Precompiler flags ?

Hi,

I've been wondering if it is possible to use precompiler flags with FTN95, for example like this

#define keyword (some code) #ifdef keyword (some code) #endif

in order to be able to switch parts of the code easily on or off for compilation. I remember having seen these in a Fortran program by someone else and I have used them in C++. Is this possible with FTN95 too ?

Thanks Rainer

Rainer

Yes there are two ways to do this with FTN95.

You can use CIF or #ifdef. Both are described in the help file. Be careful if you are familiar with C and #ifdef etc because the behaviour in FTN95 is limited and slightly different. Work from very simple examples and then build up from this.

Hi Paul,

thanks for the help so far. But I've run into some problems. (I'm using FTN 95 v. 4.6.0.0.)

First, I tried the CIF family commands. The '/FPP' option was already checked in my compiler options, though I didn't specifically change any of the options. That was surprising, but not the actual problem. My source code looked like this:

PROGRAM mainprogram special parameter test /vparam test 1 ...

The line '/vparam test 1' got the error messages 'Invalid statement '/' at start of line' as well as 'Statement not recognized'. Replacing the line with '/sparam 1' had the same result. Without the '/', I simply get 'Statement not recognized'.

Then, I wanted to use the C style commands #ifdef, etc. I added '/cfpp' under 'Extra compiler options' and verified that the command was in the switches list. However, when compiling I got the message '/CFPP is not a valid option on the command line'. Without the option, naturally, any '#' symbol in the source code is flagged as an unknown symbol.

What also confuses me is that in the help file in the chapter 'C Style Conditional Compilation' the lines /VPARAM <name> <integer> /DEFINE <name> <integer> are described as 'command line switches'. I was thinking that command line switches were the additional options/switches given to the FTN95 executable, but these two lines were lines inside the source code.

Thanks for any advice. Rainer

Paul

There seems to have been a misunderstanding on my side as to how '/VPARAM' is used. Unfortunately, things are getting even more confusing. Let me explain.

From the FTN95 documentation:

'[big]Salford Conditional compilation[/big] FTN95 provides conditional compilation by means of the SPECIAL PARAMETER statement together with the /SPARAM and /VPARAM compile-time options and the CIF, CELSE and CENDIF statements.'

To me, 'compile-time option' could have meant either an option given to the compiler from the command line, that is a compiler switch. Or it could have meant a line of source code that is interpreted during compilation, before the actual source code. Because of what was stated in the documentation (see below), I understood it to be the latter. From what you are saying it seems to be the former.

The documentation continues:

'The specification statement SPECIAL PARAMETER <name> defines <name> to be of type integer. <name> must not appear in a type statement and is local to the program unit in which the SPECIAL PARAMETER statement appears. The value represented by <name> is set by means of the /SPARAM or /VPARAM compile-time option as follows: /SPARAM <integer> where <integer> is the required value.'

It seemed to me that 'SPECIAL PARAMETER <name>' was meant to be a line of source code. This also corresponds to the reference to 'program unit', which I assumed to be either the source files in the project (f95, inc, ...), or more likely the logical components, i.e. main program and modules. A compiler switch isn't local to any of these units. Hence, I assumed that the 'SPECIAL PARAMETER' line was meant to be in the source code. I further assumed it to be the declaration of the parameter, so it seemed logical that the assignment of a value to that parameter would come after the declaration and therefore also inside the source code. As I understood it, '/VPARAM' and '/SPARAM' are used to assign values to such special parameters. So, if '/VPARAM' is to be used as a compiler switch, what does 'SPECIAL PARAMETER' do and how is it used ?

Update:

I tried it with /VPARAM as a compiler switch and it works, with or without a 'SPECIAL PARAMETER' statement. Can it be that this statement is simply used to prevent other variables from having the same name as the special parameter ?

It also works without any /VPARAM switch. In this case, the special parameter checked with CIF apparently is assumed to be 0.

Rainer

Yes it looks like SPECIAL PARAMETER is not required in FTN95. It is throw back to FTN77. The parameter is used at pre-compile time so you will be able to use the same identifier for a different purpose in the compiled code.