[Tex/LaTex] logic symbol for counterfactuals

Question

I am looking for a symbol that looks like: []–>

So far I came up with $\Box\rightarrow$. The problem with this is, that the arrow is too far away from the box:

How could I achieve this so that the box is not so far away from the arrow?

Update:
Solution below.

Additionally I also needed a might counterfactual:

\newcommand{\counterfactualmight}{\ensuremath{%
\mathord{\Diamond}\kern-1.5pt
\raise0.5pt\hbox{$\mathord{\rightarrow}$}}}

Update 2:
Better Solution
From
http://www.ctan.org/pkg/comprehensive

%..
\usepackage{txfonts}
\usepackage{pxfonts}
%..
\begin{enumerate}
 \item A conditional: X $\rightarrow$ Y
 \item A strict conditional: X $\strictif$ Y
 \item A would-counterfactual conditional: X $\boxright$ Y
 \item A might-counterfactual conditional: X $\Diamondright$ Y
\end{enumerate}

Answer 1

A combination of \kern, \raise, \hbox, and \mathord (the final one to change the status of \rightarrow to "ordinary") should do the trick of aligning \Box and \rightarrow:

\documentclass{article}
\usepackage{amssymb}
\newcommand{\counterfactual}{\ensuremath{%
  \Box\kern-1.5pt
  \raise1pt\hbox{$\mathord{\rightarrow}$}}}
\begin{document}
$\Box\rightarrow$ vs.\ \counterfactual
\end{document}

---

Addendum: I don't know if you intend to use the \counterfactual macro in text or math mode. (That was also, by the way, why I used \ensuremath to encase the macro's contents.) If you intend to use it in math mode, it may be a good idea to give it "mathrel" (relational operator) status, e.g., by defining it as

\newcommand{\counterfactual}{\ensuremath{%
  \mathrel{\Box\kern-1.5pt\raise1pt\hbox{$\mathord{\rightarrow}$}}}}

That way, the spacing in expressions such as $A \counterfactual B$ will be correct without need for further fiddling.