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Understanding Functions in Programming

Learn how to efficiently use subprograms, functions, and intrinsic functions to simplify code and enhance functionality in programming. Includes examples and exercises.

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Understanding Functions in Programming

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  1. LAB-06IF + Functions I Putu Danu Raharja raharja @kfupm.edu.sa Information & Computer Science Department CCSE - King Fahd University of Petroleum & Minerals

  2. Rationale • If you work on a program to solve a bigger problem, your program will become larger (more lines of code). • A large program is harder to debug (so far we have written programs < 100 lines but we still make mistakes) • Some of the code may be used several times.

  3. Subprogram • A big problem can be solved by dividing it into smaller sub-problems and conquering the sub-problems • A large program can be divided into simpler sub-programs that can be implemented and tested independently • Sub-programs can be reused

  4. Terminologies • Main program • Sub-program • Call & return • Function • Subroutine

  5. Function • A function consists of: • Function header • Function body • Function header type FUNCTION fname (list of arguments) • Function body • Declaration statements • Executable statements • Must have at least one RETURN statement • Must be ended with an END statement

  6. Example: Area of a triangle REAL FUNCTION TRAREA (A, B) REAL A, B TRAREA = A * B / 2 RETURN END REAL X, Y, AREA READ*, X, Y AREA = TRAREA(X, Y) PRINT*, 'Area = ', AREA END

  7. Intrinsic Functions • Functions which are available from the FORTRAN language (p. 63)

  8. Statement Function • Expressed as: fname (list of arguments) = expression • Example: TRA (BASE, HEIGHT) = BASE * HEIGHT * 0.5

  9. Exercises • A year with 366 days is called a leap year. A year is a leap year if it is divisible by 4 (for example, 1980), except that it is not a leap year if it is divisible by 100 (for example, 1900); however, it is a leap year if it is divisible by 400 (for example, 2000). There were no exceptions before the introduction of the Gregorian calendar on October 15, 1582 (for example, 1500 was a leap year). Write a logical function to determine whether the given year is a leap year.

  10. Exercise • Write a function that takes month and year as arguments and returns the number of days of that month. • Write a function that takes two real numbers and tests whether they are the same up to two decimal places. • Write a function that takes two times (hour and minute) in military format (09:00, 17:30) and computes the number of hours between the two times. You have to consider the case that the first time is later than the second time.

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