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Compact Fortran 95 Language Summary _7.1e+10

作者：木道寻08 | 2024-07-16 18:59:03

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发信人: Mars (FangQ), 信区: MathTools
标题: Compact Fortran 95 Language Summary [ZZ]
发信站: 达摩BigGreen BBS (Thu Dec 12 02:42:06 2002), 站内信件

Compact Fortran 95 Language Summary

This summary was extracted from various sources.
It is not intended to be 100% complete. Hopefully it will be
useful as a memory aid in writing Fortran programs.

Contents
Introduction to Fortran 95 Language
Meta language used in this compact summary
Structure of files that can be compiled
Executable Statements and Constructs
Declarations
Key words (other than I/O)
Key words related to I/O
Operators
Constants
Input/Output Statements
Formats
Intrinsic Functions
Other Links

Introduction to Fortran 95 Language ISO/IEC 1539:1995

Brought to you by ANSI committee X3J3 and ISO-IEC/JTC1/SC22/WG5 (Fortran)
This is neither complete nor precisely accurate, but hopefully, after
a small investment of time it is easy to read and very useful.

This is the free form version of Fortran, no statement numbers,
no C in column 1, start in column 1 (not column 7),
typically indent 2, 3, or 4 spaces per each structure.
The typical extension is .f90 .

Continue a statement on the next line by ending the previous line with
an ampersand & . Start the continuation with & for strings.

The rest of any line is a comment starting with an exclamation mark ! .

Put more than one statement per line by separating statements with a
semicolon ; . Null statements are OK, so lines can end with semicolons.

Separate words with space or any form of "white space" or punctuation.

Meta language used in this compact summary

means fill in something appropriate for xxx and do not type
the "<" or ">" .

... ellipsis means the usual, fill in something, one or more lines

[stuff] means supply nothing or at most one copy of "stuff"
[stuff1 [stuff2]] means if "stuff1" is included, supply nothing
or at most one copy of stuff2.

"old" means it is in the language, like almost every feature of past
Fortran standards, but should not be used to write new programs.

Structure of files that can be compiled

program                   usually file name is .f90
    use              bring in any needed modules
    implicit none                 good for error detection

           order is important, no more declarations
end program

block data old
common, dimension, equivalence now obsolete
end block data

module                    bring back in with   use
    implicit none                 good for error detection
                    can have private and public and interface
end module

subroutine                use: call    to execute
    implicit none                 good for error detection


end subroutine

subroutine (par1, par2, ...)
                                  use: call (arg1, arg2,... ) to execute
    implicit none                 optional, good for error detection
                    par1, par2, ... are defined in declarations
                                  and can be specified in, inout, pointer, etc.

    return                        optional, end causes automatic return
    entry (par...)         old, optional other entries
end subroutine

function (par1, par2, ...) result()
                                  use: (arg1, arg2, ... argn) as variable
    implicit none                 optional, good for error detection
                    rslt, par1, ... are defined in declarations

     =          required somewhere in execution
    [return]                      optional, end causes automatic return
end function

                                  old
   function(...)      use: (arg1, arg2, ... argn) as variable


     =          required somewhere in execution
    [return]                      optional, end causes automatic return
end function

Executable Statements and Constructs

will mean exactly one statement in this section

a construct is multiple lines

: any statement can have a label (a name)

= assignment statement

=> the pointer is now an alias for the variable
=> pointer1 now points same place as pointer2

stop                       can be in any executable statement group,
stop              terminates execution of the program,
stop               can have optional integer or string

return exit from subroutine or function

do =, [,] optional: : do ...

     exit                                   /_optional   or exit
     if () exit         /
                                            exit the loop
     cycle                                  /_optional   or cycle
     if () cycle        /
                                            continue with next loop iteration
end do                                    optional:    end do

do while ()
... optional exit and cycle allowed
end do

do
... exit required to end the loop
optional cycle can be used
end do

if ( ) execute the statement if the
boolean expression is true

if ( ) then
    ...                                    execute if expression1 is true
else if ( ) then
    ...                                    execute if expression2 is true
else if ( ) then
    ...                                    execute if expression3 is true
else
    ...                                    execute if none above are true
end if

select case ()            optional : select case ...
     case ()
                            execute if expression == value
     case (:)
                            execute if value1 <= expression <= value2
     ...
     case default
                            execute if no values above match
end select                            optional end select

real, dimension(10,12) :: A, R     a sample declaration for use with "where"
    ...
where (A /= 0.0)                   conditional assignment, only assignment allowed
     R = 1.0/A
elsewhere
     R = 1.0                         elements of R set to 1.0 where A == 0.0
end where     go to           old

