Richard Donovan asked: > Is it possible to construct a J verb to test a number to be > irrational?
Not numerically. All values representable in a computer are rational, even those values which are the computer's closest (rational) approximations to irrational numbers. Put another way, if you had a magical verb irrat and you fed it the value 1p1 , how would it know you wanted the result 1 or 0 ? Both answers are reasonable. One is reasonable because pi is irrational, and 1p1 is the closest approximation to pi you could provide. Zero is reasonable because 1p1 is actually stored as 3.14159265358979323846 , which is clearly a rational number. How would irrat know your intention? (Did you want to know whether "3.14159265358979323846" is irrational, or whether "pi" is irrational, given that the two values are indistinguishable in double-precision floating point representation?) Now, a symbolic test is a different story. The symbol "pi" or a formula like 4*-/%1+2*i._ are distinguishable from values like 1p1. The question of whether it is possible to determine if a formula results in irrational number, I'll leave to the mathematicians. John Randall might know. -Dan ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
