convert fortran real to...

[Al]

I am about to start rewriting a fortran program to ansi C++.

Would it be best to convert the variables that are 'real' to float?
double? long double?

[Phlip]

Al wrote:

I am about to start rewriting a fortran program to ansi C++.

Step 1: use f2c, to translate Fortran source into complete C source that
compiles and runs. F2C is so stable that many use it as their Fortran
compiler. They never read the C intermediate.

Step 2: Read the C intermediate. It is not that bad, once you learn how
stereotypically it wraps all the Fortran nuances. But it won't be C++. Don't
ask it to be and you'l do fine. You can make minor tweaks to code in this
state.

Step 3: Write a billion unit tests that completely characterize this legacy
code. Many tests can pass sample data, collect sample results, and compare
them to golden references.

Step 4: Erase the source, and make each unit test pass by writing new
source.

Notice that at each step you can stop and have something useful to work
with.

--
Phlip
http://www.c2.com/cgi/wiki?ZeekLand

[Ioannis Vranos]

Al wrote:

I am about to start rewriting a fortran program to ansi C++.

Would it be best to convert the variables that are 'real' to float?
double? long double?

It depends on the precision that you want. I would begin with double.

--
Ioannis Vranos

http://www23.brinkster.com/noicys

[Chris Theis]

"Al" <al********@hotmail.com> wrote in message
news:11**********************@z14g2000cwz.googlegr oups.com...

I am about to start rewriting a fortran program to ansi C++.

Would it be best to convert the variables that are 'real' to float?
double? long double?

To be on the safe side I'd go with double.

Cheers
Chris

[beliavsky]

Chris Theis wrote:

"Al" <al********@hotmail.com> wrote in message
news:11**********************@z14g2000cwz.googlegr oups.com...

I am about to start rewriting a fortran program to ansi C++.

Would it be best to convert the variables that are 'real' to float?
double? long double?

To be on the safe side I'd go with double.

I agree, but let me note that most Fortran compilers on 32-bit
platforms use 4-byte reals, which corresponds to a C/C++ float. If the
Fortran programmer thought 8 byte variables were necessary, he would
have declared them as DOUBLE PRECISION or the nonstandard, but common,
REAL*8. Many Fortran compilers have an option to "promote" REAL
variables to double precision. If one has a make file or build script
showing that this option was used, then the corresponding C++ variables
should be double.

[red floyd]

Chris Theis wrote:

"Al" <al********@hotmail.com> wrote in message
news:11**********************@z14g2000cwz.googlegr oups.com...

I am about to start rewriting a fortran program to ansi C++.

Would it be best to convert the variables that are 'real' to float?
double? long double?

To be on the safe side I'd go with double.

Actually, if you're lucky, then they're already declared in fortran as
either
REAL*4 or REAL*8, in which case the decision for float or double is made
for you. Otherwise, I'd agree with Chris and go with double.

It's been ages since I did FORTRAN (back in the ancient WATFOR/WATFIV
days), but didn't it also have an explicit DOUBLE PRECISION declaration?