Add a section explaining operators

This should hopefully clear up some of the confusion about
runtime evaluation order of operators, and of their types.

2 files changed, 152 insertions, 1 deletions

diff --git a/.be/dcda61d1-5133-456a-b88c-6bf21e61777b/bugs/6ff0e3bf-8d9d-4329-ac36-f5e10b48535d/values b/.be/dcda61d1-5133-456a-b88c-6bf21e61777b/bugs/6ff0e3bf-8d9d-4329-ac36-f5e10b48535d/values
index 6e0bec6..29c9e04 100644
--- a/.be/dcda61d1-5133-456a-b88c-6bf21e61777b/bugs/6ff0e3bf-8d9d-4329-ac36-f5e10b48535d/values
+++ b/.be/dcda61d1-5133-456a-b88c-6bf21e61777b/bugs/6ff0e3bf-8d9d-4329-ac36-f5e10b48535d/values
@@ -26,7 +26,7 @@
 
 
 
-    "status": "open", 
+    "status": "fixed", 
 
 
 
diff --git a/introduction-to-python.tex b/introduction-to-python.tex
index 5747428..884542e 100644
--- a/introduction-to-python.tex
+++ b/introduction-to-python.tex
@@ -75,6 +75,152 @@ cadenas con 10 numeros
 \end{frame}
 
