Limiting range of variables when defining funxtions of several variables

*To*: mathgroup at smc.vnet.net*Subject*: [mg74676] Limiting range of variables when defining funxtions of several variables*From*: Michelasso <qzerty at gmail.com>*Date*: Sat, 31 Mar 2007 01:27:45 -0500 (EST)

Hello everybody, my problem is that I would like to plot a 3d graphic of a function of two variables, restricted to domain D={(x,y): x>= 0, y>=0, y <= 1-x}. I thought to define the function in this way: test[x_,y_/; y <= 1-x]:= x+y but this seems not to work, while it works for functions of one variable, i.e.: test2[x_/; x<= 1]:= 3x So, am I doing some syntax error, or is there some other kind of problems with my definition?