item formatting in description list

Question

How can I get this to work:

\begin{description}
    \item[\texttt{foo :: a \rightarrow b}] bla
\end{description}

without having to write:

\begin{description}
    \item\ttfamily[foo~::~a~$\rightarrow$~b]\normalfont~bla
\end{description}

?

• \ttfamily: for typewriter formating
• ~: to get the spacing right(??)
• $: to activate math mode
• \normalfont: to get back to normal
• last ~: insert simple space(??)

or how would you list some function definitions and append a description for the functions?

Answer 1

How about

\begin{description}
    \item[\texttt{foo :: a $\rightarrow$ b}] bla
\end{description}

That is: add a closing brace and $s around \rightarrow.

Or maybe you want

\begin{description}
    \item[\texttt{[foo ::~a $\rightarrow$ b]}] bla
\end{description}

Answer 2

In this case I would \usepackage{enumitem}

And then write:

\begin{description}[font=\tt]
    \item[foo :: a $\rightarrow$ b] bla
\end{description}

This way you don't need to define the font for each of your items.

Answer 3

i notice you're missing a closing brace before the closing bracket, other than that the two seem to produce identical output for me, save the enclosing brackets in your second example.