Computing the cross product of two vectors in Fortran 90

by

The best practice is to place your procedures (subroutines and functions) in a module and then “use” that module from your main program or other procedures. You don’t need to “use” the module from other procedures of the same module. This will make the interface of the procedure explicit so that the calling program or procedure “knows” the characteristics of the arguments … it allows the compiler to check for consistency between the arguments on both sides … caller and callee .. this eliminates a lot of bugs.

Outside of the language standard, but in practice necessary: if you use one file, place the module before the main program that uses it. Otherwise the compiler will be unaware of it. so:

module my_subs

implicit none

contains

FUNCTION cross(a, b)
  INTEGER, DIMENSION(3) :: cross
  INTEGER, DIMENSION(3), INTENT(IN) :: a, b

  cross(1) = a(2) * b(3) - a(3) * b(2)
  cross(2) = a(3) * b(1) - a(1) * b(3)
  cross(3) = a(1) * b(2) - a(2) * b(1)
END FUNCTION cross

end module my_subs


PROGRAM crosstest
  use my_subs
  IMPLICIT NONE

  INTEGER, DIMENSION(3) :: m, n
  INTEGER, DIMENSION(3) :: r

  m= [ 1, 2, 3 ]
  n= [ 4, 5, 6 ]
  r=cross(m,n)
  write (*, *) r

END PROGRAM crosstest

More Related Contents:

  1. Correct use of modules, subroutines and functions in Fortran
  2. Passing external function of multiple variables as a function of one variable in Fortran
  3. Procedure with assumed-shape dummy argument must have an explicit interface [duplicate]
  4. How to alias a function name in Fortran
  5. Does Fortran preserve the value of internal variables through function and subroutine calls?
  6. Proper use of modules in Fortran
  7. Difference between method and function in Scala
  8. What is the difference between a ‘closure’ and a ‘lambda’?
  9. Value receiver vs. pointer receiver
  10. How to explain callbacks in plain english? How are they different from calling one function from another function?
  11. Define table and column names as arguments in a plpgsql function?
  12. Committing transactions while executing a postgreql Function
  13. Non exhaustive pattern in function in GHCi
  14. How is the square root function implemented? [closed]
  15. Static vs class functions/variables in Swift classes?
  16. Whats the difference of functions and methods in Go?
  17. R: 2 functions with the same name in 2 different packages
  18. Define a recursive function within a function in Go
  19. When is a function too long? [closed]
  20. Two ways of defining functions in Scala. What is the difference?
  21. Kotlin: How can I create a “static” inheritable function?
  22. use onedit() trigger on a specific sheet within google scripts for google sheets
  23. How can I generate a list of function dependencies in MATLAB?
  24. MsgBox “” vs MsgBox() in VBScript
  25. Why can’t ‘kotlin.Result’ be used as a return type?
  26. How to evaluate functions in GDB?
  27. MATLAB error: Undefined function or method X for input arguments of type ‘double’ [duplicate]
  28. Matlab ode45. How to change a parameter inside it while calling it?
  29. How do you strip the unit from any number in SASS?
  30. In R, what exactly is the problem with having variables with the same name as base R functions?

Leave a Comment