go to (), old

for I/O statements, see: section 10.0 Input/Output Statements

many old forms of statements are not listed

Declarations

There are five (5) basic types: integer, real, complex, character and logical.
There may be any number of user derived types. A modern (not old) declaration
starts with a type, has attributes, then ::, then variable(s) names

integer i, pivot, query old

integer, intent (inout) :: arg1

integer (selected_int_kind (5)) :: i1, i2

integer, parameter :: m = 7

integer, dimension(0:4, -5:5, 10:100) :: A3D

double precision x old

real (selected_real_kind(15,300) :: x

complex :: z

logical, parameter :: what_if = .true.

character, parameter :: me = "Jon Squire"

type a new user type, derived type
declarations
end type

type () :: stuff declaring stuff to be of derived type

real, dimension(:,:), allocatable, target :: A

real, dimension(:,:), pointer :: P

Attributes may be:

    allocatable no memory used here, allocate later
    dimension    vector or multi dimensional array
    external     will be defined outside this compilation
    intent       argument may be in, inout or out
    intrinsic    declaring function to be an intrinsic
    optional     argument is optional
    parameter    declaring a constant, can not be changed later
    pointer      declaring a pointer
    private      in a module, a private declaration
    public       in a module, a public declaration
    save         keep value from one call to the next, static
    target       can be pointed to by a pointer
    Note:        not all combinations of attributes are legal

Key words (other than I/O)

note: "statement" means key word that starts a statement, one line
                    unless there is a continuation "&"
        "construct" means multiple lines, usually ending with "end ..."
        "attribute" means it is used in a statement to further define
        "old"       means it should not be used in new code

allocatable          attribute, no space allocated here, later allocate
allocate             statement, allocate memory space now for variable
assign               statement, old, assigned go to
assignment           attribute, means subroutine is assignment (=)
block data           construct, old, compilation unit, replaced by module
call                 statement, call a subroutine
case                 statement, used in select case structure
character            statement, basic type, intrinsic data type
common               statement, old, allowed overlaying of storage
complex              statement, basic type, intrinsic data type
contains             statement, internal subroutines and functions follow
continue             statement, old, a place to put a statement number
cycle                statement, continue the next iteration of a do loop
data                 statement, old, initialized variables and arrays
deallocate           statement, free up storage used by specified variable
default              statement, in a select case structure, all others
do                   construct, start a do loop
double precision     statement, old, replaced by selected_real_kind(15,300)
else                 construct, part of if   else if   else   end if
else if              construct, part of if   else if   else   end if
elsewhere            construct, part of where elsewhere end where
end block data       construct, old, ends block data
end do               construct, ends do
end function         construct, ends function
end if               construct, ends if
end interface        construct, ends interface
end module           construct, ends module
end program          construct, ends program
end select           construct, ends select case
end subroutine       construct, ends subroutine
end type             construct, ends type
end where            construct, ends where
entry                statement, old, another entry point in a procedure
equivalence          statement, old, overlaid storage
exit                 statement, continue execution outside of a do loop
external             attribute, old statement, means defines else where
function             construct, starts the definition of a function
go to                statement, old, requires fixed form statement number
if                   statement and construct, if(...) statement
implicit             statement, "none" is preferred to help find errors
in                   a keyword for intent, the argument is read only
inout                a keyword for intent, the argument is read/write
integer              statement, basic type, intrinsic data type
intent               attribute, intent(in) or intent(out) or intent(inout)
interface            construct, begins an interface definition
intrinsic            statement, says that following names are intrinsic
kind                 attribute, sets the kind of the following variables
len                  attribute, sets the length of a character string
logical              statement, basic type, intrinsic data type
module               construct, beginning of a module definition
namelist             statement, defines a namelist of input/output
nullify              statement, nullify(some_pointer) now points nowhere
only                 attribute, restrict what comes from a module
operator             attribute, indicates function is an operator, like +
optional             attribute, a parameter or argument is optional
out                  a keyword for intent, the argument will be written
parameter            attribute, old statement, makes variable real only
pause                old, replaced by stop
pointer              attribute, defined the variable as a pointer alias
private              statement and attribute, in a module, visible inside
program              construct, start of a main program
public               statement and attribute, in a module, visible outside
real                 statement, basic type, intrinsic data type
recursive            attribute, allows functions and derived type recursion
result               attribute, allows naming of function result result(Y)
return               statement, returns from, exits, subroutine or function
save                 attribute, old statement, keep value between calls
select case          construct, start of a case construct
stop                 statement, terminate execution of the main procedure
subroutine           construct, start of a subroutine definition
target               attribute, allows a variable to take a pointer alias
then                 part of if construct
type                 construct, start of user defined type
type ( )             statement, declaration of a variable for a users type
use                  statement, brings in a module
where                construct, conditional assignment
while                construct, a while form of a do loop

