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Why does the C preprocessor interpret the word “linux” as the constant “1”?
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In the Old Days (pre-ANSI), predefining symbols such as unix and vax was a way to allow code to detect at compile time what system it was being compiled for. There was no official language standard back then (beyond the reference material at the back of the first edition of K&R), a...
promise already under evaluation: recursive default argument reference or earlier problems?
...1, f..=f){ g.(1,T, f.=f..) }? In cases with more recursions, is it a good and safe practice adding more .? (2) if f is a non-function argument, for example g <- function(x, T, f=f){ exp(-fx/T) }* and test<- function(g.=g, T=1, f=f){ g.(1,T, f=f.) }, will using the same name for both formal a...
Is 0 a decimal literal or an octal literal?
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Yes, 0 is an Octal literal in C++.
As per the C++ Standard:
2.14.2 Integer literals [lex.icon]
integer-literal:
decimal-literal integer-suffixopt
octal-literal integer-suffixopt
hexadecimal-literal integer-suffixopt
decimal-literal:
nonzero-digit ...
How to sort an array in Bash
...set IFS
Supports whitespace in elements (as long as it's not a newline), and works in Bash 3.x.
e.g.:
$ array=("a c" b f "3 5")
$ IFS=$'\n' sorted=($(sort <<<"${array[*]}")); unset IFS
$ printf "[%s]\n" "${sorted[@]}"
[3 5]
[a c]
[b]
[f]
Note: @sorontar has pointed out that care is re...
Calling Python in Java?
... default')\nimport yourModule");
// execute a function that takes a string and returns a string
PyObject someFunc = interpreter.get("funcName");
PyObject result = someFunc.__call__(new PyString("Test!"));
String realResult = (String) result.__tojava__(String.class);
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JSON left out Infinity and NaN; JSON status in ECMAScript?
Any idea why JSON left out NaN and +/- Infinity? It puts Javascript in the strange situation where objects that would otherwise be serializable, are not, if they contain NaN or +/- infinity values.
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When to use SELECT … FOR UPDATE?
Please help me understand the use-case behind SELECT ... FOR UPDATE .
2 Answers
2
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How can I check if an argument is defined when starting/calling a batch file?
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The check for whether a commandline argument has been set can be [%1]==[], but, as Dave Costa points out, "%1"=="" will also work.
I also fixed a syntax error in the usage echo to escape the greater-than and less-than signs. In addition, the exit needs...
Django: Get an object form the DB, or 'None' if nothing matches
...orks exactly as it suppose to. It returns the first object in query result and doesn't cares if multiple results are found. If you need to check for multiple objects returned you should use .get() instead.
– Cesar Canassa
Mar 13 '14 at 15:03
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What does glLoadIdentity() do in OpenGL?
I'm new to OpenGL and I'm a little overwhelmed with all of the random functions that I have in my code. They work and I know when to use them, but I don't know why I need them or what they actually do.
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