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Questions tagged [unary-function]

An unary function is a function that takes simply one argument. Each unary operator may also be considered an unary function.

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Why have unary_function, binary_function been removed from C++11?

I found that binary_function is removed from C++11. I am wondering why. C++98: template struct less : binary_function { bool operator() (const T& x, const T& y) const {return x struct less { …
camino
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Is There a Indirection Functor?

I'm looking for a unary functor which will dereference it's argument and return the result. Of course I can write one, it just seemed like something should already exist. So given the code: const auto vals = { 0, 1, 2, 3 }; vector…
Jonathan Mee
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boost program-options uses deprecated feature

I have boost-program-options version 1.78 installed via vcpkg. When I compile with clang++ and -std=c++20 I get the following errors. This doesn't happen when I compile with g++. According to this this std::unary_function is deprecated as of…
David Carpenter
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Passing a function object: Error

What's wrong with the following little program that passes a function object? #include #include void foo(const std::unary_function& fct) { const std::string str = "test"; fct(str); //…
Frank
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question about C pointer on boolean value,

int bar(int *arr, size_t n) { int sum = 0, i; for (i = n; i > 0; i--) { sum += !arr[i - 1]; } return ~sum + 1; } I have come across this code but don't quite understand sum += !arr[i - 1];: what is the effect of !(NOT)…
Nigel
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Is it possible to pass a literal value to a lambda unary predicate in C++?

Given the following code that does a reverse lookup on a map: map m = {{'a', 1}, {'b', 2}, {'c', 3}, {'d', 4}, {'e', 5}}; int findVal = 3; Pair v = *find_if(m.begin(), m.end(), [findVal](const Pair & p) { return…
WXB13
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Apply a unary transformer to a linkedlist

I've been working on a practice problem. The idea is that I'm supposed to take a linked list, then apply a unary transformer to the list, and return the modified list. I'm not applying a specific change, just process and return a linked list. Here's…
009
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Int++ operator isn't increasing the int the first time it's ran

Basically the goal of the program is to have the user input a number, increase is 3 times, then decrease it 3 times using unary operators. The issue is that when it's ran, the first "number is now ___" line ends up just showing the same number the…
user11287089
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What is the use of the hyphen before a function in SQL (SQLServer)

I would like to find out what the logic behind the SQL Syntax is when including a hyphen before calling a SQL function enclosed in parentheses. Here is the SQL: IF (@StartDate > @EndDate) BEGIN SET @EndDate = @StartDate SET @StartDate =…
Chanté Ana-May King
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HashMap in Unary Functional Interface with Lambda in Java 8

I'm studying for Java 8 Lambda and Unary Functional Interface. I have a practice assignment about "Function" class using HashMap, which the following steps to do: Create a variable of type Function that receives a Set and creates a…
Giacomo Brunetta
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Unary Functional Interface with Lambda in Java 8

I'm studying for Java 8 Lambda and Unary Functional Interface. I have a practice assignment about "Function" class, which the following text: 1) Create a class called "FunctionTest" with a main method 2) Create a Function variable and call it as…
Giacomo Brunetta
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Passing an iterarator to a unary predicate with std::find_if

I am trying to find the index, i, of an element of a vector, v, that satisfies: v[i] <= x < v[i + 1], where x is a given arbitrary value. I am trying to use the find_if function, but it appears that find_if passes the value from the iterator and not…
EliSquared
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Clearing std::vector of pointers with std::unary_function

In his "Effective STL" Meyers show how to clean vector of pointers correctly (std::vector::clear deletes only his pointers, and not the memory they occupy). So he advices before the call to clear use for_each with unary_function which calls object…
olha
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Problem with unary minus, in custom calculator with custom priorities

I tried making custom calculator with priorities - and / being greater then + and *. It works nearly perfectly in that manner but I come to problem with unary minus. When it removes (), rather then for example from 1 + (-3), removing + and adding…
MerHin
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How to best design function that takes an unary predicate

I'm implementing a simple timeout-class which calls a given function when time runs out. However I'm scratching my head on how to make the function constructor take an unary predicate, e.g. function pointer, std::function, functor or lambda, in the…
glades
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