This PR introduces a function `String.split` which is based on
`String.Slice.split` and therefore supports all pattern types and
returns a `Std.Iter String.Slice`.
This supersedes the functions `String.splitOn` and `String.splitToList`,
and we remove all all uses of these functions from core. They will be
deprecated in a future PR.
Migrating from `String.splitOn` and `String.splitToList` is easy: we
introduce functions `Iter.toStringList` and `Iter.toStringArray` that
can be used to conveniently go from `Std.Iter String.Slice` to `List
String` and `Array String`, so for example `s.splitOn "foo"` can be
replaced by `s.split "foo" |>.toStringList`.
This PR defines `String.Slice.replace` and redefines `String.replace` to
use the `Slice` version.
The new implementation is generic in the pattern, so it supports things
like `"education".replace isVowel "☃!" = "☃!d☃!c☃!t☃!☃!n"`. Since it
uses the `ForwardSearcher` infrastructure, `String` patterns are
searched using KMP, unlike the previous implementation which had
quadratic runtime. As a side effect, the behavior when replacing an
empty string now matches that of most other programming languages,
namely `"abc".replace "" "k" = "kakbkck"`.
This PR adds a `bootstrap` option to Lake which is used to identify the
core Lean package. This enables Lake to use the current stage's include
directory rather than the Lean toolchains when compiling Lean with Lean
in core.
**Breaking change:** The Lean library directory is no longer part of
`getLeanLinkSharedFlags`. FFI users should provide this option
separately when linking to Lean (e.g.. via `s!"-L{(←
getLeanLibDir).toString}"`). See the FFI example for a demonstration.
