Difference between revisions of "Intermediate C++ Game Programming Tutorial 16"

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(Video Timestamp Index)
(Video Timestamp Index)
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* Using the Lambda capture to bring in variables into the Lambda function [https://youtu.be/3J1Pz30IE4Q?t=13m34s 13:34]<br />- Capture syntax explained: [varl],[&var],[=],[&],[newvar=var+10],[this], capture multiple variables, mix&match capture modes <br />- Stateful Lambdas; changing captured lambda variables using the <code>mutable</code> flag [https://youtu.be/3J1Pz30IE4Q?t=15m59s 15:59]
 
* Using the Lambda capture to bring in variables into the Lambda function [https://youtu.be/3J1Pz30IE4Q?t=13m34s 13:34]<br />- Capture syntax explained: [varl],[&var],[=],[&],[newvar=var+10],[this], capture multiple variables, mix&match capture modes <br />- Stateful Lambdas; changing captured lambda variables using the <code>mutable</code> flag [https://youtu.be/3J1Pz30IE4Q?t=15m59s 15:59]
 
* Some anxiety-reducing consolation by Chili [https://youtu.be/3J1Pz30IE4Q?t=16m40s 16:40]
 
* Some anxiety-reducing consolation by Chili [https://youtu.be/3J1Pz30IE4Q?t=16m40s 16:40]
* Syntax for a callable Lambda function [https://youtu.be/3J1Pz30IE4Q?t=17m03s 17:03] <br />- Make it callable once: <code>[...](...){...}(vec.front());</code>, functor is destroyed immediately<br />- Keep the functor using <code>auto mylamb = [...](...){...};</code>, which can be called by <code>bool result = mylamb(vec.front())</code>, or <code>std::remove_if(...,...,mylamb);</code>
+
* Syntax for a callable Lambda function [https://youtu.be/3J1Pz30IE4Q?t=17m03s 17:03] <br />- Make it callable once: <code>[...](...){...}(vec.front());</code>, functor is destroyed immediately<br />- Keep the functor using <code>auto mylamb = [...](...){...};</code>, which can be called by <code>bool result = mylamb(vec.front());</code>, or <code>std::remove_if(...,...,mylamb);</code>
 
* The power of C++ is in its flexibility. Example code for converting a string to lowercase:<br /><code>std::transform(str.begin(),str.end(),str.begin(),::tolower);</code>[https://youtu.be/3J1Pz30IE4Q?t=17m49s 17:49]
 
* The power of C++ is in its flexibility. Example code for converting a string to lowercase:<br /><code>std::transform(str.begin(),str.end(),str.begin(),::tolower);</code>[https://youtu.be/3J1Pz30IE4Q?t=17m49s 17:49]
 
* Homework assignment [https://youtu.be/3J1Pz30IE4Q?t=18m39s 18:39]
 
* Homework assignment [https://youtu.be/3J1Pz30IE4Q?t=18m39s 18:39]

Revision as of 05:25, 29 September 2019

In the video we take a look at a couple of bangers from <algorithm>, and we learn what lambda functions are and how to use them.

Topics Covered

  • Algorithms std::sort and std::remove_if
  • Concepts (as in, type concepts like Comparable)
  • <functional> functors as predicates
  • Lambda functions

Errata

In the video Chili states that std::remove does not preserve the relative order of elements in the container, but this is fake news! Relative order is preserved: [1]

Video Timestamp Index

Tutorial 16

  • Generic Algorithms: how Templates and Iterators make Algorithms independent of Data Types and Containers 0:17
  • The std::sort algorithm and its requirements 0:43
  • Sorting a (forward) list std::list, using its member function std::list::sort() 2:16
  • Introducing Concepts / named requirements of types (e.g., the Compare requirement of std::sort) 2:54
  • Modyfing sorting order by passing a comparison function object (functor) as a predicate, like so:
    std::sort(vec.begin(),vec.end(),std::greater<int>{}); 3:17
    Note: vec is a std::vector of integers
  • Sort custom types, example code for sorting a custom class object by creating a functor, called like so:
    std::sort(vecObj.begin(),vecObj.end(),Obj::YLess{}); 4:07
  • Removing items from a container, std::remove and std::remove_if 6:11
    - Create a functor as a unary predicate for the std::remove function to remove elements using a threshold variable 8:28
    - Use container member function erase() to correct the endpoint of the container after the remove operation 9:51
  • Introducing Lambda functions to replace custom functors 11:51
  • Using the Lambda capture to bring in variables into the Lambda function 13:34
    - Capture syntax explained: [varl],[&var],[=],[&],[newvar=var+10],[this], capture multiple variables, mix&match capture modes
    - Stateful Lambdas; changing captured lambda variables using the mutable flag 15:59
  • Some anxiety-reducing consolation by Chili 16:40
  • Syntax for a callable Lambda function 17:03
    - Make it callable once: [...](...){...}(vec.front());, functor is destroyed immediately
    - Keep the functor using auto mylamb = [...](...){...};, which can be called by bool result = mylamb(vec.front());, or std::remove_if(...,...,mylamb);
  • The power of C++ is in its flexibility. Example code for converting a string to lowercase:
    std::transform(str.begin(),str.end(),str.begin(),::tolower);17:49
  • Homework assignment 18:39
  • Introducing the Algorithm STD Gems series that takes a deep dive into its functionality 19:20

Homework

Solve the problems in Source.cpp attached below using the <algorithm> library and other parts of the standard library as extensively as possible. As a bonus problem, implement the sprite drawing effect shown at the end of the video using a lambda function.

Related Series

For an in-depth look into the <algorithm> library and beyond, check out STD Gems.

Links

Algorithms Library

See also