a short code for creating a random (1,-1) matrix

I have no idea whether this is the first one, but I am pretty sure that you guys can fully understand what can be done by this short and concise matlab code, that is, to generate a random matrix of any given order, with entries randomly chosen from {1,-1}. In fact, the code can be extended to produce any random matrix whose elements are randomly chosen from any dyadic set ,say, {a,b}. The work was originated and inspired by the blog of Terence Tao on random matrix (see the webpage:
http://terrytao.wordpress.com/tag/random-matrices/)
and a talk "Discrete random matrices " by P.M.Wood from Stanford on the BADMath day of Spring 2010, San Jose,CA.
The running of the code is very fast, as you can find. But it will sharply slow down and display "inf" on your command window if you
put "det" function involved to test its singularity. Sure we may avoid this by using instead a logic function.