Questions tagged [lambda]
DO NOT USE FOR THE AWS SERVICE (use [aws-lambda] for those questions!) Lambdas are anonymous functions or closures in programming languages such as Lisp, C#, C++, Lua, Python, Ruby, JavaScript, Java, Excel or Google sheets. (Also, lambda expression.)
lambda
30,121
questions
-3
votes
1
answer
52
views
Does filter have a way to export the "list" one element at a time?
On a practice exercise about prime numbers I found out that filter does not return a list itself and I need to do:
list(filter())
to obtain that list.
I do the exercise twice, once with a for loop:
...
-1
votes
0
answers
28
views
GoogleSheets ordering matrix columns of 3
I have a dataset organized into 3 columns, being the first row the title.
Data is organized by category DC,PH,DA,PF and date. But imputed in a randomly order
Notice there are 147 columns and 127 rows, ...
- 9
0
votes
2
answers
45
views
Transformations on Multiple Columns in Pandas Dataframe
Using the pandas framework in Python, I need to apply a transformation on 4 columns (Col1, Col2, Col3, Col4 in example Code) in a table.
The Transformation is quite simple:
Extract a Unix Timestamp
...
- 153
0
votes
2
answers
42
views
Building a C# equivalent of the SQL Server construct IN?
Often in SQL Server, I use IN to check if a value is in a list of items, for example:
WHERE @x IN (1, 2, 3, 5, 8, 13)
I've got as close as I can by defining the following in a library function, thus:
...
- 525
0
votes
1
answer
36
views
Building a generic search for RavenDb - failing to create Expression<Func<T,object>>
The standard search method on IRavenQueryable looks like this:
public static IRavenQueryable<T> Search<T>(this IQueryable<T> self, Expression<Func<T, object>> ...
- 1,221
2
votes
1
answer
112
views
In GCC, inside a lambda, I can get constexpr variable from a non-constexpr template lambda, but not in Visual C++
This code compiles fine in gcc, but fail in Visual C++.
MCVE = https://godbolt.org/z/K7d5PEs65
int main(){
int localVariable=0; //some local variable
auto lamb=[&]<int s>() {
...
- 1,114
1
vote
2
answers
60
views
get constexpr variable from a lambda function is fine , but compile fail (Visual C++) and fine (gcc) when such statement is in a new lambda
This code compiles fine in gcc, but fail in Visual C++.
MCVE = https://wandbox.org/permlink/SqNI85EospSrwm5T
int main() {
auto func_do1Pass2=[&]() {
return 8;
};
constexpr int ...
- 1,114
0
votes
1
answer
115
views
What is the type of a templated lambda?
The following code tries to create a templated lambda and pass it to a function that calls it. However compilation fails because the type of lambda argument is wrong.
#include <functional>
void ...
- 534
1
vote
1
answer
56
views
Ternary operator not working inside Lambda function Ruby
I am trying to write a Lambda function in Ruby, to calculate the nth Fibonacci number.
fib = -> (n) { n in [1, 2] ? 1 : fib.[n - 1] + fib.[n - 2] }
This gives me the error,
./fib.rb:3: warning: ...
- 57
0
votes
1
answer
102
views
building generic property selector / setter in C# if you only know the type at runtime [duplicate]
I'm working with API that want expressions as parameters to identitfy/modify properties on an object. This works fine if I know the type at compile Time. E.g. the APi requires an Expression<Func<...
- 1,221
0
votes
2
answers
75
views
What does "lambda x: x-0 and x-1" mean? [duplicate]
What does the expression do?
my_tuple = (0, 1, 2, 3, 4, 5)
foo = list(filter(lambda x: x-0 and x-1, my_tuple))
print(foo)
What output is to be expected from above equation?
- 11
-1
votes
1
answer
60
views
LINQ query where clause in list
I am trying to limit the data returned via a repository using the where clause based on a list of values.
I have a PurchaseOrders entity where I want to return all purchase orders that have an ...
- 35
1
vote
1
answer
91
views
how to convert lambda function to another one taking tuple of parameters
I need to create a wrapper for lambda function that would take a tuple of parameters of the original lambda function and use its implementation. I'm using C++23 compiler. This is the function I came ...
- 397
2
votes
0
answers
43
views
"Leaked in-place lambda" warning after an upgrade to Kotlin 2.0
Consider the following Kotlin code which overloads Reader.useLines(). The 1st extension merely invokes Reader.useLines() and has an exactly the same contract, the 2nd one filters the line sequence ...
- 5,222
3
votes
0
answers
63
views
For function definition, what is the difference between using partial application, a lamba expression or put the arguments next to the name? [duplicate]
What are the differences between the three syntaxes
funName l = map fun l
funName = \ l -> map fun l
funName = map fun
In general it does the same thing however in some cases it differs.
The ...
