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

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== <span style="color:red">Errata</span> ==
 
== <span style="color:red">Errata</span> ==
 
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: [https://en.cppreference.com/w/cpp/algorithm/remove]
 
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: [https://en.cppreference.com/w/cpp/algorithm/remove]
 +
 +
In the homework solution there is a part where Chili uses an iterator into a <code>stringstream</code> [https://youtu.be/_1-iES-Eytc?t=626]. This code no longer works due to changes (improvements) to the Visual Studio compiler. Basically, you cannot pass a temporary stream into the iterator constructor. See this: [https://stackoverflow.com/questions/23714445/passing-temporary-istringstream-object-to-istream-iteratorstring]
  
 
== Video Timestamp Index ==
 
== Video Timestamp Index ==
 
[https://youtu.be/3J1Pz30IE4Q Tutorial 16]
 
[https://youtu.be/3J1Pz30IE4Q Tutorial 16]
 +
<div class="mw-collapsible mw-collapsed"><br />
 
* Generic Algorithms: how Templates and Iterators make Algorithms independent of Data Types and Containers [https://youtu.be/3J1Pz30IE4Q?t=17s 0:17]
 
* Generic Algorithms: how Templates and Iterators make Algorithms independent of Data Types and Containers [https://youtu.be/3J1Pz30IE4Q?t=17s 0:17]
 
* The <code>std::sort</code> algorithm and its requirements [https://youtu.be/3J1Pz30IE4Q?t=43s 0:43]
 
* The <code>std::sort</code> algorithm and its requirements [https://youtu.be/3J1Pz30IE4Q?t=43s 0:43]
 
* Sorting a (forward) list <code>std::list</code>, using its member function <code>std::list::sort()</code> [https://youtu.be/3J1Pz30IE4Q?t=2m16s 2:16]
 
* Sorting a (forward) list <code>std::list</code>, using its member function <code>std::list::sort()</code> [https://youtu.be/3J1Pz30IE4Q?t=2m16s 2:16]
* Introducing Concepts / named requirements of types (e.g., the <code>Compare</code> requirement of <code>std::sort</code> [https://youtu.be/3J1Pz30IE4Q?t=2m54s 2:54]
+
* Introducing Concepts / named requirements of types (e.g., the <code>Compare</code> requirement of <code>std::sort</code>) [https://youtu.be/3J1Pz30IE4Q?t=2m54s 2:54]
 
* Modyfing sorting order by passing a comparison function object (functor) as a predicate, like so:<br /><code>std::sort(vec.begin(),vec.end(),std::greater<int>{});</code> [https://youtu.be/3J1Pz30IE4Q?t=3m17s 3:17]<br />Note: vec is a std::vector of integers
 
* Modyfing sorting order by passing a comparison function object (functor) as a predicate, like so:<br /><code>std::sort(vec.begin(),vec.end(),std::greater<int>{});</code> [https://youtu.be/3J1Pz30IE4Q?t=3m17s 3:17]<br />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: <br /><code>std::sort(vecObj.begin(),vecObj.end(),Obj::YLess{});</code> [https://youtu.be/3J1Pz30IE4Q?t=4m07s 4:07]
 
* Sort custom types, example code for sorting a custom class object by creating a functor, called like so: <br /><code>std::sort(vecObj.begin(),vecObj.end(),Obj::YLess{});</code> [https://youtu.be/3J1Pz30IE4Q?t=4m07s 4:07]
* Removing items from a container, <code>std::remove</code> and <code>std::remove_if</code> [https://youtu.be/3J1Pz30IE4Q?t=6m11s 6:11] <br />- Create a functor as a unary predicate for the <code>std::remove</code> function to remove elements using a threshold variable [https://youtu.be/3J1Pz30IE4Q?t=8m28s 8:28] <br />- Use container member function <code>erase()</code> to correct the endpoint of the container iterator after the remove operation [https://youtu.be/3J1Pz30IE4Q?t=9m51s 9:51]
+
* Removing items from a container, <code>std::remove</code> and <code>std::remove_if</code> [https://youtu.be/3J1Pz30IE4Q?t=6m11s 6:11]
* Introducing the Lambda function to replace custom functors [https://youtu.be/3J1Pz30IE4Q?t=11m51s 11:51] <br />- 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]
+
<div class="mw-collapsible-content">
* [WORK-IN-PROGRESS]
+
** Create a functor as a unary predicate for the <code>std::remove</code> function to remove elements using a threshold variable [https://youtu.be/3J1Pz30IE4Q?t=8m28s 8:28]
 +
** Use container member function <code>erase()</code> to correct the endpoint of the container after the remove operation [https://youtu.be/3J1Pz30IE4Q?t=9m51s 9:51]
 +
</div>
 +
* Introducing Lambda functions to replace custom functors [https://youtu.be/3J1Pz30IE4Q?t=11m51s 11:51]
 +
* Using the Lambda capture to bring in variables into the Lambda function [https://youtu.be/3J1Pz30IE4Q?t=13m34s 13:34]
 +
<div class="mw-collapsible-content">
 +
** Capture syntax explained: <code>[var]</code>,<code>[&var]</code>,<code>[=]</code>,<code>[&]</code>,<code>[newvar=var+10]</code>,<code>[this]</code>, capture multiple variables, mix&match capture modes
 +
** Stateful Lambdas; changing captured lambda variables using the <code>mutable</code> flag [https://youtu.be/3J1Pz30IE4Q?t=15m59s 15:59]
 +
</div>
 +
* 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]
 +
<div class="mw-collapsible-content">
 +
** Make it callable once: <code>[...](...){...}(vec.front());</code>, functor is destroyed immediately
 +
** 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>
 +
</div>
 +
* 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]
 +
* Introducing the Algorithm [[STD Gems]] series that takes a deep dive into its functionality [https://youtu.be/3J1Pz30IE4Q?t=19m20s 19:20]
 +
</div>
  
 
== Homework ==
 
== Homework ==
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* [http://www.planetchili.net/downloads/I16-HW.zip Source.cpp (homework file)]
 
* [http://www.planetchili.net/downloads/I16-HW.zip Source.cpp (homework file)]
 
* [https://github.com/planetchili/sprite Sprite Repo (for bonus problem)]
 
* [https://github.com/planetchili/sprite Sprite Repo (for bonus problem)]
 +
 +
The homework solution video can be found [https://youtu.be/_1-iES-Eytc here]
  
 
== Related Series ==
 
== Related Series ==

Revision as of 13:10, 27 June 2020

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]

In the homework solution there is a part where Chili uses an iterator into a stringstream [2]. This code no longer works due to changes (improvements) to the Visual Studio compiler. Basically, you cannot pass a temporary stream into the iterator constructor. See this: [3]

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: [var],[&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.

The homework solution video can be found here

Related Series

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

Links

Algorithms Library

See also