 
+\section{\en{Operators}\es{Operadores}}
+
+\en{So far, we've used several mathematical and string \emph{operators}.
+Operators in Python are very similar to those in mathematics: symbols which
+take one or two \emph{operands} (parameters or inputs) and evaluate to a single
+result. (Formally, they are unary or binary infix functions.)}
+\es{Hasta el momento, hemos utilizado varios \emph{operadores} matemáticos y de
+cadena. Los operadores en Python son muy similares a las de las matemáticas:
+símbolos que tienen uno o dos \emph{operandos} (parámetros o entradas) y
+evaluar a un solo resultado. (Formalmente, son funciones infijos unario o
+binario).}
+
+\en{As in mathematics, operators must be used with the correct number and type
+of operands. It wouldn't make sense to write $6 +$ as a sum, for example; or to
+write $15 8$ and expect to calculate the answer $15 + 8 = 23$.}
+\es{Al igual que en las matemáticas, los operadores deben ser utilizados con el
+número y el tipo correcto de operandos. No tendría sentido escribir $6 +$ como
+una suma, por ejemplo, o para escribir $15 8$ y esperar para calcular la
+respuesta $15 + 8 = 23$.}
+
+\en{When Python runs a program, operators are evaluated in order of precedence.
+For example, multiplication always takes precedence over addition, as in
+mathematics. Brackets can be used to enforce an ordering. During evaluation,
+Python effectively repeatedly replaces each operator and its operands with the
+result of the operation.}
+\es{Cuando Python se ejecuta un programa, los operadores se evalúan en el orden
+de precedencia. Por ejemplo, la multiplicación siempre tiene prioridad sobre la
+suma, como en matemáticas. Paréntesis pueden hacer cumplir una orden. Durante
+la evaluación, Python efectivamente reemplaza repetidamente cada operador y sus
+operandos con el resultado de la operación.}
+
+\begin{frame}[fragile]
+\frametitle{\en{Operator evaluation}\es{Evalución de operadors}}
+\begin{block}{\en{Integers}\es{Enteros}}
+\begin{lstlisting}[language=Python]
+15 * 7 + (6 / 2)
+== 105 + (6 / 2)
+== 105 + 3
+== 108
+\end{lstlisting}
+\end{block}
+\begin{block}{\en{Strings}\es{Cadenas}}
+\begin{lstlisting}[language=Python]
+'Soy %s' % ('Sr' + ' Gustavo' + ' Hernandez')
+== 'Soy %s' % ('Sr Gustavo' + ' Hernandez')
+== 'Soy %s' % 'Sr Gustavo Hernandez'
+== 'Soy Sr Gustavo Hernandez'
+\end{lstlisting}
+\end{block}
+\end{frame}
+
+\en{Here are the type signatures of a number of Python operators. These show
+how the operators should be used, with which types of variables, and what type
+of output they evaluate to. Note: Almost all integer types (\texttt{int}) below
+can be replaced with float. $\alpha$ represents any type. Assignment operators
+do not have a return value (so, for example, \texttt{5 == (a += 2)} is not
+valid Python.}
+\es{Aquí están las firmas de tipo de una serie de operadores de Python. Estos
+muestran cómo se deben utilizar los operadores, con el que los tipos de
+variables, y qué tipo de salida que evalúan. Nota: Casi todos los tipos de
+enteros (\texttt{int}) aquí pueden ser reemplazados con \texttt{float}.
+$\alpha$ representa cualquier tipo. Los operadores de asignación no tienen un
+valor de retorno (así, por ejemplo, \texttt{5 == (a + = 2)} no es válido
+Python.}
+
+\begin{frame}[fragile]
+\frametitle{\en{Operators}\es{Operadores}}
+\begin{block}{\en{Numerical}\es{Númerico}}
+\begin{align*}
+    \mathtt{int}\; \mathtt{+} \;\mathtt{int} &\to \mathtt{int} \\
+    \mathtt{int}\; \mathtt{-} \;\mathtt{int} &\to \mathtt{int} \\
+    \mathtt{int}\; \mathtt{*} \;\mathtt{int} &\to \mathtt{int} \\
+    \mathtt{int}\; \mathtt{/} \;\mathtt{int} &\to \mathtt{int} \\
+    \mathtt{int}\; \mathtt{\%} \;\mathtt{int} &\to \mathtt{int} \\
+    \mathtt{int}\; \mathtt{**} \;\mathtt{int} &\to \mathtt{int} \\
+    \mathtt{int}\; \mathtt{//} \;\mathtt{int} &\to \mathtt{int}
+\end{align*}
+\end{block}
+\end{frame}
+
+\begin{frame}[fragile]
+\frametitle{\en{Operators}\es{Operadores}}
+\begin{block}{\en{String}\es{Cadena}}
+\begin{align*}
+    \mathtt{str}\; \mathtt{+} \;\mathtt{str} &\to \mathtt{str} \\
+    \mathtt{str}\; \mathtt{\%} \;\mathtt{tuple} &\to \mathtt{str}
+\end{align*}
+\end{block}
+
+\begin{block}{\en{Comparison}\es{Comparación}}
+\begin{align*}
+    \mathtt{int}\; \mathtt{>} \;\mathtt{int} &\to \mathtt{bool} \\
+    \mathtt{int}\; \mathtt{<} \;\mathtt{int} &\to \mathtt{bool} \\
+    \mathtt{int}\; \mathtt{>=} \;\mathtt{int} &\to \mathtt{bool} \\
+    \mathtt{int}\; \mathtt{<=} \;\mathtt{int} &\to \mathtt{bool} \\
+    \alpha\; \mathtt{==} \;\alpha &\to \mathtt{bool} \\
+    \alpha\; \mathtt{!=} \;\alpha &\to \mathtt{bool}
+\end{align*}
+\end{block}
+\end{frame}
+
+\begin{frame}[fragile]
+\frametitle{\en{Operators}\es{Operadores}}
+\begin{block}{\en{Assignment}\es{Asignación}}
+\begin{align*}
+    \alpha\; &= \;\alpha \\
+    \mathtt{int}\; &\mathtt{+=} \;\mathtt{int} \\
+    \mathtt{int}\; &\mathtt{-=} \;\mathtt{int} \\
+    \mathtt{int}\; &\mathtt{*=} \;\mathtt{int} \\
+    \mathtt{int}\; &\mathtt{/=} \;\mathtt{int} \\
+    \mathtt{int}\; &\mathtt{\%=} \;\mathtt{int} \\
+    \mathtt{int}\; &\mathtt{**=} \;\mathtt{int} \\
+    \mathtt{int}\; &\mathtt{//=} \;\mathtt{int}
+\end{align*}
+\end{block}
+\end{frame}
+
+\begin{frame}[fragile]
+\frametitle{\en{Operators}\es{Operadores}}
+\begin{block}{\en{Logical}\es{Lógico}}
+\begin{align*}
+    \mathtt{bool}\; \mathtt{and} \;\mathtt{bool} &\to \mathtt{bool} \\
+    \mathtt{bool}\; \mathtt{or} \;\mathtt{bool} &\to \mathtt{bool} \\
+    \mathtt{not} \;\mathtt{bool} &\to \mathtt{bool}
+\end{align*}
+\end{block}
+
+\begin{block}{\en{Membership}\es{Afiliación}}
+\begin{align*}
+    \alpha\; \mathtt{in} \;\alpha~\mathtt{seq} &\to \mathtt{bool} \\
+    \alpha\; \mathtt{not~in} \;\alpha~\mathtt{seq} &\to \mathtt{bool}
+\end{align*}
+\end{block}
+\end{frame}
+
+\begin{frame}[fragile]
+\frametitle{\en{Operators}\es{Operadores}}
+\begin{block}{\en{Identity}\es{Identidad}}
+\begin{align*}
+    \alpha\; \mathtt{is} \;\alpha &\to \mathtt{bool} \\
+    \alpha\; \mathtt{is~not} \;\alpha &\to \mathtt{bool}
+\end{align*}
+\end{block}
+\end{frame}
+
+
 \section{Variables}
 
 \en{Python has \emph{variables} which allow results to be stored in memory so they
@@ -117,6 +263,11 @@ the user using the \texttt{raw\_input()} function.}
 \es{Variables son necesarios cuando se manipulan valores desconocidos, tales
 como los datos del usario introducida por la función \texttt{raw\_input()}.}
 
+\en{A single equals sign, \texttt{=}, is used to assign a value to a variable.
+It is called the \emph{assignment operator}.}
+\es{Un solo signo igual, \texttt{=}, se utiliza para asignar un valor a una
+variable. Se llama el \emph{operador de asignación}.}
+
 \begin{frame}[fragile]
 \frametitle{Variables}
 \begin{lstlisting}[language=Python,numbers=none]