How to resolve the algorithm Nested function step by step in the Fortran programming language

Published on 12 May 2024 09:40 PM
#Fortran

How to resolve the algorithm Nested function step by step in the Fortran programming language

Table of Contents

Problem Statement

In many languages, functions can be nested, resulting in outer functions and inner functions. The inner function can access variables from the outer function. In most languages, the inner function can also modify variables in the outer function.

Write a program consisting of two nested functions that prints the following text. The outer function (called MakeList or equivalent) is responsible for creating the list as a whole and is given the separator ". " as argument. It also defines a counter variable to keep track of the item number. This demonstrates how the inner function can influence the variables in the outer function. The inner function (called MakeItem or equivalent) is responsible for creating a list item. It accesses the separator from the outer function and modifies the counter.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Nested function step by step in the Fortran programming language

Source code in the fortran programming language

      FUNCTION F(X)
       REAL X
       DIST(U,V,W) = X*SQRT(U**2 + V**2 + W**2)    !The contained function.
        T = EXP(X)
        F = T + DIST(T,SIN(X),ATAN(X) + 7)         !Invoked...
      END


      SUBROUTINE POOBAH(TEXT,L,SEP)	!I've got a little list!
       CHARACTER*(*) TEXT	!The supplied scratchpad.
       INTEGER L		!Its length.
       CHARACTER*(*) SEP	!The separator to be used.
       INTEGER N		!A counter.
        L = 0			!No text is in place.
        N = 0			!No items added.
        CALL ADDITEM("first")	!Here we go.
        CALL ADDITEM("second")
        CALL ADDITEM("third")
       CONTAINS		!Madly, defined after usage.
        SUBROUTINE ADDITEM(X)	!A contained routine.
         CHARACTER*(*) X	!The text of the item.
          N = N + 1			!Count another item in.
          TEXT(L + 1:L + 1) = CHAR(ICHAR("0") + N)	!Place the single-digit number.
          L = L + 1			!Rather than mess with unknown-length numbers.
          LX = LEN(SEP)			!Now for the separator.
          TEXT(L + 1:L + LX) = SEP	!Placed.
          L = L + LX			!Advance the finger.
          LX = LEN(X)			!Trailing spaces will be included.
          TEXT(L + 1:L + LX) = X	!Placed.
          L = L + LX			!Advance the finger.
          L = L + 1			!Finally,
          TEXT(L:L) = CHAR(10)		!Append an ASCII line feed. Starts a new line.
        END SUBROUTINE ADDITEM	!That was bitty.
      END SUBROUTINE POOBAH	!But only had to be written once.

      PROGRAM POKE
      CHARACTER*666 TEXT	!Surely sufficient.
      INTEGER L
      CALL POOBAH(TEXT,L,". ")
      WRITE (6,"(A)") TEXT(1:L)
      END


      SUBROUTINE POOBAH(TEXT,N,SEP)	!I've got a little list!
       CHARACTER*(*) TEXT(*)	!The supplied scratchpad.
       INTEGER N		!Entry count.
       CHARACTER*(*) SEP	!The separator to be used.
        N = 0			!No items added.
        CALL ADDITEM("first")	!Here we go.
        CALL ADDITEM("second")
        CALL ADDITEM("third")
       CONTAINS		!Madly, defined after usage.
        SUBROUTINE ADDITEM(X)	!A contained routine.
         CHARACTER*(*) X	!The text of the item to add.
          N = N + 1			!Count another item in.
          WRITE (TEXT(N),1) N,SEP,X	!Place the N'th text, suitably decorated..
    1     FORMAT (I1,2A)		!Allowing only a single digit.
        END SUBROUTINE ADDITEM	!That was simple.
      END SUBROUTINE POOBAH	!Still worth a subroutine.

      PROGRAM POKE
      CHARACTER*28 TEXT(9)	!Surely sufficient.
      INTEGER N
      CALL POOBAH(TEXT,N,". ")
      WRITE (6,"(A)") (TEXT(I)(1:LEN_TRIM(TEXT(I))), I = 1,N)
      END

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