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\documentclass[14pt,compress,aspectratio=169]{beamer}
\input{macros.tex}
\title[Closures]{Advanced Python}
\subtitle{Closures}
\author[FOSSEE] {The FOSSEE Group}
\institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}
\date[] {Mumbai, India}
\begin{document}
\begin{frame}
\titlepage
\end{frame}
\begin{frame}
\frametitle{Overview}
\begin{itemize}
\item Higher-order functions
\item Closures
\end{itemize}
\end{frame}
\begin{frame}[fragile]
\frametitle{Recap of higher-order functions}
\begin{lstlisting}
In []: def sqr(x):
...: return x*x
In []: def sum(func, n):
...: result = 0
...: for i in range(n):
...: result += func(n)
...: return result
In []: sum(sqr, 5)
Out[]: 125
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{Recap of higher-order functions}
\begin{lstlisting}
def f():
def g(x):
return x+1
return g
In []: func = f()
In []: func(1)
In []: f()(1) # Also valid!
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{Closures}
\begin{lstlisting}
def mul(x):
def g(y):
return y*x
return g
In []: twice = mul(2.0)
In []: twice(20)
Out[]: 40.0
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{Closures ...}
\begin{lstlisting}
In []: twice = mul(3.0)
In []: twice(20)
Out[]: 60.0
\end{lstlisting}
\end{frame}
\begin{frame}
\frametitle{Discussion}
\begin{itemize}
\item \typ{g} uses \typ{x}
\item \typ{x} is different in each case
\item So \typ{twice, thrice} ``curry'' the passed \typ{x}
\item This function is called a closure
\item Encloses its local environment
\end{itemize}
\end{frame}
\begin{frame}[fragile]
\frametitle{Higher-order functions}
\begin{itemize}
\item Functions that manipulate functions
\item Passing a function as an argument
\item A function that returns another function
\item A closure
\end{itemize}
\end{frame}
\end{document}
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