variable-assignment | 易学教程

GO explicit array initialization

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问题 Is there explicit array initialization (declaration and assignment) in GO or the only way is using the shorthand operator? Here is a practical example - is this two equal: a := [3]int{1, 0, 1} var a [3]int = [3]int{1, 0, 1} 回答1: They are equivalent. In general: Spec: Short variable declaration: A short variable declaration uses the syntax: ShortVarDecl = IdentifierList ":=" ExpressionList . It is shorthand for a regular variable declaration with initializer expressions but no types: "var"

Julia: Assignment in Arrays

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问题 When indexing more than one level for an array, it works fine. But when I used it to assign values, it did not. Does anyone know why A does not change below? In [4]: A = rand(6) Out [4]: 6-element Array{Float64,1}: 0.111552 0.155126 0.78485 0.147477 0.362078 0.959022 In [5]: A[3:5][[true,false,true]] Out [5]: 2-element Array{Float64,1}: 0.78485 0.362078 In [6]: A[3:5][[true,false,true]] = [99, 999] Out [6]: 2-element Array{Int64,1}: 99 999 In [7]: A Out [7]: 6-element Array{Float64,1}: 0

Cell assignment of a 2-dimensional Matrix in Python, without numpy

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问题 Below is my script, which basically creates a zero matrix of 12x8 filled with 0. Then I want to fill it in, one by one. So lets say column 2 row 0 needs to be 5. How do I do that? The example below shows how I did it and the wrong (for my needs) output: list_MatrixRow = [] list_Matrix = [] #Not to be confused by what the book calls, optimal alignment score matrix int_NumbOfColumns = 12 int_NumbOfRows = 8 for i in range (0, int_NumbOfColumns): # Puts Zeros across the first Row list

<?= operator C++ greater less question mark equals sign

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问题 I saw <?= and >?= used in a code: http://community.topcoder.com/stat?c=problem_solution&rm=151152&rd=5854&pm=2923&cr=310333 I tried to compile without the includes to test if it's standard, but it didn't work. I then added the includes, but it still gives the same error: question-mark.cpp:15:5: error: expected primary-expression before ‘?’ token question-mark.cpp:15:6: error: expected primary-expression before ‘=’ token question-mark.cpp:15:9: error: expected ‘:’ before ‘;’ token question

Python: Assigning “through” an iterator

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问题 I have an iterator over a mutable sequence, e.g. foo = [1,2,3,4,5] for bar in foo: Is there a way to write to the elements in foo by using the reference which is contained in the iterator? The naive assignment: bar = 42 does not work of course. Is it possible to use the "behind the curtain" reference to the sequence element which is in the iterator ? PS: The simple solution with using an index for i in range(len(a)): a[i] = 42 will not work for my case, as I can't expose the container name.

Multiassignment in VB like in C-Style languages

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问题 Is there a way to perform this in VB.NET like in the C-Style languages: struct Thickness { double _Left; double _Right; double _Top; double _Bottom; public Thickness(double uniformLength) { this._Left = this._Right = this._Top = this._Bottom = uniformLength; } } 回答1: Expanding on Mark's correct answer This type of assignment style is not possible in VB.Net. The C# version of the code works because in C# assignment is an expression which produces a value. This is why it can be chained in this

List Assignment in Scalar Context

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问题 A list assignment in scalar context returns the number of elements on the right hand side: scalar(my ($hello, $there, $world) = (7,8)); #evaluates to 2 Why does it evaluate the right hand side and produce 2, instead of the newly defined list being evaluated and returning 3? To me, it seems like $hello gets 7, $there gets 8, and $world gets undef , then that list is evaluated in scalar context, which would result in 3, as that is the number of elements in the list ( $hello $there $world ). It

Assignment statement value

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问题 Everybody knows that in Python assignments do not return a value, presumably to avoid assignments on if statements when usually just a comparison is intended: >>> if a = b: File "<stdin>", line 1 if a = b: ^ SyntaxError: invalid syntax >>> if a == b: ... pass ... For the same reason, one could suspect that multiple assignments on the same statement were also syntax errors. In fact, a = (b = 2) is not a valid expression: >>> a = (b = 2) File "<stdin>", line 1 a = (b = 2) ^ SyntaxError: invalid

Partially initializing a C struct

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问题 This link states that "When an automatic array or structure has a partial initializer, the remainder is initialized to 0". I decided to try out what I read and wrote the following piece of code: #include <stdio.h> #include <string.h> #include <stdlib.h> int main(void) { //int arr[3] = {2}; // line no. 7 struct s { int si; int sj; }; struct s myStruct; myStruct.si = 9; printf("%d\n", myStruct.sj); } I don't understand why 4096 (which I believe is some "garbage" value) is printed when I comment

Why do class variables in Javascript disappear when trying to call them multiple times or assigning them to local variables?

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var width = 10; var data = image.data; var height = 10; for ( var x = 0; x < width; x++ ) { for ( var y = 0; y < height; y++ ) var index = 4 * (y * height + x); // 0 var local_variable = ArbitraryClassInstance.getBrightness(x, y); // 0 data[ index ] = ArbitraryClassInstance.getBrightness(x, y); // 0 for both index/call data[ index + 1 ] = ArbitraryClassInstance.getBrightness(x, y); // 0 for both index/call } } context.putImageData(image, 0, 0); Both index and local_variable are equalled to zero when I execute the code. Image is a javascript image object, data is the image data, and width and