Key words related to I/O

backspace            statement, back up one record
close                statement, close a file
endfile              statement, mark the end of a file
format               statement, old, defines a format
inquire              statement, get the status of a unit
open                 statement, open or create a file
print                statement, performs output to screen
read                 statement, performs input
rewind               statement, move read or write position to beginning
write                statement, performs output

Operators

**    exponentiation
*     multiplication
/     division
+     addition
-     subtraction
//    concatenation
==    .eq. equality
/=    .ne. not equal
<     .lt. less than
>     .gt. greater than
<=    .le. less than or equal
>=    .ge. greater than or equal
.not.       complement, negation
.and.       logical and
.or.        logical or
.eqv.       logical equivalence
.neqv.      logical not equivalence, exclusive or

.eq. ==    equality, old
.ne. /=    not equal. old
.lt. <     less than, old
.gt. >     greater than, old
.le. <=    less than or equal, old
.ge. >=    greater than or equal, old

Other punctuation:

   / ... / used in data, common, namelist and other statements
   (/ ... /) array constructor, data is separated by commas
   6*1.0      in some contexts, 6 copies of 1.0
   (i:j:k)    in some contexts, a list i, i+k, i+2k, i+3k, ... i+nk<=j
   (:j)       j and all below
   (i:)       i and all above
   (:)        undefined or all in range

Constants

Logical constants:

.true. True
.false. False

Integer constants:

0 1 -1 123456789

Real constants:

0.0 1.0 -1.0 123.456 7.1E+10 -52.715E-30

Complex constants:

(0.0, 0.0) (-123.456E+30, 987.654E-29)

Character constants:

"ABC" "a" "123'abc$%#@!" " a quote "" "
'ABC' 'a' '123"abc$%#@!' ' a apostrophe '' '

Derived type values:

      type name
        character (len=30) :: last
        character (len=30) :: first
        character (len=30) :: middle
      end type name

      type address
        character (len=40) :: street
        character (len=40) :: more
        character (len=20) :: city
        character (len=2) :: state
        integer (selected_int_kind(5)) :: zip_code
        integer (selected_int_kind(4)) :: route_code
      end type address

      type person
        type (name) lfm
        type (address) snail_mail
      end type person

type (person) :: a_person = person( name("Squire","Jon","S."), &
address("106 Regency Circle", "", "Linthicum", "MD", 21090, 1936))

a_person%snail_mail%route_code == 1936

Input/Output Statements

    open ()
    open (unit=, file=, iostat=)
    open (unit=, ... many more, see below )

    close ()
    close (unit=, iostat=,
           err=, status="KEEP")

    read ()
    read (unit=, fmt=, iostat=,
          end=, err=)
    read (unit=, rec=)

    write ()
    write (unit=, fmt=, iostat=,
           err=)
    write (unit=, rec=)

print *,

rewind
rewind (, err=)

backspace
backspace (, iostat=)

endfile
endfile (, err=, iostat=)

    inquire ( , exists = )
    inquire ( file=<"name">, opened = , access = )
    inquire ( iolength = ) x, y, A   ! gives "recl" for "open"

    namelist //       defines a name list
    read(*,nml=)                     reads some/all variables in namelist
    write(*,nml=)                    writes all variables in namelist
    & = ... / data for namelist read

Input / Output specifiers

    access   one of "sequential" "direct" "undefined"
    action   one of "read" "write" "readwrite"
    advance one of "yes" "no"
    blank    one of "null" "zero"
    delim    one of "apostrophe" "quote" "none"
    end      =         old
    eor      =         old
    err      =         old
    exist    =
    file     =       <"file name">
    fmt      =       <"(format)"> or format
    form     one of "formatted" "unformatted" "undefined"
    iolength =
    iostat   =        0==good, negative==eof, positive==bad
    name     =
    named    =
    nml      =
    nextrec =           one greater than written
    number   =
    opened   =
    pad      one of "yes" "no"
    position one of "asis" "rewind" "append"
    rec      =
    recl     =
    size     =         number of characters read before eor
    status   one of "old" "new" "unknown" "replace" "scratch" "keep"
    unit     =

Individual questions
    direct      =      "yes" "no" "unknown"
    formatted   =      "yes" "no" "unknown"
    read        =      "yes" "no" "unknown"
    readwrite   =      "yes" "no" "unknown"
    sequential =      "yes" "no" "unknown"
    unformatted =      "yes" "no" "unknown"
    write       =      "yes" "no" "unknown"

Formats

    format                    an explicit format can replace * in any
                              I/O statement. Include the format in
                              apostrophes or quotes and keep the parenthesis.

    examples:
         print "(3I5,/(2X,3F7.2/))",
         write(6, '(a,E15.6E3/a,G15.2)' )

    A format includes the opening and closing parenthesis.
    A format consists of format items and format control items separated by comma.
    A format may contain grouping parenthesis with an optional repeat count.

