F is designed to be a minimal subset of Fortran, with only about one hundred intrinsic procedures. 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.
Operators F supports many of the standard operators used in Fortran. The operators supported by F are: • Arithmetic operators: +, -, *, /, ** • Relational operators: , , ==, /=, >, >= • Logical operators: .not., .and., .or., .eqv., .neqv. • character concatenation: // The assignment operator is denoted by the equal sign =. In addition, pointer assignment is denoted by =>. Comments are denoted by the ! symbol: variable = expression ! assignment pointer => target ! pointer assignment
Data types Similar to
Fortran, the type specification is made up of a type, a list of attributes for the declared variables, and the variable list. 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: real :: x, y ! declaring variables of type real x,y without an attribute list integer (kind = long), dimension (100) :: x ! declaring variable of type big integer array with the identifier x character (len = 100) :: student_name ! declaring a character type variable with length 100 F does not have intrinsic support for
object-oriented programming, but it does allow for
records: type, public :: City character (len = 100) :: name character (len = 50) :: state end type City Variable declarations are followed by an attribute list. The attributes allowed are parameter, public, private, allocatable, dimension, intent, optional,
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.
Statement and control flow 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. real :: x do i = 100 x = x+i print*,i cycle end do max : do if (x > y) then exit max end if x = y end do max stop if (x y) then x = y - x end if select case (maximum): case (0) x = 0 case (1) x = 1 case (5) x = 5 case default x = 10 end select F places a heavy emphasis on
modular programming. program main ! Insert code here end program main 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. 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. == References ==