined by well-founded recursion. I used the #print command to ...
ttbo's user avatar
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1 vote
1 answer
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Code obtained from printing a definition from the Lean 3.46 equation compiler does not type check. Why doesn't it, and how can I fix it?

In the example below, the fibonacci function is defined via the Lean equation compiler. However, there seems to be a problem with the code that is obtained from running ...
ttbo's user avatar
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6 votes
1 answer
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How do I convince the Lean 4 type checker that addition is commutative?

In order to get acquainted with Lean and programming with dependent types I am trying to implement basic operations for a Vector datatype defined following the ...
BackusNaur's user avatar
6 votes
1 answer
113 views

Does Coq's Module and Functor type-check incrementally?

I am trying to search the following questions online but I failed: When applying a functor (parametrized module), will the contents inside the functor be re-type-checked? Will Coq's command ...
Ende Jin's user avatar
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16 votes
2 answers
2k views

What is bidirectional type checking?

What is bidirectional type checking and why would I want to implement it? It feels like the name is a bit of a misnomer and the syntactic separation kind of resembles stuff like ANF, call by push ...
Molossus Spondee's user avatar
9 votes
1 answer
265 views

Type Checking Undecidable in Extensional Type Theory

What is the difference between intensional vs extensional type theories and how come the type checking is undecidable for extensional type theory? Also, how does it affect the expressiveness of ...
keep_learning's user avatar
11 votes
1 answer
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In the "Simply Easy!" paper, why is it safe to evaluate types in the empty environment?

The paper in question: An Implementation of a Dependently Typed Lambda Calculus by Andres Löh, Conor McBride and Wouter Swierstra. I'm wondering whether it's correct in what's it is doing. Precisely ...
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