大约有 48,000 项符合查询结果（耗时：0.0848秒） [XML]
What is the purpose of “&&” in a shell command?
...wo
the intent is to execute the command that follows the && only if the first command is successful. This is idiomatic of Posix shells, and not only found in Bash.
It intends to prevent the running of the second process if the first fails.
You may notice I've used the word "intent" - tha...
What is the best way to conditionally apply attributes in AngularJS?
...
Just to clarify this answer: If you prefix any attribute with ng-attr-, then the compiler will strip the prefix, and add the attribute with its value bound to the result of the angular expression from the original attribute value.
...
What’s the best way to check if a file exists in C++? (cross platform)
I have read the answers for What's the best way to check if a file exists in C? (cross platform) , but I'm wondering if there is a better way to do this using standard c++ libs? Preferably without trying to open the file at all.
...
Symfony 2: How do I check if a user is not logged in inside a template?
...
You can check if app.user is set.
{% if app.user %}
# user is logged in
{% else %}
# user is not logged in
{% endif %}
share
|
...
How to check if all elements of a list matches a condition?
...a generator expression where appropriate):
>>> [x for x in items if x[2] == 0]
[[1, 2, 0], [1, 2, 0]]
If you want to check at least one element is 0, the better option is to use any() which is more readable:
>>> any(flag == 0 for (_, _, flag) in items)
True
...
Why does string::compare return an int?
...
First, the specification is that it will return a value less
than, equal to or greater than 0, not necessarily -1 or 1.
Secondly, return values are rvalues, subject to integral
promotion, so there's no point in returning anything smaller.
...
Extract subset of key-value pairs from Python dictionary object?
... that you know the keys are going to be in the dictionary - see his answer if you aren't able to make that assumption. Alternatively, as timbo points out in the comments, if you want a key that's missing in bigdict to map to None, you can do:
{k: bigdict.get(k, None) for k in ('l', 'm', 'n')}
If...
How to limit UITableView row reordering to a section
...exPath toProposedIndexPath:(NSIndexPath *)proposedDestinationIndexPath
{
if (sourceIndexPath.section != proposedDestinationIndexPath.section) {
NSInteger row = 0;
if (sourceIndexPath.section < proposedDestinationIndexPath.section) {
row = [tableView numberOfRowsInSection:sourceInd...
Commenting multiple lines in DOS batch file
...
If you want to add REM at the beginning of each line instead of using GOTO, you can use Notepad++ to do this easily following these steps:
Select the block of lines
hit Ctrl-Q
Repeat steps to uncomment
...
Getting multiple keys of specified value of a generic Dictionary?
... IList<TFirst> firsts;
IList<TSecond> seconds;
if (!firstToSecond.TryGetValue(first, out seconds))
{
seconds = new List<TSecond>();
firstToSecond[first] = seconds;
}
if (!secondToFirst.TryGetValue(second, out firsts))
...