Fortran 77

Confronto tra Fortran 77 e Matlab

Un confronto tra le caratteristiche principali del Fortran 77 e del software Matlab

Se si conosce un linguaggio di programmazione, è facile apprendere le basi di un qualsiasi altro linguaggio.la logica sulla quale sono stati realizzati è pressoccchè la stessa, naturalmente la sintassi è completamente differente.Di seguito abbiamo confrontato le caratteristiche principali dei due linguaggi Fortran 77 e Matlab.

MATLAB                   FORTRAN F77


Ambiente di programmazione


Path per funzioni & M-files:          Path per librerie

  set in DOS                             set in DOS

    set matlabpath=???                     set lib=???

  set in matlabrc.m for Windows

    matlabpath['???']

  set in matlab program

    path('c:\', path)

  other path commands

    path, pwd, cd



Preferred usage:

  2 windows (editor, command)          2 windows (editor, DOS for 
                                       compile-link-run)



Inteprete                              Compilatore



Velocità: 
Lento come una tartaruga               Veloce come un coniglio

  
Sintassi


% comments                             c comments

Columns: all                           Columns 7-72 for statements

Case Sensitive                         Case insensitive

Ignore blank spaces and lines.         Ignore blank spaces and lines.

Everything is a matrix.                Scalar (default=real/integer)

  the whole vector/matrix: x, A          x, A

  an element: x(1), A(1,1)               x(1), A(1,1)

  dimension: <=2 (in v4.0)             dimension may be > 2  (e.g., A(1,2,3))

Array size is dynamically adjusted.    Array size must be declared/fixed

                                       (F90 allows adjustable array size.)

No type declaration                    REAL, INTEGER, CHARACTER, LOGICAL ...

(more efficient with preallocation)

  e.g., A = zeros(2,3)                   e.g., REAL A(2,3)

Matrix stored in column-wise order     Matrix stored in column-wise order

  A = [ 1 2 3; 4 5 6];                     data A/1, 4, 2, 5, 3, 6/

  fprintf('%i\n',A) ... column-wise order  print *, A ... column-wise order

Complex number: x = 1 + 2*i            COMPLEX x;  x = CMPLX(1., 2.)

Logical variable (none)                LOGICAL declaration

  1 for true; 0 for false                .true. .false.

Algebraic operators: + - * / ^         + - * / **

Element-wise operator: "."

Transpose:           '                 (user provided)

Logical operators:

  < <= > >= == ~=                      .lt. .le. .gt. .ge. .eq. .ne.

  & | ~                                .and. .or. .not.



MATLAB and FORTRAN share the same algebraic function names

  sin, cos, tan, asin, acos, atan, exp, abs, etc.

  exception:

    sqrt: negative augument is ok          sqrt: positive argument only

    (-27)^0.3333 gives 1.5+2.6i (not -3)   domain error

    log                                    alog   (i.e., natural logarithm)

    log10                                  alog10 (i.e., common logarithm)

    rem                                    mod



Other conversion functions

  int8, int16, int32                       int

  num2str, int2str

  uint8('A')                               ichar('A')



Continuation:   ...                    column 6

Multiple statements separated by:

  "," or ";"                           none



Direttve di I/O



x                                      print *, 'x = ', x

x+y                                    print *, 'ans = ', x+y

y=x+1; (assignment)                    y=x+1

disp(' ')                              print *, ' '    or   write(*,*)

disp('text string')                    print *, 'text string'

disp(x)                                print *, x

disp(['x = ', num2str(x)])             print *, 'x = ', x

x=input('enter x  ')                   print *, 'enter x'  ;  read *, x

resp=input('Y/N  ', 's')               print *, 'Y/N:' ;  read '(a)', resp

(i.e., input a string; need to declare "CHARACTER resp" 
in FORTRAN)

sprintf('format string', x);           write(*,'(format string)') x

  where format: %e, %f, %g, %s

                %15.3e, %15.7f, %15.7g,  e15.3, f15.7, g15.7,

                %8s, %7i                 a8, i7

                \n (new line)               /

fprintf('filename', 'format', [x, y])  open (1, file='filename') ... one shot

                                       write(1,'(format)') x, y

load x.dat or load x.ext               read an ascii file into a variable x

save file variable_list /ascii         save the specified variables in a file



fid=fopen('filename', 'r' )            open(fid, 'filename', status='old')

fid=fopen('filename', 'w' )            open(fid, 'filename', status='new')

  where standard input  fid=0             standard input  fid=5

        standard output fid=1             standard output fid=6



x = fscanf(0, 'format', size)          read (5, '(format)') x

fprintf(1, 'format', x, y, z)          write(6, '(format)') x, y, z

fprintf('format', x, y, z)             write(*, '(format)') x, y, z



fclose(1)                              close(1)



