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Merge pull request #315 from gradha/pr_adds_example_of_addr_cast_usage

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Adds example of addr/cast usage and indexes addr.
This commit is contained in:
Araq 2013-01-23 13:22:06 -08:00
commit 3462040d39
3 changed files with 29 additions and 17 deletions
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27
doc/manual.txt
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@ -2232,7 +2232,6 @@ Type casts
----------
Example:
.. code-block:: nimrod
cast[int](x)
@ -2243,11 +2242,27 @@ only needed for low-level programming and are inherently unsafe.
The addr operator
-----------------
The `addr` operator returns the address of an l-value. If the
type of the location is ``T``, the `addr` operator result is
of the type ``ptr T``. Taking the address of an object that resides
on the stack is **unsafe**, as the pointer may live longer than the
object on the stack and can thus reference a non-existing object.
The `addr`:idx: operator returns the address of an l-value. If the type of the
location is ``T``, the `addr` operator result is of the type ``ptr T``. An
address is always an untraced reference. Taking the address of an object that
resides on the stack is **unsafe**, as the pointer may live longer than the
object on the stack and can thus reference a non-existing object. You can get
the address of variables, but you can't use it on variables declared through
``let`` statements:
.. code-block:: nimrod
let t1 = "Hello"
var
t2 = t1
t3 : pointer = addr(t2)
echo repr(addr(t2))
# --> ref 0x7fff6b71b670 --> 0x10bb81050"Hello"
echo cast[ptr string](t3)[]
# --> Hello
# The following line doesn't compile:
echo repr(addr(t1))
# Error: expression has no address
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