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| -rw-r--r-- | src/doc/unstable-book/src/language-features/macro-at-most-once-rep.md | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/src/doc/unstable-book/src/language-features/macro-at-most-once-rep.md b/src/doc/unstable-book/src/language-features/macro-at-most-once-rep.md new file mode 100644 index 00000000000..dbaf91b6e78 --- /dev/null +++ b/src/doc/unstable-book/src/language-features/macro-at-most-once-rep.md @@ -0,0 +1,17 @@ +# `macro_at_most_once_rep` + +The tracking issue for this feature is: TODO(mark-i-m) + +With this feature gate enabled, one can use `?` as a Kleene operator meaning "0 +or 1 repetitions" in a macro definition. Previously only `+` and `*` were allowed. + +For example: +```rust +macro_rules! foo { + (something $(,)?) // `?` indicates `,` is "optional"... + => {} +} +``` + +------------------------ + |