changed to {.experimental: codeReordering.}, postpoing declared() stuff
This commit is contained in:
parent
47726ecb9e
commit
32deb70bae
1 changed files with 105 additions and 97 deletions
202
doc/manual.rst
202
doc/manual.rst
|
|
@ -6418,6 +6418,111 @@ iterator in which case the overloading resolution takes place:
|
||||||
var x = 4
|
var x = 4
|
||||||
write(stdout, x) # not ambiguous: uses the module C's x
|
write(stdout, x) # not ambiguous: uses the module C's x
|
||||||
|
|
||||||
|
Code reordering
|
||||||
|
~~~~~~~~~~~~~~~
|
||||||
|
|
||||||
|
**Note**: Code reordering is experimental and must be enabled via the
|
||||||
|
``{.experimental.}`` pragma.
|
||||||
|
|
||||||
|
The code reordering feature can implicitly rearrange procedure, template, and
|
||||||
|
macro definitions along with variable declarations and initializations at the top
|
||||||
|
level scope so that, to a large extent, a programmer should not have to worry
|
||||||
|
about ordering definitions correctly or be forced to use forward declarations to
|
||||||
|
preface definitions inside a module.
|
||||||
|
|
||||||
|
..
|
||||||
|
NOTE: The following was documentation for the code reordering precursor,
|
||||||
|
which was {.noForward.}.
|
||||||
|
|
||||||
|
In this mode, procedure definitions may appear out of order and the compiler
|
||||||
|
will postpone their semantic analysis and compilation until it actually needs
|
||||||
|
to generate code using the definitions. In this regard, this mode is similar
|
||||||
|
to the modus operandi of dynamic scripting languages, where the function
|
||||||
|
calls are not resolved until the code is executed. Here is the detailed
|
||||||
|
algorithm taken by the compiler:
|
||||||
|
|
||||||
|
1. When a callable symbol is first encountered, the compiler will only note
|
||||||
|
the symbol callable name and it will add it to the appropriate overload set
|
||||||
|
in the current scope. At this step, it won't try to resolve any of the type
|
||||||
|
expressions used in the signature of the symbol (so they can refer to other
|
||||||
|
not yet defined symbols).
|
||||||
|
|
||||||
|
2. When a top level call is encountered (usually at the very end of the
|
||||||
|
module), the compiler will try to determine the actual types of all of the
|
||||||
|
symbols in the matching overload set. This is a potentially recursive process
|
||||||
|
as the signatures of the symbols may include other call expressions, whose
|
||||||
|
types will be resolved at this point too.
|
||||||
|
|
||||||
|
3. Finally, after the best overload is picked, the compiler will start
|
||||||
|
compiling the body of the respective symbol. This in turn will lead the
|
||||||
|
compiler to discover more call expressions that need to be resolved and steps
|
||||||
|
2 and 3 will be repeated as necessary.
|
||||||
|
|
||||||
|
Please note that if a callable symbol is never used in this scenario, its
|
||||||
|
body will never be compiled. This is the default behavior leading to best
|
||||||
|
compilation times, but if exhaustive compilation of all definitions is
|
||||||
|
required, using ``nim check`` provides this option as well.
|
||||||
|
|
||||||
|
Example:
|
||||||
|
|
||||||
|
.. code-block:: nim
|
||||||
|
|
||||||
|
{.experimental: "codeReordering".}
|
||||||
|
|
||||||
|
proc foo(x: int) =
|
||||||
|
bar(x)
|
||||||
|
|
||||||
|
proc bar(x: int) =
|
||||||
|
echo(x)
|
||||||
|
|
||||||
|
foo(10)
|
||||||
|
|
||||||
|
Variables can also be reordered as well. Keep in mind, when we initialize (i.e.
|
||||||
|
combined declaration and assignment in one statement) variables, that entire
|
||||||
|
statement itself may be reordered. Be wary of what code you execute at the top
|
||||||
|
level:
|
||||||
|
|
||||||
|
.. code-block:: nim
|
||||||
|
{.experimental: "codeReordering".}
|
||||||
|
|
||||||
|
proc a() =
|
||||||
|
echo(foo)
|
||||||
|
|
||||||
|
var foo = 5
|
||||||
|
|
||||||
|
a() # outputs: "5"
|
||||||
|
|
||||||
|
..
|
||||||
|
TODO: Let's table this for now. This is an *experimental feature* and so the
|
||||||
|
specific manner in which ``declared`` operates with it can be decided in
|
||||||
|
eventuality.
|
||||||
|
|
||||||
|
The values of expressions involving ``declared`` are decided *before* the
|
||||||
|
code reordering process, and not after. As an example, the output of this
|
||||||
|
code is the same as it would be with code reordering disabled.
|
||||||
|
|
||||||
|
.. code-block:: nim
|
||||||
|
{.experimental: "codeReordering".}
|
||||||
|
|
||||||
|
proc x() =
|
||||||
|
echo(declared(foo))
|
||||||
|
|
||||||
|
var foo = 4
|
||||||
|
|
||||||
|
x() # "false"
|
||||||
|
|
||||||
|
It is important to note that reordering *only* works for symbols at top level
|
||||||
|
scope. Therefore, the following will *fail to compile:*
|
||||||
|
|
||||||
|
.. code-block:: nim
|
||||||
|
{.experimental: "codeReordering".}
|
||||||
|
|
||||||
|
proc a() =
|
||||||
|
b()
|
||||||
|
proc b() =
|
||||||
|
echo("Hello!")
