diff options
Diffstat (limited to 'doc/manual.rst')
| -rw-r--r-- | doc/manual.rst | 77 |
1 files changed, 10 insertions, 67 deletions
diff --git a/doc/manual.rst b/doc/manual.rst index de0a13143..d60d58fe7 100644 --- a/doc/manual.rst +++ b/doc/manual.rst @@ -769,8 +769,8 @@ Pre-defined floating point types The following floating point types are pre-defined: ``float`` - the generic floating point type; its size is platform dependent - (the compiler chooses the processor's fastest floating point type). + the generic floating point type; its size used to be platform dependent, + but now it is always mapped to ``float64``. This type should be used in general. floatXX @@ -1507,68 +1507,6 @@ non nilable pointers. The details of this analysis are still to be specified here. -Memory regions --------------- - -The types ``ref`` and ``ptr`` can get an optional ``region`` annotation. -A region has to be an object type. - -Regions are very useful to separate user space and kernel memory in the -development of OS kernels: - -.. code-block:: nim - type - Kernel = object - Userspace = object - - var a: Kernel ptr Stat - var b: Userspace ptr Stat - - # the following does not compile as the pointer types are incompatible: - a = b - -As the example shows ``ptr`` can also be used as a binary -operator, ``region ptr T`` is a shortcut for ``ptr[region, T]``. - -In order to make generic code easier to write ``ptr T`` is a subtype -of ``ptr[R, T]`` for any ``R``. - -Furthermore the subtype relation of the region object types is lifted to -the pointer types: If ``A <: B`` then ``ptr[A, T] <: ptr[B, T]``. This can be -used to model subregions of memory. As a special typing rule ``ptr[R, T]`` is -not compatible to ``pointer`` to prevent the following from compiling: - -.. code-block:: nim - # from system - proc dealloc(p: pointer) - - # wrap some scripting language - type - PythonsHeap = object - PyObjectHeader = object - rc: int - typ: pointer - PyObject = ptr[PythonsHeap, PyObjectHeader] - - proc createPyObject(): PyObject {.importc: "...".} - proc destroyPyObject(x: PyObject) {.importc: "...".} - - var foo = createPyObject() - # type error here, how convenient: - dealloc(foo) - - -Future directions: - -* Memory regions might become available for ``string`` and ``seq`` too. -* Builtin regions like ``private``, ``global`` and ``local`` might be - useful for an OpenCL target. -* Builtin "regions" can model ``lent`` and ``unique`` pointers. -* An assignment operator can be attached to a region so that proper write - barriers can be generated. This would imply that the GC can be implemented - completely in user-space. - - Procedural type --------------- A procedural type is internally a pointer to a procedure. ``nil`` is @@ -2337,6 +2275,8 @@ pointer type and overloading resolution is tried with ``a[]`` instead. Automatic self insertions ------------------------- +**Note**: The ``.this`` pragma is deprecated and should not be used anymore. + Starting with version 0.14 of the language, Nim supports ``field`` as a shortcut for ``self.field`` comparable to the `this`:idx: keyword in Java or C++. This feature has to be explicitly enabled via a ``{.this: self.}`` @@ -4029,9 +3969,12 @@ exception. Exception hierarchy ------------------- -The exception tree is defined in the `system <system.html>`_ module: - -.. include:: exception_hierarchy_fragment.txt +The exception tree is defined in the `system <system.html>`_ module. +Every exception inherits from ``system.Exception``. Exceptions that indicate +programming bugs inherit from ``system.Defect`` (which is a subtype of ``Exception``) +and are stricly speaking not catchable as they can also be mapped to an operation +that terminates the whole process. Exceptions that indicate any other runtime error +that can be caught inherit from ``system.Error`` (which is a subtype of ``Exception``). Imported exceptions |