Grafici



plot                                   No standard graphing functions,

axis([xmin,xmax,ymin,ymax])            but most compilers provide a system-

title('title')                         dependent set of graphing functions.

xlabel('xlabel'), ylabel('ylabel')

text



Cicli



DO-Loop

  for i=1:n                            do i=1, n

    :                                    :

    (return/keyboard/pause/break)        (return/stop/goto/exit)

  end                                  enddo



  One line format:

  for i=1:n statement; statement; end



  for i=n:-1:1    ... decrement i      do i=n, 1, -1    ... decrement i

    :                                    :

    (return/keyboard/pause/break)        (return/stop/goto/exit)

  end                                  enddo



WHILE

  while condition                      do while (condition)

    :                                    :

    (return/keyboard/pause/break)        (return/stop/goto/exit)

  end                                  enddo



Strutture condizionali



IF

  if condition                         if (condition) then

    :                                    :

  elseif condition                     elseif (condition) then

    :                                    :

  else                                 else

    :                                    :

  end                                  endif



SELECT-CASE (MATLAB v5)

  switch expression                    select case (resp)

    case 0                               case ('y')

      statements1                          statements1

    case 1                               case ('a', 'b')

      statements2                          statements2

    case 2                               case ('c':'f', 'h':'j')

      statements3                          statements3

    otherwise                            case default

      statements4                          statements4

  end                                  end select



Salti

  none                                 goto label



Programmi e strutture principali e
subroutine



Script file

  % comments                           program main

    (1st blank line)                   c comments

  % further comments                   statements

  statements                             :

  error('text string')                 stop 'text string'

                                       end

  (may have several script files)      (can have only one main program)



Subroutine senzat variabili di ritorno

  function dummy_name(arguments)       subroutine name(arguments)

  % comments                           c comments

       (1st blank line)                    statements

  % further comments                         :

  statements                                 :

  (return)                                 (return)

  Calling convention:

    foo(arguments)

    Similar to a plain script          end



Funzioni Scalari 

  function y = dummy_name(arguments)   function y(arguments)

  % comments                           c comments

       (1st blank line)                    statements

  % further comments                         :

  statements                                 :

  y = ....                                 y = ...

  (Assignment is made to y.)               (Assignment is made to 
                                            function name)

  (y may be a matrix.)                     end



Funzioni con Multiple-output 

  function [y1, y2] = dummy_name(arguments)

  % comments

       (1st blank line)

  % further comments

  statements                           Return multiple choices 
                                       with FUNCTION F(..., choice)

  y1 = ....                            Return multiple variables 
                                       with SUBROUTINE

  y2 = ....

  (All return variables must be on LHS

  grouped in "[?,?]" .)

  The LHS is NOT a matrix; thus, the

  dimensions of y1 and y2 need not match.

  Calling convension (/w or /wo comma):

    [y1 y2]=foo(...)

    [y1,y2]=foo(...)



Modo alternativo di passare le variabili

  global x y z                         common x, y, z

                                       common /cblock/ x, y, z


(Caution: v3 forced globalization within the entire MATLAB! 
Choose names wisely.)

v4 extends globalization within only the functions in which
global is declared.)
Function arguments should not appear in "global" or "common" 
list.



Funzioni senza argomenti

  y = dummy_name ()                    function name()

  Calling convension: y=foo            Calling convension: y=name()

  (Note: no parentheses!)





Each function stored in a separate     Multiple subroutines in one file.

  M-file.                               (No restriction.)

A copy of the argument is passed       Address of the argument is passed.

  to a function.  Passing by value.      Passing by address/pointer.

  (Nothing is returned via arguments!)  (Subroutine/function can return variables

                                         in the argument list)

    

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