@aqjune @nunoplopes: See new tests at tests/lean/run/random.lean
We have two actions in `io`. By default, `io` uses the C++
random number generator, but we can force it to use a `std_gen` with
the action `set_rand_gen`.
def rand (lo : nat := std_range.1) (hi : nat := std_range.2) : io nat
def set_rand_gen : std_gen → io unit
@aqjune @nunoplopes: This commit adds basic support for random numbers.
It defines a random number generator interface, and an basic
implementation based on the Haskell one.
We can add more implementations in the future if neeeded.
The new test program has a few examples.
BTW, this is a pure Lean implementation.
If we need more performance we can provide an implementation
using C++.
The theorems themselves are unchanged, although the proofs had to be reordered and changed a bit to accomodate.
Conflicts:
library/init/algebra/ordered_field.lean
The previous `decidable_bex` was using a nasty hack.
First, it was relying on a bug in the local_context object that was
fixed at commit 6060b75e6. Note that, the type class resolution
will be even more restrictive after we implement the fix described at a75b0d8ee.
Second, it was built using tactics that are meant for constructing
proof irrelevant code (e.g., `simp`).
We also document the problem to make sure we don't spend time again
trying to understand the workaround. This is an instance of a bigger
problem that should be addressed later.
- An new simp attribute may depend on other existing attributes
- Add `[norm]` simp attribute. It is an extension of the default `[simp]` attribute.
It should be used to add extra rules for normalizing goals.
These extra rules are used to produce normal forms and/or reduce the
number of constants used in a goal. Here is an example coming from a
discussion with @kha. When working with monads, we may want to
eliminate `<$>` by using the lemma `f <$> x = x >>= pure ∘ f`.
This lemma is in the `[norm]` simp set, but it is not in `[simp]`
@kha I've added
iterator.extract : iterator -> iterator -> option string
It returns `none` if the iterators are "incompatible".
If this function is inconvenient to use, we can change it and return the
empty string in these cases.
Given iterators `it1` and `it2`, if they are sharing the same string
object in memory, then the cost is O(pos(it2) - pos(it1)).
If not, we have an extra O(N) step where we check whether the strings
being iterated by it1 and it2 are equal (`N` is the size of the strings).
In most applications, I believe the iterators will share the string
object.
I didn't test the code much. BTW, I found an unrelated bug at
vm_string.cpp. So, I'm not very confident this code is rock solid.
This command is not just a cosmetic feature.
We need it to defined `id_rhs` before the tactic framework is defined.
We want `id_rhs` to be used in all definitions generated by the equation
compiler. Right now, it is only used in definitions defined after the
tactic framework.
