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Diffstat (limited to 'runtime/doc/eval.txt')
| -rw-r--r-- | runtime/doc/eval.txt | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt index 62ee26cf54..fb4ca824a3 100644 --- a/runtime/doc/eval.txt +++ b/runtime/doc/eval.txt @@ -1186,7 +1186,7 @@ the following ways: 1. The body of the lambda expression is an |expr1| and not a sequence of |Ex| commands. -2. The prefix "a:" is optional for arguments. E.g.: > +2. The prefix "a:" should not be used for arguments. E.g.: > :let F = {arg1, arg2 -> arg1 - arg2} :echo F(5, 2) < 3 @@ -1195,6 +1195,18 @@ The arguments are optional. Example: > :let F = {-> 'error function'} :echo F() < error function + *closure* +Lambda expressions can access outer scope variables and arguments. This is +often called a closure. Example where "i" a and "a:arg" are used in a lambda +while they exists in the function scope. They remain valid even after the +function returns: > + :function Foo(arg) + : let i = 3 + : return {x -> x + i - a:arg} + :endfunction + :let Bar = Foo(4) + :echo Bar(6) +< 5 Examples for using a lambda expression with |sort()|, |map()| and |filter()|: > :echo map([1, 2, 3], {idx, val -> val + 1}) @@ -1212,6 +1224,12 @@ The lambda expression is also useful for Channel, Job and timer: > Note how execute() is used to execute an Ex command. That's ugly though. + +Lambda expressions have internal names like '<lambda>42'. If you get an error +for a lambda expression, you can find what it is with the following command: > + :function {'<lambda>42'} +See also: |numbered-function| + ============================================================================== 3. Internal variable *internal-variables* *E461* |