Commit graph

3 commits

Author SHA1 Message Date
Leonardo de Moura
08718e33dc refactor(builtin): only load the kernel and natural numbers by default
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-12-30 13:35:37 -08:00
Leonardo de Moura
4dd6cead83 refactor(equality): make homogeneous equality the default equality
It was not a good idea to use heterogeneous equality as the default equality in Lean.
It creates the following problems.

- Heterogeneous equality does not propagate constraints in the elaborator.
For example, suppose that l has type (List Int), then the expression
     l = nil
will not propagate the type (List Int) to nil.

- It is easy to write false. For example, suppose x has type Real, and the user
writes x = 0. This is equivalent to false, since 0 has type Nat. The elaborator cannot introduce
the coercion since x = 0 is a type correct expression.

Homogeneous equality does not suffer from the problems above.
We keep heterogeneous equality because it is useful for generating proof terms.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-10-29 16:20:06 -07:00
Leonardo de Moura
3992c4b8f9 Define divides, and add examples
Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
2013-09-03 20:18:20 -07:00