variable-assignment

c++ does implicit copy constructor copy array member variable? [duplicate]

由 别来无恙 提交于 2019-11-30 12:57:30
问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: How are C array members handled in copy control functions? I would guess implicit copy constructor (generated by compiler) would copy pointer if member variable is declared as pointer. I'm not sure what happens to array member variable. Does implicit copy constructor copy array member correctly? How about assignment operator? For instance: char mCharArray[100]; int mIntArray[100]; Would the mCharArray mIntArray

SELECT INTO with more than one attribution

由 会有一股神秘感。 提交于 2019-11-30 12:23:40
This instruction works: SELECT INTO unsolvedNodes array_agg(DISTINCT idDestination) FROM road WHERE idOrigin = ANY(solvedNodes) AND NOT (idDestination = ANY(solvedNodes)); But I would like to use something this way: SELECT INTO unsolvedNodes array_agg(DISTINCT idDestination), lengths array_agg(length) FROM road WHERE idOrigin = ANY(solvedNodes) AND NOT (idDestination = ANY(solvedNodes)); How to use only one "SELECT INTO" instruction to set multiple variables? In PL/pgSQL you can SELECT INTO as many variables at once as you like directly. You just had the syntax backwards: SELECT INTO

How to suppress “unused variable” warnings in Eclipse/PyDev

由 十年热恋 提交于 2019-11-30 11:15:45
How to suppress "unused variable" warnings in Eclipse/PyDev When I'm working with functions that return tuples, I often only need one of the values, but still want to assign to multiple variables. I would like to be able to temporarily turn this warning off so I can zero in on more serious issues. Then, I can turn it back on when doing more of a final check. If you're wondering why I would do this deliberately, it's just for readability. Say a function returns a tuple of tuples, several parts of my code might work with the third value like this: label, content = myfunc()[2] At times, I may

What does the comma in this assignment statement do?

由 筅森魡賤 提交于 2019-11-30 09:33:26
问题 I was looking through an interesting example script I found (at this site, last example line 124), and I'm struggling to understand what the comma after particles achieves in this line: particles, = ax.plot([], [], 'bo', ms=6) The script will hit an error if the comma is omitted, but the syntax (which seems to resemble an unpacking statement) does not make much sense to me, and a statement like a, = [2,3] fails, which seems like an argument against the unpacking theory. Any insight would be

Assigning an integer literal to a double variable in Java

由 倾然丶 夕夏残阳落幕 提交于 2019-11-30 09:01:10
问题 If I do the following double d = 0; since 0 is an integer literal, which uses 32 bits, and d is a double variable that uses 64 bits, will the remaining 32 bits be filled with random garbage, or does Java promote the literal correctly? 回答1: Java promotes it correctly, otherwise there'd be a rather large body of code that was problematic :-) Section 5.1.2 of the Java language spec details this: The following 19 specific conversions on primitive types are called the widening primitive

php array assign by copying value or by reference? [duplicate]

由 佐手、 提交于 2019-11-30 08:27:06
问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: are arrays in php passed by value or by reference? I heard that PHP can select how to assign arrays, depends on array size. It can assign by copying value (as any scalar type) or by reference. PHP always assign array to variables by copying a value, as it says in manual. Or it can assign by reference. ? <?php $a = array(1,2,3); ?> 回答1: Assigning arrays by reference is possible when assigning array variables to

`x = y, z` comma assignment in JavaScript [duplicate]

由 丶灬走出姿态 提交于 2019-11-30 08:21:39
Possible Duplicate: Javascript syntax: what comma means? I came across the code while reading this article (do a Ctrl + F search for Andre Breton ): //function returning array of `umbrella` fibonacci numbers function Colette(umbrella) { var staircase = 0, galleons = 0, brigantines = 1, armada = [galleons, brigantines], bassoon; Array.prototype.embrace = [].push; while(2 + staircase++ < umbrella) { bassoon = galleons + brigantines; armada.embrace(brigantines = (galleons = brigantines, bassoon)); } return armada; } What does the x = (y = x, z) construct mean? Or more specifically, what does the

Variable assignment within a for-loop [duplicate]

由 末鹿安然 提交于 2019-11-30 07:45:11
Possible Duplicate: R: How to convert string to variable name? In R, I'm writing a for-loop that will iteratively create variable names and then assign values to each variable. Here is a simplified version. The intention is to create the variable's name based on the value of iterating variable i, then fill the new variable with NA values. (I'm only iterating 1:1 below since the problem occurs isn't related to the looping itself, but rather to the way the variable is being created and assigned.) for (i in 1:1) { #name variable i "Variablei" varName = paste("Variable", as.character(i), sep="")

What does => (equals greater than) mean in Fortran?

由 ╄→尐↘猪︶ㄣ 提交于 2019-11-30 07:28:43
问题 I'm looking through some old Fortran 90 code and have come across the => symbol: var => item It looks like it's being used for some sort of assignment. Searching Google for "arrow symbol Fortran" or "equals greater than symbol Fortran" gives me no related material. 回答1: => appears in six contexts as a syntactic element in modern Fortran, many, but not all, related to pointers: pointer assignment ; pointer initialization ; procedure (pointer) declaration ; type-bound procedure declaration ;

C++ Copy constructor, temporaries and copy semantics

由 匆匆过客 提交于 2019-11-30 07:08:07
问题 For this program #include <iostream> using std::cout; struct C { C() { cout << "Default C called!\n"; } C(const C &rhs) { cout << "CC called!\n"; } }; const C f() { cout << "Entered f()!\n"; return C(); } int main() { C a = f(); C b = a; return 0; } the output I get is: Entered f()! Default C called! CC called! Since f() is returning by value, it should return a temporary. As T a = x; is T a(x); , wouldn't it call the copy constructor for the construction of a , with the temporary passed-in
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