unusual IF statement processing in XLFortran under AIX

[eggsauce]

I am using XL Fortran v7.1.1.2 under AIX 5.1 and have some unusual behaviour inside an if statement.

I have discovered that the following fortran IF statement does not work the way it appears to read
(code in the if block is NEVER executed):

if ((someFunction(someArg) .eqv. .true. &
.or. someParameter >= 2)) then

The syntax that works is:
if ((someFunction(someArg) .eqv. .true. ) &
.or. someParameter >= 2) then

Note the different bracket positioning.

The syntax details do not clearly explain why the first statement does not work. I have speculated that perhaps the logical expression is being converted into an arithmetic due to the presence of the brackets but other than that it is a bit of a mystery.

Has anyone else also observed this behaviour or have an alternative explanation?

thanks in advance
John

 

[xwb]

It is basically operator precedence. The order is

.not.
.and.
.or.
.eqv. or .neqv.

if you have

a .and. b .or. c

by default, the grouping is

(a .and. b) .or. c

Similarly if you have

a .eqv. b .or. c

the grouping is

a .eqv. (b .or. c)

When in doubt, put in brackets. Anyway testing for .eqv. .true. is a waste of time. It is simpler if you have

if (someFunction(someArg) .or. someParameter .ge. 2)