Why does the following exponent fail in Fortran?

Asked Dec 12 '13 at 05:00

Active Dec 12 '13 at 08:39

Viewed 331 times

I am using Fortran 77, the g77 compiler.

I have the following.

program title
implicit none
real*4 x,y

y=2
x = (y-4)**.7

end program

However this doesn't seem to be working. If I do: -2^0.7 it works, but not if I do (-2)**.7. Why is that? I only ask because I am writing a program where y is a variable and it will go below 4, so I can't just write -2^0.7

Thanks!

edited Dec 12 '13 at 08:39

Sadiq Huq

asked Dec 12 '13 at 05:00

JXS832

3

Because you can't raise a negative number to a fractional power and still get a real number. – Joe Z Dec 12 '13 at 05:03
1

*so I can't just write* `-2^0.7`. Indeed not, that would not be Fortran. – High Performance Mark Dec 12 '13 at 09:12
1

Also, `-2**.7` does not equal `(-2)**.7` ;-) – Alexander Vogt Dec 12 '13 at 09:54
(y-4)*abs(y-4)**(.7-1) ?? what are you trying to do? – agentp Dec 13 '13 at 14:18

Why does the following exponent fail in Fortran?

0 Answers0