remove-if | 易学教程

Replace/Remove characters that do not match the Regular Expression (.NET)

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问题 I have a regular expression to validate a string. But now I want to remove all the characters that do not match my regular expression. E.g. regExpression = @"^([\w\'\-\+])" text = "This is a sample text with some invalid characters -+%&()=?"; //Remove characters that do not match regExp. result = "This is a sample text with some invalid characters -+"; Any ideas of how I can use the RegExpression to determine the valid characters and remove all the other ones. Many thanks 回答1: I believe you

std::remove_if using other class method

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问题 I want to use std::remove_if with a predicate that is a member function of a differenct calss. That is class B; class A { bool invalidB( const B& b ) const; // use members of class A to verify that B is invalid void someMethod() ; }; Now, implementing A::someMethod , I have void A::someMethod() { std::vector< B > vectorB; // filling it with elements // I want to remove_if from vectorB based on predicate A::invalidB std::remove_if( vectorB.begin(), vectorB.end(), invalidB ) } Is there a way to

std::remove_if - lambda, not removing anything from the collection

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问题 Ok, I expect I've made a dumb mistake here. I have a list of DisplayDevice3d and each DisplayDevice3d contains a list of DisplayMode3d. I want to remove all items from the list of DisplayDevice3d that don't have any DisplayMode3d's. I'm trying to use a Lambda to do it, ie.: // If the device doesn't have any modes, remove it. std::remove_if(MyDisplayDevices.begin(), MyDisplayDevices.end(), [](DisplayDevice3d& device) { return device.Modes.size() == 0; } ); Even though out of 6 DisplayMode3d's

Remove object from has_many but don't delete the original record in Rails?

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I have this: Post.paragraphs << new_paragraph And I need to remove paragraph by id = 3, so the following deletes the record completely: Post.paragraphs.find(paragraph_id).destroy # or Post.paragraphs.find(paragraph_id).delete I just need to remove a paragraph from has_many association. I tried to use delete and destroy . Both methods completely delete records from the associated tables. How can I just remove them from the "container"? You should not use the delete method on the Paragraph object, but instead use the delete method of paragraphs relation, like this: post.paragraphs.delete

Removing by index from a C++ vector using remove_if

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We can use remove_if in C++ to remove elements from a vector in linear time based on a predicate that operates on the elements. bool condition(double d) {...} vector<double> data = ... std::remove_if (data.begin(), data.end(), condition); What if my condition depends not on the values, but on the indices? In other words, if I wanted to remove all the odd-indexed elements, or some arbitrary index set, etc? bool condition(int index) {//returns whether this index should be removed} vector<double> data = ... std::remove_if (data.begin(), data.end(), ???); You can use pointer arithmetic to find the

Why can't I remove a string from a std::set with std::remove_if? [duplicate]

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问题 Possible Duplicate: remove_if equivalent for std::map I have a set of strings: set <wstring> strings; // ... I wish to remove strings according to a predicate, e.g.: std::remove_if ( strings.begin(), strings.end(), []( const wstring &s ) -> bool { return s == L"matching"; }); When I attempt this, I get the following compiler error: c:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\include\algorithm(1840): error C2678: binary '=' : no operator found which takes a left-hand operand of type

std::remove_if - lambda, not removing anything from the collection

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Ok, I expect I've made a dumb mistake here. I have a list of DisplayDevice3d and each DisplayDevice3d contains a list of DisplayMode3d. I want to remove all items from the list of DisplayDevice3d that don't have any DisplayMode3d's. I'm trying to use a Lambda to do it, ie.: // If the device doesn't have any modes, remove it. std::remove_if(MyDisplayDevices.begin(), MyDisplayDevices.end(), [](DisplayDevice3d& device) { return device.Modes.size() == 0; } ); Even though out of 6 DisplayMode3d's in MyDisplayDevices, only 1 has any DisplayMode3d's in its Modes collection, nothing is being removed

Removing by index from a C++ vector using remove_if

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问题 We can use remove_if in C++ to remove elements from a vector in linear time based on a predicate that operates on the elements. bool condition(double d) {...} vector<double> data = ... std::remove_if (data.begin(), data.end(), condition); What if my condition depends not on the values, but on the indices? In other words, if I wanted to remove all the odd-indexed elements, or some arbitrary index set, etc? bool condition(int index) {//returns whether this index should be removed} vector<double

What is wrong with `std::set`?

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问题 In the other topic I was trying to solve this problem. The problem was to remove duplicate characters from a std::string . std::string s= "saaangeetha"; Since the order was not important, so I sorted s first, and then used std::unique and finally resized it to get the desired result: aeghnst That is correct! Now I want to do the same, but at the same time I want the order of characters intact. Means, I want this output: sangeth So I wrote this: template<typename T> struct is_repeated { std: