Finished C++ and basic examples

* Ready to talk!

Notes.md

@@ -52,19 +52,19 @@ html header:    <link rel="stylesheet"
        ```
    + currying: not really, but binding via lambdas or functools.partial() or
                https://mtomassoli.wordpress.com/2012/03/18/currying-in-python/
-   - decorators!
+   + decorators!
-   - still FP has advantages and is heavily used, i.e. in genomics (works on
+   + still FP has advantages and is heavily used, i.e. in genomics (works on
      tons of lengthy lists)
- * FunCtional++: On the fast lane
+ * FunC++tional: On the fast lane
-   - "Classical" C++ has some functional stuff, bust i.e. no lambdas (hardly usable)
+   + "Classical" C++ has some functional stuff, bust i.e. no lambdas (hardly usable)
-   - Changed with the new C++11-standard
+   + Changed with the new C++11-standard
-   - Buzzwords:
+   + Buzzwords:
-      - `map` defines a Datatype in C++!
+      + `map` defines a Datatype in C++!
-      - lambdas in C++
+      + lambdas in C++
         ```[](int x, int y) { return a<b;} ;```
         [] can be used to capture variables, i.e. by reference or value
-      - `std::for_each` from `algorithm`: Apply `void fun(T &a)` to iterator
+      + `std::for_each` from `algorithm`: Apply `void fun(T &a)` to iterator
         containing `T` values
-      - `std::transform` from `algorithm`: same as for_each, but stores return
+      + `std::transform` from `algorithm`: same as for_each, but stores return
         value in another range
-      - `std::accumulate` from `numeric`: Wants binary operation, i.e. `std::minus<int>`
+      + `std::accumulate` from `numeric`: Wants binary operation, i.e. `std::minus<int>`

examples/02_python.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python3
+import sys
+
+
+def debug(func):
+    def inner(*args, **kwargs):
+        sys.stderr.write("F: {}, args: {}, kwargs: {}\n"
+                         .format(func.__name__, args, kwargs))
+        return func(*args, **kwargs)
+    return inner
+
+
+@debug
+def foo(x):
+    pass
+
+
+def mybubblesort(array, func=lambda x, y: True if x > y else False):
+    if (len(array) == 0):
+        return []
+    else:
+        x, *xs = array
+        return mybubblesort([y for y in xs if func(x, y)], func) \
+            + [x] \
+            + mybubblesort([y for y in xs if not func(x, y)], func)
+
+if __name__ == "__main__":
+    foo(2)
+    a = [2,5,12,4,1,0]
+    print(mybubblesort(a))
+    print(mybubblesort(a, lambda x, y: True if x < y else False))

examples/03_cpp.cpp

@@ -0,0 +1,50 @@
+#include <iostream>
+#include <vector>
+#include <algorithm>
+#include <numeric>
+
+int main() {
+  std::vector<int> a{1,2,3,4};
+  std::vector<int> b{5,6,7,8};
+  // result vector
+  std::vector<double> c(a.size(), 0);
+
+  // double
+  std::for_each(a.begin(), a.end(), [](int &n){ n*=2;});
+  
+  std::cout << "Double:" << std::endl;
+  for (auto const &i: a){ std::cout<<i<<" ";}
+  std::cout << std::endl;
+
+  // Reset a
+  a = {1,2,3,4};
+  
+  // inverse
+  std::transform(a.begin(), a.end(),
+                 c.begin(),
+                 [](int i){return 1.0/i;});
+
+  std::cout << "Multiplicative inverse:" << std::endl;
+  for (auto const &i: c){ std::cout << i << " ";}
+  std::cout << std::endl;
+
+  // reziprocal sum
+  std::transform(a.begin(), a.end(),
+                 b.begin(), c.begin(),
+                 [](int i, int j){return 1.0/(1.0/i + 1.0/j);});
+  std::cout << "Reziprocal sum:" << std::endl;
+  for (auto const &i: c){ std::cout << i << " ";}
+  std::cout << std::endl;
+
+  // Folds
+  int sum = std::accumulate(a.begin(), a.end(), 0);
+  int diff = std::accumulate(a.begin(), a.end(), 15, std::minus<int>());
+  int mult = std::accumulate(a.begin(), a.end(), 1,
+                             [](int a, int b)->int { return a * b; });
+  std::cout << "Sum: " << sum
+            << "\nDiff from 15: " << diff
+            << "\nProd: " << mult
+            << std::endl;
+  
+  return 0;
+}

examples/04_cpp17.cpp

@@ -0,0 +1,32 @@
+#include <iostream>
+// compile using std=c++1z-option
+// tested with clang++ and g++
+// using:
+// $CC -Wall -Werror -pedantic -pedantic-errors -std=c++1z -o $OUT $IN
+
+/* "Old" code:
+ * The usage of auto to implicitly get the return type is C++17,
+ * the main part is using C++11 variadic templates and overloading
+ */
+auto sum1() { return 0;}
+
+template<typename T>
+auto sum1(T t) { return t; }
+
+template<typename T, typename... Ts>
+auto sum1(T t, Ts... ts) {return t + sum1(ts...);}
+
+/* New code:
+ * Using c++17 fold expressions, this gets way shorter and
+ * less error prone
+ */
+template <typename... T >
+auto sum2 (T... args){
+  return (... + args);
+}
+
+int main() {
+  std::cout << sum1(1,2,3,4,5,6,7,8,9,10) << std::endl;
+  std::cout << sum2(1,2,3,4,5,6,7,8,9,10) << std::endl;
+  return 0;
+}

tex/headers/listings.tex

@@ -3,6 +3,8 @@
 \usepackage{upquote}
 \usepackage[section, cache=true,]{minted}
 
+\usemintedstyle{manni}
+
 \newminted[ccode]{c}%
 {
   linenos=true,
@@ -58,5 +60,5 @@
 
 %%% Local Variables:
 %%% mode: latex
-%%% TeX-master: "../linux-script"
+%%% TeX-master: "../wtfunctional"
 %%% End:

tex/wtf.bib

@@ -1,11 +1,29 @@
 @online{whichfold,
-title={Foldr Foldl Foldl' - HaskellWiki},
+title = {Foldr Foldl Foldl' - HaskellWiki},
-urldate={2016-04-21},
+url = {wiki.haskell.org/Foldr_Foldl_Foldl},
-url={https://wiki.haskell.org/Foldr_Foldl_Foldl%27},
 }
 
 @online{decorators,
-title={simeonfranklin.com - Understanding Python Decorators in 12 Easy Steps!},
+title = {simeonfranklin.com - Understanding Python Decorators in 12 Easy Steps!},
-urldate={2016-04-25},
+url = {simeonfranklin.com/blog/2012/jul/1/python-decorators-in-12-steps/},
-url={http://simeonfranklin.com/blog/2012/jul/1/python-decorators-in-12-steps/},
+}
+
+@Online{cppiter,
+title = {C++ concepts: Iterator - cppreference.com},
+url = {en.cppreference.com/w/cpp/concept/Iterator},
+}
+
+@online{generics,
+title = {Index of /~kami/2015-32C3/},
+url = {people.freebsd.org/~kami/2015-32C3/},
+}
+
+@online{cpp17,
+title = {C++17 content prediction (pre-Jacksonville and post-Kona report) – Michael Wong's Standard},
+url = {https://wongmichael.com/2016/02/28/c17-content-predictionpre-jacksonville-and-post-kona-report/},
+}
+
+@online{cppfolds,
+title = {Fold expressions},
+url = {www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4191.html},
 }

tex/wtfunctional.tex

@@ -5,15 +5,17 @@
 \usepackage{tabularx}
 \usepackage[backend=biber,]{biblatex}
 \bibliography{wtf}
+\renewcommand{\bibfont}{\small}
 
 \usepackage{fontspec}
 \setsansfont{Fira Sans}
 \setmonofont{Inconsolata-g}
 
 \usetheme{Antibes}
-%\usecolortheme{beaver}
 \setbeamercovered{transparent}
 
+\newcommand{\cpp}{\texttt{C++}}
+
 \title{WTFunctional}
 \author{Oliver Rümpelein}
 \subtitle{Using functional structures in non-functional languages}
@@ -23,6 +25,17 @@
 \begin{document}
 \frame{\titlepage}
 
+\begin{frame}[plain]{What?}
+    \begin{enumerate}[<+->]
+    \item Dafunc? Introduction to functional paradigms using Haskell
+    \item PhuncY! Functional programming in Python
+    \item Fun\cpp{}tional: STL-hacks and usage in \cpp
+    \end{enumerate}
+    \begin{uncoverenv}<4-| invisible@1-3>
+        \emph{With preview to \cpp{}17/20/22!}
+    \end{uncoverenv}
+\end{frame}
+
 \section{Dafunc?}
 \subsection{Functional programming}
 \begin{frame}{Understanding functional paradigms}
@@ -169,7 +182,7 @@ c = addto b 4
 \end{frame}
 
 \begin{frame}[fragile]{Folds (2)}
-    \uncover<+-> Example: Self written Right fold and sum:
+    \uncover<+-> Example: Self written right fold and sum:
 \begin{haskell}
 mfold f z [] = z
 mfold f z (x:xs) = f x (mfold f z xs)
@@ -185,9 +198,9 @@ g = msum [1..100]
     Get all Pythagorean triangles with a hypotenuse off length at most 15:
 \begin{haskell}
 > [(a,b,c) | a <- [1..15],
-b <- [1..a],
+             b <- [1..a],
-c <- [1..b],
+             c <- [1..b],
-a^2 == b^2 + c^2]
+             a^2 == b^2 + c^2]
 [(5,4,3),(10,8,6),(13,12,5),(15,12,9)]
 \end{haskell}
 \end{frame}
@@ -197,8 +210,8 @@ a^2 == b^2 + c^2]
 \begin{haskell}
 bsort f [] = []
 bsort f (x:xs) = (bsort f a) ++ [x] ++ (bsort f b)
-where a = [ y | y <- xs, not (f x y) ]
+  where a = [ y | y <- xs, not (f x y) ]
-b = [ y | y <- xs, (f x y) ]
+        b = [ y | y <- xs, (f x y) ]
 mbsort = bsort (\x y -> (x > y))
 \end{haskell}
     \pause Result:
@@ -209,7 +222,7 @@ mbsort = bsort (\x y -> (x > y))
 \end{haskell}
 \end{frame}
 
-\section{Phuncy!}
+\section{PhuncY!}
 \subsection{Overview}
 \begin{frame}{Functional programming in Python}
     \begin{itemize}[<+->]
@@ -222,6 +235,7 @@ mbsort = bsort (\x y -> (x > y))
     \end{itemize}
 \end{frame}
 
+\subsection{Elements}
 \begin{frame}[fragile]{Lambdas, Maps}
     \begin{itemize}[<+->]
     \item Lambda-syntax: \pycmd{lambda a,b: a+b}
@@ -286,27 +300,233 @@ bar(3) # 5
     \end{itemize}
 \end{frame}
 
-\begin{frame}[fragile]{Decorators}
+\begin{frame}{Decorators (1)}
     \begin{itemize}[<+->]
     \item Often used to modify functions in Frameworks
-    \item Encapsulates other functions. More infos at \cite{decorators}
+    \item Basic pattern: Decorator is a function that itself takes a function,
+        and returns a wrapper
+    \item Step-by-step introduction to decorators at~\cite{decorators}
+    \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Decorators (2)}
 \begin{pycode}
 def debug(func):
   def inner(*args, **kwargs):
-    sys.stderr.write("F: {}, args: {}, kwargs {}".format(func.__name__, args,
+    print("F: {}, args: {}, kwargs: {}\n"
-    kwargs))
+          .format(func.__name__, args, kwargs))
-    return func(*args, **args)
+    return func(*args, **kwargs)
   return inner
+
 @debug
 def foo(x):
-  print(x)
+  pass
+
+foo(2) # => F: foo, args: (2), kwargs: {}
 \end{pycode}
+\end{frame}
+
+\subsection{Conclusion}
+\begin{frame}{Quite enough…}
+    \begin{itemize}[<+->]
+    \item Python is not really functional…
+    \item …but is strongly influenced by functional paradigms.
+    \item Its functional parts are heavily used, i.e in Genomics
     \end{itemize}
 \end{frame}
 
+\begin{frame}[fragile]{Example}
+\begin{pycode}
+def mybubblesort(array,
+      func=lambda x, y: True if x > y else False):
+  if (len(array) == 0):
+    return []
+  else:
+    x, *xs = array
+    return mybubblesort([y for y in xs
+                         if func(x,y)], func) \
+        + [x] \
+        + mybubblesort([y for y in xs \
+                         if not func(x,y)], func)
+\end{pycode}
+\end{frame}
+
+\section{Fun\cpp{}ional}
+\subsection{Overview}
+
+\begin{frame}{Functional programming in \cpp{}}
+    \begin{itemize}[<+->]
+    \item \enquote{Classical} \cpp{} has a few functional elements…
+    \item …but lacks lambdas, for instance.
+    \item This changed with the modern standards, starting from \cpp{}11.
+    \end{itemize}
+\end{frame}
+
+
+\subsection{Elements}
+\begin{frame}[fragile]{Lists}
+    \begin{itemize}[<+->]
+    \item In \cpp{}, \emph{Iterators} are equivalent to lists in functional languages.
+    \item Examples of iterators include \cppcmd{vector} and \cppcmd{array}.
+    \item See~\cite{cppiter} for more information about the specific iterator
+        types and the prerequisites they bring.
+    \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{lambdas}
+    \begin{itemize}[<+->]
+    \item \emph{Lambdas} have been introduced with \cpp{}11
+    \item Syntax:
+\begin{cppcode}
+[v1,&v2](int v1, int v2)
+    {return v1 < v2}
+\end{cppcode}
+    \item The \cppcmd{[]} denotes the capture-list and specifies, whether
+        variables are used by value or by reference. If this is empty,
+        anything is used by value.
+    \item Lambdas are fully-featured \emph{functionals}, such are functions
+        wrapped with \cppcmd{std::function}, and objects implementing
+        \cppcmd{operator()}.
+    \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Maps (1)}
+    \uncover<+->{\begin{alertblock}{map ≠ map}
+          \cppcmd{std::map} is a data-type similar to pythons \pycmd{dict} and has no
+          relation to the functional concept of maps!
+      \end{alertblock}}
+    \uncover<+->{The following can be used instead (both from \cppcmd{<algorithm>}):}
+    \begin{itemize}[<+->]
+    \item \cppcmd{std::for_each}
+    \item \cppcmd{std::transform}
+    \end{itemize}
+\uncover<+->{But they are quite different.}
+\end{frame}
+
+\begin{frame}[fragile]{Maps (2)}
+    \uncover<+->{\cppcmd{std::for_each} applies a function \cppcmd{void fun(T &a)} to elements
+      of an iterator containing values of type \cppcmd{T} in place:}
+    
+    \begin{uncoverenv}<+->
+\begin{cppcode}
+vector<int> a{1,2,3};
+for_each(a.begin(), a.end(), 
+         [](int &n){ n*=2; });
+\end{cppcode}
+    \end{uncoverenv}
+    
+    \uncover<+->{This multiplies each element in \cppcmd{a} by 2.}
+\end{frame}
+
+\begin{frame}[fragile]{Maps (3)}
+    \uncover<+->{In contrast, \cppcmd{std::transform} returns a new iterator containing type
+\cppcmd{U}. Thus, the function has to be \cppcmd{U func(T val)}:}
+
+\begin{uncoverenv}<+->
+\begin{cppcode}
+vector<int> b{1,2,3,4};
+vector<double> c(b.size(), 0.0);
+transform(b.begin(), b.end(), c.begin(),
+          [](int i){ return 1.0/i; });
+\end{cppcode}
+\end{uncoverenv}
+
+\uncover<+->{This gives a vector c filled with the inverse elements of b.}
+\uncover<+->{There are also forms of \cppcmd{transform} that merge two
+  iterators (see examples in git-repo).}
+\end{frame}
+
+\begin{frame}[fragile]{Filters}
+    \begin{itemize}[<+->]
+    \item This is ugly
+    \item No syntactic sugar as with python's list comprehensions
+    \item Use \cppcmd{std::remove_if} or \cppcmd{std::remove_copy_if} from \cppcmd{<algorithm>},
+    \item afterwards \cppcmd{transform}.
+    \item Or make use of the \cppcmd{boost::filter_iterator} library.
+    \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Folds}
+    \begin{itemize}[<+->]
+    \item \cppcmd{std::accumulate} is defined in \cppcmd{<numeric>}
+    \item Takes bounds of an Iterator, and a \cppcmd{BinaryOperation}
+    \item Example:
+\begin{cppcode}
+vector<int> a{1,2,3,4}
+int b = accumulate(a.begin(), a.end(), 0); // sum
+int c = accumulate(a.begin(), a.end(), 15, minus<int>());
+\end{cppcode}
+        \cppcmd{std::minus<int>} is defined in \cppcmd{<numeric>} as well.
+    \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Generics and \texttt{D}}
+\begin{itemize}[<+->]
+    \item These are only procedural examples of functional programming.
+    \item Much can be done using \emph{generic} techniques
+        (\enquote{templates}).
+    \item Many examples: \cite{generics}
+    \item Much more to come in \cpp{}20/22 (\cite[What will Not make it into
+        C+17,…]{cpp17})
+        \begin{itemize}[<+->]
+        \item \emph{Concepts} are kind of constraints on template parameters.
+        \item \emph{Ranges} will replace iterators
+        \item All of the above and more are available in the \texttt{D}
+            programming language! (\url{dlang.org})
+        \end{itemize}
+    \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Generics example: Folds}
+    \begin{uncoverenv}<+->
+        Using \cpp{}11 with variadic templates, one has (mod \cppcmd{auto})
+\begin{cppcode}
+auto sum() { return 0; }
+
+template<typename T>
+auto sum(T t) { return t; }
+
+template<typename T, typename... Ts>
+auto sum(T t, Ts... ts) { return t + sum(ts...); }
+\end{cppcode}
+    \end{uncoverenv}
+    \begin{uncoverenv}<+->
+        With new folding expression (\cite{cppfolds}):
+\begin{cppcode}
+template<typename T>
+auto sum(const auto&... args)
+   { return (args + ...); }
+\end{cppcode}
+    \end{uncoverenv}
+\end{frame}
+
 \begin{frame}[plain]{References}
     \printbibliography
 \end{frame}
+
+\section{The}
+\subsection{end}
+
+\begin{frame}[plain]{Thanks for listening!}{Any questions?}
+    \href{https://git.f3l.de/pheerai/wtfunctional/}{Git-Repo with examples and
+      slides}: \url{git.f3l.de/pheerai/wtfunctional/}
+    
+    \begin{description}
+    \item[Mail:] \url{oli_r@fg4f.de}
+    \item[XMPP:] \url{pheerai@im.f3l.de}
+    \item[Github:] \href{https://github.com/pheerai/}{pheerai}
+    \item[Misc:] Signal, Telegram,…
+    \item[…or] later having some drink
+    \end{description}
+    \vfill
+    \tiny \raggedleft Proudly typed using Lua\LaTeX{}. Slides-theme: \emph{Antibes}\\
+    Fonts used are \href{github.com/mozilla/Fira}{\emph{Fira Sans}} and
+    \href{leonardo-m.livejournal.com/77079.html}{\emph{Inconsolata G}}.\\
+    Syntax and code highlighting with
+    \href{https://github.com/gpoore/minted}{\emph{minted}} and
+    \href{http://pygments.org}{\emph{pygments}}.
+\end{frame}
+
 \end{document}
 
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