Sun WorkShop[tm] 6 update 2: Fortran Pre-Processor fpp Readme
Source code preprocessors have long been used to provide these capabilities. They allow the user to insert directive statements within the source code that effect the output of the preprocessor.
Typically, these special directives may appear as comment lines to a compiler. In general, source code preprocessors permit the user to define special variables and logical constructs that conditionally control which source lines in the file are passed on to the compiler and which lines are skipped over. In addition, the preprocessor's source line editing capabilities allow the user to specify how the source code should be changed according to the value of defined string variables.
Historically, the source code preprocessor found in standard C compilers, cpp, has been used to provide Fortran programmers with these capabilities. However, cpp is too closely tied into the C language syntax and source line format to be used without careful scrutiny. The proposed Fortran PreProcessor, fpp, would provide Fortran-specific source code capabilities that C programmers have come to expect in UNIX environments.
Some of fpp's capabilities could, potentially, be reapplied in other tools. An implementation of fpp would have to parse and analyze Fortran source, evaluate Fortran expressions and generate Fortran output. These are the building blocks that other tools would need to provide an enriched environment for Fortran program development.
The following section describes the capabilities of fpp in more
detail. For full details, see the
fpp(1) man page.
Preprocessor directives may appear inside Fortran comments. The preprocessor will also modify the text inside a Fortran comment.
The preprocessor will operate on both fixed and free form source. Fixed form source files would have the extension .F while free form source files would have the extension .F90. Note that the fixed form file name convention applies to both FORTRAN 77 and Fortran 90. Files with such extensions will be preprocessed first before the appropriate compiler is invoked.
If the expansion of a macro or string replacement causes the column width of a line to exceed column 72 (for fixed form) or column 132 (for free form), the preprocessor will generate the appropriate continuation lines.
defines the value of the variable "name" to be "string", with the result that every occurrence of the token "name" [outside of IMPLICIT statement bounds, text in FORMAT statements and string literals] is literally replaced by "string".#define name string
Note: In case of IMPLICIT statement bounds and text in FORMAT statements, macros are not expanded only in case of conflict with valid literals in that context.
"Macro"-like, inline replacements with arguments are also
Examples:#define name (arg1 [,arg2]...) string-with-args-inserted
Preprocessor variables are enabled from the point of definition upto the end of the compilation unit. (i.e. global scoping across the file)#define SOLARIS_2 .TRUE. #define CONVERT(TO_FARENHEIT) ((TO_FARENHEIT*9)/5)+32
Preprocessor variables can be explicitly undefined using
or#if condition1 block1 [#elif condition2 block2 ] ... [#else blockn ] #endif
The conditions are fpp expressions involving preprocessor variables (specified by #define statements). Note that the conditions may be specified within parentheses. These fpp expressions are a superset of cpp expressions in that they can evaluate Fortran logical literals. So, .TRUE. is valid in an fpp expression. The preprocessor evaluates these conditions to get a true or false result. The expressions may not evaluate floating point values or include intrinsic functions.#ifdef name block #endif #ifndef name block #endif
#define SOLARIS_2 .TRUE. #if (SOLARIS_2) CALL solaris_2 (X,Y,Z) #else CALL solaris_1 (X,Y,Z) #endif
Nesting of #include is permitted. #include statement may not appear in a continued line (i.e. the first statement in an included file may not be a continuation line)#include filename
Define name as 1. This is the same as if a #define name1 line appeared in the source file that fpp is processing.
This is the same as if a #define name def line appeared in the source file that fpp is processing.
Insert 'directory' into the search path for #include files with names not beginning with '/'. 'directory' is inserted ahead of the standard list of 'include' directories. So, #include files with names enclosed in double-quotes (") are searched first in the directory of the file with the #include line, then in directories named with the -I options, and lastly, in the directories from the standard list.
Remove any initial definition of 'name', where 'name' is predefined by the preprocessor.
Use 'directory' in place of the standard list of directories when searching for #include files.