Summary:
Change the type of `fold` functions to enable them to compose
better. The guiding reasoning behind using types such as:
```
val fold : 'a t -> 's -> f:('a -> 's -> 's) -> 's
```
is:
1. The function argument should be labeled. This is so that it can be
reordered relative to the others, since it is often a multi-line
`fun` expression.
2. The function argument should come last. This enables its
arguments (which are often polymorphic) to benefit from type-based
disambiguation information determined by the types of the other
arguments at the call sites.
3. The function argument's type should produce an
accumulator-transformer when partially-applied. That is,
`f x : 's -> 's`. This composes well with other functions designed
to produce transformers/endofunctions when partially applied, and
in particular improves the common case of composing folds into
"state-passing style" code.
4. The fold function itself should produce an accumulator-transformer
when partially applied. So `'a t -> 's -> f:_ -> 's` rather than
`'s -> 'a t -> f:_ -> 's` or `'a t -> init:'s -> f:_ -> 's` etc.
Reviewed By: jvillard
Differential Revision: D24306063
fbshipit-source-id: 13bd8bbee
Summary:
Expressing the sort of short-circuit evaluation in the changed code is
conceptually more direct using iterators.
Also, when using With_return, getting usable backtraces relies on the
compiler recognizing that the `raise` in the implementation of
`Base.Exn.raise_without_backtrace` should be a `reraise`. Using
iterators avoids this potential fragility.
Reviewed By: jvillard
Differential Revision: D24306094
fbshipit-source-id: b1abe04fb
Summary:
The treatment of comparison and exceptions in Core/Core_kernel/Base
makes them questionable as the default. This diff changes nonstdlib so
that Core is no longer opened in the global namespace, and makes a few
changes to handle the resulting minor API changes. This leads to a
lighter-touch nonstdlib, which makes a few definitions of its own, and
selects and extends modules from several libraries, including base,
core_kernel, containers, iter.
Reviewed By: jvillard
Differential Revision: D24306090
fbshipit-source-id: 42c91bd1b
Summary:
Currently the symbolic execution code in `Exec` manually threads
universal and existential variable contexts through virtually every
function. It is easy to mistakenly pass on a context that is not the
latest-extended one, or to forget to add generated variables to the
contexts.
This patch adds a state monad, `Fresh`, to manage the generation of
fresh variables in `Exec`. This is a standard state monad where the
state is two sets of variables: those to which fresh variables must be
chosen fresh, and those which have been generated. This yields an
abstraction where an `'a Fresh.t` value represents a value of type
`'a` which may contain as-yet-unnamed variables, and `Fresh.gen ~wrt
a` generates names that are fresh with respect to `wrt` for all
unnamed variables in `a`, and yields the set of generated variables
together with `a` expressed in terms of those variables.
Reviewed By: jvillard
Differential Revision: D21974018
fbshipit-source-id: 1917e82c0
Josh Berdine