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g++ undefined reference to typeinfo
...re missing bodies. In your class definition, something like:
virtual void foo();
Should be defined (inline or in a linked source file):
virtual void foo() {}
Or declared pure virtual:
virtual void foo() = 0;
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Compress files while reading data from STDIN
...
Yes, gzip will let you do this. If you simply run gzip > foo.gz, it will compress STDIN to the file foo.gz. You can also pipe data into it, like some_command | gzip > foo.gz.
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...
Copy folder recursively, excluding some folders
...
EXCLUDE="foo bar blah jah"
DEST=$1
for i in *
do
for x in $EXCLUDE
do
if [ $x != $i ]; then
cp -a $i $DEST
fi
do...
How do you compare structs for equality in C?
...
You may be tempted to use memcmp(&a, &b, sizeof(struct foo)), but it may not work in all situations. The compiler may add alignment buffer space to a structure, and the values found at memory locations lying in the buffer space are not guaranteed to be any particular value.
But,...
Python function attributes - uses and abuses [closed]
... that a certain method should be part of the web service interface)
class Foo(WebService):
@webmethod
def bar(self, arg1, arg2):
...
then I can define
def webmethod(func):
func.is_webmethod = True
return func
Then, when a webservice call arrives, I look up the method, ...
What is the id( ) function used for?
...ory...
This example might help you understand the concept a little more.
foo = 1
bar = foo
baz = bar
fii = 1
print id(foo)
print id(bar)
print id(baz)
print id(fii)
> 1532352
> 1532352
> 1532352
> 1532352
These all point to the same location in memory, which is why their values are...
Bash empty array expansion with `set -u`
...rsion 4.4.19(1)-release (x86_64-pc-linux-gnu)
$ set -u
$ arr=()
$ echo "foo: '${arr[@]}'"
foo: ''
There is a conditional you can use inline to achieve what you want in older versions: Use ${arr[@]+"${arr[@]}"} instead of "${arr[@]}".
$ function args { perl -E'say 0+@ARGV; say "$_: $ARGV[$_]"...
How to fallback to local stylesheet (not script) if CDN fails
...is as follows:
1) Add a special rule to the end of your CSS file, like:
#foo { display: none !important; }
2) Add the corresponding div in your HTML:
<div id="foo"></div>
3) On document ready, check whether #foo is visible or not. If the stylesheet was loaded, it will not be visib...
Is it ok to use dashes in Python files when trying to import them?
...be valid variable names ("identifiers") -- that means if you have a module foo_bar, you can use it from within Python (print foo_bar). You wouldn't be able to do so with a weird name (print foo-bar -> syntax error).
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Getting the name of a child class in the parent class (static context)
... var_dump(get_class($this));
var_dump(get_class());
}
}
class foo extends bar {
}
new foo;
?>
The above example will output:
string(3) "foo"
string(3) "bar"
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