大约有 40,000 项符合查询结果（耗时：0.0350秒） [XML]
Why check both isset() and !empty()
...
This is completely redundant. empty is more or less shorthand for !isset($foo) || !$foo, and !empty is analogous to isset($foo) && $foo. I.e. empty does the reverse thing of isset plus an additional check for the truthiness of a value.
Or in other words, empty is the same as !$foo, but d...
How to write a switch statement in Ruby
...sing the === operator. For example, 1..5 === x, and not x === 1..5.
This allows for sophisticated when clauses as seen above. Ranges, classes and all sorts of things can be tested for rather than just equality.
Unlike switch statements in many other languages, Ruby’s case does not have fall-thr...
Is SQL syntax case sensitive?
... are case-insensitive (SELECT, FROM, WHERE, etc), but are often written in all caps. However in some setups table and column names are case-sensitive. MySQL has a configuration option to enable/disable it. Usually case-sensitive table and column names are the default on Linux MySQL and case-insensit...
How to use XPath in Python?
... node set size"
sys.exit(1)
if res[0].name != "doc" or res[1].name != "foo":
print "xpath query: wrong node set value"
sys.exit(1)
doc.freeDoc()
ctxt.xpathFreeContext()
Sample of ElementTree XPath Use
from elementtree.ElementTree import ElementTree
mydoc = ElementTree(file='tst.xml'...
Why is there no logical xor in JavaScript?
...r. Mainly because it's not useful. Bitwise XOR is extremely useful, but in all my years of programming I have never needed a logical XOR.
If you have two boolean variables you can mimic XOR with:
if (a != b)
With two arbitrary variables you could use ! to coerce them to boolean values and then u...
Why can't C# interfaces contain fields?
For example, suppose I want an ICar interface and that all implementations will contain the field Year . Does this mean that every implementation has to separately declare Year ? Wouldn't it be nicer to simply define this in the interface?
...
Is #pragma once a safe include guard?
...
It shouldn't be any slower at all (with GCC anyway).
– Jason Coco
Apr 24 '09 at 21:07
54
...
C++, copy set to vector
...hold the input range.
std::back_inserter creates an output iterator that calls push_back on a container for each element, so each element is inserted into the container. Alternatively, you could have created a sufficient number of elements in the std::vector to hold the range being copied:
std::v...
Meaning of “[: too many arguments” error from if [] (square brackets)
...
# if [ hello world == 0 ]
fi
The same will be true for any function call that puts down a string containing spaces or other special characters.
Easy fix
Wrap the variable output in double quotes, forcing it to stay as one string (therefore one argument). For example,
VARIABLE=$(/some/comm...
How to get the current working directory in Java?
...
@ubuntudroid: that's why i mentioned specifically that it will print the path from where the application had initialized. My guess the thread starter directly run the jar/program after starting commnad prompt (which is basically at C:\WINDOWS\system32). I hope you under...