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# read number in if sentences

## read number in if sentences

(OP)
Hallo everybody,

I have this file:

parameter=5

If (a==(parameter))
write(2,*)b
end if

where parameter it will be used for differents cases but the problem is that seems to be: If (a==(parameter)).It seems that can not read the number that I give two lines before.

Thanks
Albert

### RE: read number in if sentences

that syntax is wrong; Fortran generally doesn't use
two equal signs "==" for that purpose.

### RE: read number in if sentences

(OP)
prost,
if I put a number is working:

parameter=5

If (a==(5))
write(2,*)b
end if

but not if I put:
If (a==(parameter))

### RE: read number in if sentences

By default both parameter and a are real floating point numbers. It is considered bad fortran practice to compare two real numbers for equality, since you are relying too much on the precision of the hardware and software. Variable a may be stored as 5.0000001 and parameter may be stored as 4.99999999

Also 5 on its own is considered to be an integer, you should use 5.0 for single precision or 5.0D0 for double precision.

### RE: read number in if sentences

And in the dear dead days beyond recall "==" was .EQ.

### RE: read number in if sentences

I still use .EQ.  !

### RE: read number in if sentences

(OP)
johnhors,

It still doesn't work even If I define parameter and a as integer or as real.

### RE: read number in if sentences

(OP)
If I use:

If (a==(parameter))

it says "user breakpoint called from code 0x7c901230".

### RE: read number in if sentences

what level of Fortran did they introduce "=="? I too still use .EQ.

### RE: read number in if sentences

Try using something else other than parameter.  parameter is a keyword; not a reserved word: just a keyword.  It is recognized as part of the syntax and you are allowed to use it but it can be confusing and some compilers may not like it.

In Fortran, if you don't declare a variable, and it begins with letters a-h, o-z, it is real.  Real, real comparisons don't always work.

#### CODE

prorgram main
integer:: param, a, b
param = 5

if (a .eq. param) then
write(2,*)b
end if
stop
end

### RE: read number in if sentences

(OP)
Thanks to everybody now is working!

### RE: read number in if sentences

The relief is palpable...

.EQ. rules ok...

### RE: read number in if sentences

(OP)
ehehehe thanks again

### RE: read number in if sentences

I think you all will find that "=="  is nowadays much more commonly used than ".EQ.".   I'd venture that this has been true for more than 10 years now for those working with Fortran90 or beyond.

Also...  the above code now works due to the use of the variable PARAM.  The symbol used to check for equality is irrelevant.

Dan
dan@dtware.com

### RE: read number in if sentences

Never.

The sky is falling...

"==" in FORTRAN.

Doomed, I tell ye, doomed.

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