|
||||||
|
|
||||||
|
a()
|
||||||
|
|
||||||
Compiler Messages
|
Compiler Messages
|
||||||
=================
|
=================
|
||||||
|
|
@ -6825,103 +6930,6 @@ and before any variable in a module that imports it.
|
||||||
|
|
||||||
reorder pragma
|
reorder pragma
|
||||||
--------------
|
--------------
|
||||||
**Note**: Code reordering is experimental. By default it is turned off.
|
|
||||||
|
|
||||||
The ``reorder`` pragma can be used to turn on and off a special compilation mode
|
|
||||||
that aims to be able to implicitly rearrange procedure, template, and macro
|
|
||||||
definitions along with variable declarations and initializations at the top
|
|
||||||
level scope so that, to a large extent, a programmer should not have to worry
|
|
||||||
about ordering definitions correctly or be forced to use forward declarations to
|
|
||||||
preface definitions inside a module.
|
|
||||||
|
|
||||||
..
|
|
||||||
NOTE: The following was documentation for the precursor to {.reorder.},
|
|
||||||
which was {.noForward.}.
|
|
||||||
|
|
||||||
In this mode, procedure definitions may appear out of order and the compiler
|
|
||||||
will postpone their semantic analysis and compilation until it actually needs
|
|
||||||
to generate code using the definitions. In this regard, this mode is similar
|
|
||||||
to the modus operandi of dynamic scripting languages, where the function
|
|
||||||
calls are not resolved until the code is executed. Here is the detailed
|
|
||||||
algorithm taken by the compiler:
|
|
||||||
|
|
||||||
1. When a callable symbol is first encountered, the compiler will only note
|
|
||||||
the symbol callable name and it will add it to the appropriate overload set
|
|
||||||
in the current scope. At this step, it won't try to resolve any of the type
|
|
||||||
expressions used in the signature of the symbol (so they can refer to other
|
|
||||||
not yet defined symbols).
|
|
||||||
|
|
||||||
2. When a top level call is encountered (usually at the very end of the
|
|
||||||
module), the compiler will try to determine the actual types of all of the
|
|
||||||
symbols in the matching overload set. This is a potentially recursive process
|
|
||||||
as the signatures of the symbols may include other call expressions, whose
|
|
||||||
types will be resolved at this point too.
|
|
||||||
|
|
||||||
3. Finally, after the best overload is picked, the compiler will start
|
|
||||||
compiling the body of the respective symbol. This in turn will lead the
|
|
||||||
compiler to discover more call expressions that need to be resolved and steps
|
|
||||||
2 and 3 will be repeated as necessary.
|
|
||||||
|
|
||||||
Please note that if a callable symbol is never used in this scenario, its
|
|
||||||
body will never be compiled. This is the default behavior leading to best
|
|
||||||
compilation times, but if exhaustive compilation of all definitions is
|
|
||||||
required, using ``nim check`` provides this option as well.
|
|
||||||
|
|
||||||
Example:
|
|
||||||
|
|
||||||
.. code-block:: nim
|
|
||||||
|
|
||||||
{.reorder: on.}
|
|
||||||
|
|
||||||
proc foo(x: int) =
|
|
||||||
bar(x)
|
|
||||||
|
|
||||||
proc bar(x: int) =
|
|
||||||
echo(x)
|
|
||||||
|
|
||||||
foo(10)
|
|
||||||
|
|
||||||
Variables can also be reordered as well. Keep in mind, when we initialize (i.e.
|
|
||||||
combined declaration and assignment in one statement) variables, that entire
|
|
||||||
statement itself may be reordered. Be wary of what code you execute at the top
|
|
||||||
level:
|
|
||||||
|
|
||||||
.. code-block:: nim
|
|
||||||
{.reorder: on.}
|
|
||||||
|
|
||||||
proc a() =
|
|
||||||
echo(foo)
|
|
||||||
|
|
||||||
var foo = 5
|
|
||||||
|
|
||||||
a() # outputs: "5"
|
|
||||||
|
|
||||||
The values of expressions involving `declared` are decided *before* the code
|
|
||||||
reordering process, and not after. As an example, the output of this code is
|
|
||||||
the same as it would be with code reordering disabled.
|
|
||||||
|
|
||||||
.. code-block:: nim
|
|
||||||
{.reorder: on.}
|
|
||||||
|
|
||||||
proc x() =
|
|
||||||
echo(declared(foo))
|
|
||||||
|
|
||||||
var foo = 4
|
|
||||||
|
|
||||||
x() # "false"
|
|
||||||
|
|
||||||
It is important to note that reordering *only* works for symbols at top level
|
|
||||||
scope. Therefore, the following will *fail to compile:*
|
|
||||||
|
|
||||||
.. code-block:: nim
|
|
||||||
{.reorder: on.}
|
|
||||||
|
|
||||||
proc a() =
|
|
||||||
b()
|
|
||||||
proc b() =
|
|
||||||
echo("Hello!")
|
|
||||||
|
|
||||||
a()
|
|
||||||
|
|
||||||
pragma pragma
|
pragma pragma
|
||||||
-------------
|
-------------
|
||||||
|
|
|
||||||
Loading…
Add table
Add a link
Reference in a new issue