diff options
Diffstat (limited to 'doc/manual.rst')
| -rw-r--r-- | doc/manual.rst | 32 |
1 files changed, 21 insertions, 11 deletions
diff --git a/doc/manual.rst b/doc/manual.rst index a7bca7616..da50e2c56 100644 --- a/doc/manual.rst +++ b/doc/manual.rst @@ -2458,12 +2458,13 @@ matches) is preferred: gen(ri) # "ref T" -Overloading based on 'var T' ----------------------------- +Overloading based on 'var T' / 'out T' +-------------------------------------- -If the formal parameter ``f`` is of type ``var T`` in addition to the ordinary -type checking, the argument is checked to be an `l-value`:idx:. ``var T`` -matches better than just ``T`` then. +If the formal parameter ``f`` is of type ``var T`` (or ``out T``) +in addition to the ordinary +type checking, the argument is checked to be an `l-value`:idx:. +``var T`` (or ``out T``) matches better than just ``T`` then. .. code-block:: nim proc sayHi(x: int): string = @@ -2482,6 +2483,17 @@ matches better than just ``T`` then. # 13 +An l-value matches ``var T`` and ``out T`` equally well, hence +the following is ambiguous: + +.. code-block:: nim + + proc p(x: out string) = x = "" + proc p(x: var string) = x = "" + var v: string + p(v) # ambiguous + + Lazy type resolution for untyped -------------------------------- @@ -4230,9 +4242,7 @@ error message from ``e``, and for such situations it is enough to use Custom exceptions ----------------- -Is it possible to create custom exceptions. These make it easy to distinguish between exceptions raised by nim and those from your own code. - -A custom exception is a custom type: +Is it possible to create custom exceptions. A custom exception is a custom type: .. code-block:: nim type @@ -4782,7 +4792,7 @@ of "typedesc"-ness is stripped off: Generic inference restrictions ------------------------------ -The types ``var T`` and ``typedesc[T]`` cannot be inferred in a generic +The types ``var T``, ``out T`` and ``typedesc[T]`` cannot be inferred in a generic instantiation. The following is not allowed: .. code-block:: nim @@ -5930,7 +5940,7 @@ noSideEffect pragma The ``noSideEffect`` pragma is used to mark a proc/iterator to have no side effects. This means that the proc/iterator only changes locations that are reachable from its parameters and the return value only depends on the -arguments. If none of its parameters have the type ``var T`` +arguments. If none of its parameters have the type ``var T`` or ``out T`` or ``ref T`` or ``ptr T`` this means no locations are modified. It is a static error to mark a proc/iterator to have no side effect if the compiler cannot verify this. @@ -6593,7 +6603,7 @@ during semantic analysis: Emit pragma ----------- The ``emit`` pragma can be used to directly affect the output of the -compiler's code generator. So it makes your code unportable to other code +compiler's code generator. The code is then unportable to other code generators/backends. Its usage is highly discouraged! However, it can be extremely useful for interfacing with `C++`:idx: or `Objective C`:idx: code. |