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| -rw-r--r-- | doc/rust.md | 21 |
1 files changed, 4 insertions, 17 deletions
diff --git a/doc/rust.md b/doc/rust.md index 3c6157e44ba..730f78ea082 100644 --- a/doc/rust.md +++ b/doc/rust.md @@ -2459,25 +2459,12 @@ do k(3) |j| { ### For expressions ~~~~~~~~{.ebnf .gram} -for_expr : "for" expr [ '|' ident_list '|' ] ? '{' block '}' ; +for_expr : "for" pat "in" expr '{' block '}' ; ~~~~~~~~ -A _for expression_ is similar to a [`do` expression](#do-expressions), -in that it provides a special block-form of lambda expression, -suited to passing the `block` function to a higher-order function implementing a loop. - -In contrast to a `do` expression, a `for` expression is designed to work -with methods such as `each` and `times`, that require the body block to -return a boolean. The `for` expression accommodates this by implicitly -returning `true` at the end of each block, unless a `break` expression -is evaluated. - -In addition, [`break`](#break-expressions) and [`loop`](#loop-expressions) expressions -are rewritten inside `for` expressions in the same way that `return` expressions are, -with a combination of local flag variables, -and early boolean-valued returns from the `block` function, -such that the meaning of `break` and `loop` is preserved in a primitive loop -when rewritten as a `for` loop controlled by a higher order function. +A `for` expression is a syntactic construct for looping +over elements provided by an implementation of +`std::iterator::Iterator`. An example of a for loop over the contents of a vector: |