3,857 questions
0
votes
1
answer
38
views
How to model a many-to-many relationship in DynamoDB with composite keys and enforce unique (id, ruleId) pairs?
I have a DynamoDB table defined as follows:
Partition key: id (string)
Sort key: ruleId (string)
Example item:
{
"id": "123",
"ruleId": "abc"
}
What I want is ...
5
votes
0
answers
174
views
When is the ternary operator suitable for copy elision? [duplicate]
According to
this article
by Raymond Chen, ternary expression is not a copy elision candidate.
The problem with the ternary is that the ternary expression is not a copy elision candidate. The rule ...
- 1,263
14
votes
1
answer
802
views
Copy constructor is called with result of rvalue conditional operator
According to cppreference, value category of conditional operator in C++ depends on categories of the operands, namely: if both operands are lvalues, then conditional operator is also lvalue, ...
- 165
1
vote
1
answer
211
views
Why ternary operator cannot be used for this statement? [duplicate]
This code gives me compiler error: "expected an expression".
std::array< std::string, 3 > candidates = useOutname ? { "%O.log", "%O_.log", "_%O.log" } : { ...
- 2,659
0
votes
1
answer
61
views
Ternary operator initialization producing incorrect static type [duplicate]
I'm perplexed by the vscode hover hints and tsc (v5.8.3) messages I am seeing as I initialize a variable with a ternary expression that might return my trivial custom class. They seem to incorrectly ...
- 631
5
votes
2
answers
178
views
How does the `(…) and (…) or (…)` idiom mimic a ternary operator in Lua?
This statement mimics a ternary operator in the Lua programing language:
local result = condition and true_value or false_value
But how does it work? Why does it give true_value if the condition is ...
- 55
4
votes
1
answer
115
views
Error using ternary operator and method overloading of wrapper class in Java 8 only
I am using Java 8 and facing some weird error.
The compiler gives the following error:
error: reference to [method] is ambiguous
Here's my code
StringBuilder sb = new StringBuilder();
Stack<...
- 43
0
votes
1
answer
222
views
nunjucks ternary if expression
I'm using nunjucks as a templating engine in my application and can't seem to get the block to display at all when I apply more than two conditions e.g.
{{ "true" if foo else "false&...
- 111
0
votes
1
answer
91
views
pandas dataframe select rows with ternary operator
My requirement is simple, I need to select the rows from a Pandas DataFrame when one of two couple columns are populated or both. The attributes contain integer foreign keys.
This works:
...
- 141
1
vote
1
answer
80
views
How do conditional expressions group from right to left?
I checked python operator precedence (This one grammar is more detailed and more appropriate for the actual Python implementation)
Operators in the same box group left to right (except for ...
- 772
1
vote
0
answers
103
views
conditional operator with derived and base classes with conversion operator to built-in types issue, compiler bug?
This example:
struct X {};
struct Y : X {};
using CY = const Y;
true ? X() : CY(); // error
Which is explained in this answer, could be changed like this:
struct X { operator int() { return 0; } };
...
- 129
3
votes
0
answers
67
views
conditional operator: inconsistency between implicit conversion sequence used for different compilers
This is a follow-up of this question: conditional operator expression with base and const derived class doesn't compile, why?.
The core is cond ? [cv] T1() : [cv] T2() where, for instance T2 ...
- 3,479
0
votes
2
answers
738
views
What does perl substitution operator return when applied to a string?
I can't understand what does the perl substitution return after applied.
I have the following snippet
my $w = "-foo";
my $v = $w =~ s/-//?0:1;
print "---- $v\n";
If $w is -foo,...
- 311
0
votes
1
answer
83
views
Shorthand nullable variable assignment in C# [duplicate]
In my C# WPF project I am trying to assign a value to nullable short with the shorthand function:
short? var = (textbox.Text.Length > 0) ? short.Parse(textbox.Text) : null;
Visualstudio does not ...
- 3
3
votes
1
answer
117
views
Why in Java conditional expression the narrowing conversion of return type only occurs for final int and not for final short
When doing some online course, it mentioned that if we have a conditional expression in Java that returns on one side byte or short and on the other side final int, then if the int value fits into the ...
- 33