function parameters

[tanj at ucbvax.berkeley.edu]

I just spent an hour trying to figure out why my working program
suddenly stopped working.  Here's the culprit:

	    expand(*ptr++,*ptr++,*ptr++,ptr++,ptr++,ptr++);

(I'm working on a graphics project, which involves mapping surface
 textures to the surface of a torus {bagel}.  Expand takes a point
 and its norm and expands it to 16 more points by symmetry.)

After careful searching of K&R I found the reason;

	 The order of evaluation of arguments is undefined by the
	 language; take note that the various compilers differ.
							[p. 186]

The compiler I am using evaluates right to left.  If I were to number
the above arguments 1-6, when expand gets them they are 6-1.  I find
this contrary to my intuition.   Can anyone out there give me a good
reason as to why this is left up to compiler implementation?  And
if so is it generally true that evaluation of parameters is r-l?


			Sincerely,
				  Michael Berman
					(tanj at ucscc.BITNET)