| F language | |
| Developer: | The Fortran Company |
| Paradigm: | Array, procedural, modular |
| Typing: | static, manifest |
| Influenced By: | Fortran 95 |
F is a modular, compiled, numeric programming language, designed for scientific programming and scientific computation.[1] F was developed as a modern Fortran, thus making it a subset of Fortran 95.[2] It combines both numerical and data abstraction features from these languages. F is also backwards compatible with Fortran 77, allowing calls to Fortran 77 programs. F was implemented on top of compilers from NAG, Fujitsu, Salford Software and Absoft. It was later included in the g95 compiler.
F is designed to be a minimal subset of Fortran, with only about one hundred intrinsic procedures.[3] Language keywords and intrinsic function names are reserved keywords in F and no other names may take this exact form. F contains the same character set used in Fortran 90/95 with a limit of 132 characters. Reserved words are always written in lowercase. Any uppercase letter may appear in a character constant. Variable names do not have restriction and can include upper and lowercase characters.
F supports many of the standard operators used in Fortran. The operators supported by F are:
+, -, *, /, **<, <=, ==, /=, >, >=.not., .and., .or., .eqv., .neqv.//The assignment operator is denoted by the equal sign =. In addition, pointer assignment is denoted by =>. Comments are denoted by the ! symbol:
Similar to Fortran, the type specification is made up of a type, a list of attributes for the declared variables, and the variable list.[2] F provides the same types as Fortran, except that double precision floating point variables must be declared as real with a kind with a kind parameter:
F does not have intrinsic support for object-oriented programming, but it does allow for records:[2]
Variable declarations are followed by an attribute list. The attributes allowed are parameter, public, private, allocatable, dimension, intent, optional, [[pointer (computer programming)|pointer]], save and target. The attribute list is followed by ::, which is part of the syntax. F also allows for optional initialization in the list of objects. All items in a list will have the same attributes in a given type declaration statement. In addition, declarations are attribute oriented instead of entity oriented.
F supports 3 statements for control flow: if, a basic conditional, case, a switch statement, and do, a conditional while loop. The return, stop, cycle, and exit statements from Fortran may be used to break control flow.
do i = 100 x = x+i print*,i cycleend do
max : do if (x > y) then exit max end if x = yend do maxstop
if (x < y) then x = x + yelse if (x > y) then x = y - xend if
select case (maximum): case (0) x = 0 case (1) x = 1 case (5) x = 5 case default x = 10end select
F places a heavy emphasis on modular programming.
Placing procedures outside of a module is prohibited. F supports most of the functions and subroutines found in the Fortran 95 standard library. All functions in F are external by default and require a result clause that returns the value of a function.[2] F supports recursion.
All of the intrinsic procedures found in Fortran 95 may be used in F, with the exceptions of achar, iachar, lge, lgt, lle, llt, transfer, dble, dim, dprod, and mod.