Format Items, data edit descriptors:

    key: w is the total width of the field   (filled with *** if overflow)
          m is the least number of digits in the (sub)field (optional)
          d is the number of decimal digits in the field
          e is the number of decimal digits in the exponent subfield
          c is the repeat count for the format item
          n is number of columns

    cAw     data of type character (w is optional)
    cBw.m   data of type integer with binary base
    cDw.d   data of type real -- same as E, old double precision
    cEw.d   or Ew.dEe data of type real
    cENw.d or ENw.dEe data of type real -- exponent a multiple of 3
    cESw.d or ESw.dEe data of type real -- first digit non zero
    cFw.d   data of type real -- no exponent printed
    cGw.d   or Gw.dEe data of type real -- auto format to F or E
    nH      n characters follow the H, no list item
    cIw.m   data of type integer
    cLw     data of type logical -- .true. or .false.
    cOw.m   data of type integer with octal base
    cZw.m   data of type integer with hexadecimal base
    "" literal characters to output, no list item
    '' literal characters to output, no list item

Format Control Items, control edit descriptors:

    BN      ignore nonleading blanks in numeric fields
    BZ      treat nonleading blanks in numeric fields as zeros
    nP      apply scale factor to real format items   old
    S       printing of optional plus signs is processor dependent
    SP      print optional plus signs
    SS      do not print optional plus signs
    Tn      tab to specified column
    TLn     tab left n columns
    TRn     tab right n columns
    nX      tab right n columns
    /       end of record (implied / at end of all format statements)
    :       stop format processing if no more list items    can be:
    a variable
    an array name
    an implied do   ((A(i,j),j=1,n) ,i=1,m)    parenthesis and commas as shown

note: when there are more items in the input list than format items, the
repeat rules for formats applies.

   can be:
    a constant
    a variable
    an expression
    an array name
    an implied do   ((A(i,j),j=1,n) ,i=1,m)    parenthesis and commas as shown

note: when there are more items in the output list than format items, the
repeat rules for formats applies.

Repeat Rules for Formats:

    Each format item is used with a list item. They are used in order.
    When there are more list items than format items, then the following
    rule applies: There is an implied end of record, /, at the closing
    parenthesis of the format, this is processed. Scan the format backwards
    to the first left parenthesis. Use the repeat count, if any, in front
    of this parenthesis, continue to process format items and list items.

Note: an infinite loop is possible
print "(3I5/(1X/))", I, J, K, L may never stop

Intrinsic Functions

Intrinsic Functions are presented in alphabetical order and then grouped
by topic. The function name appears first. The argument(s) and result
give an indication of the type(s) of argument(s) and results.
[,dim=] indicates an optional argument "dim".
"mask" must be logical and usually conformable.
"character" and "string" are used interchangeably.
A brief description or additional information may appear.

Intrinsic Functions (alphabetical):

    abs(integer_real_complex) result(integer_real_complex)
    achar(integer) result(character) integer to character
    acos(real) result(real) arccosine |real| <= 1.0   0<=result<=Pi
    adjustl(character) result(character) left adjust, blanks go to back
    adjustr(character) result(character) right adjust, blanks to front
    aimag(complex) result(real) imaginary part
    aint(real [,kind=]) result(real) truncate to integer toward zero
    all(mask [,dim]) result(logical) true if all elements of mask are true
    allocated(array) result(logical) true if array is allocated in memory
    anint(real [,kind=]) result(real) round to nearest integer
    any(mask [,dim=}) result(logical) true if any elements of mask are true
    asin(real) result(real) arcsine |real| <= 1.0   -Pi/2<=result<=Pi/2
    associated(pointer [,target=]) result(logical) true if pointing
    atan(real) result(real) arctangent -Pi/2<=result<=Pi/2
    atan2(y=real,x=real) result(real) arctangent -Pi<=result<=Pi
    bit_size(integer) result(integer) size in bits in model of argument
    btest(i=integer,pos=integer) result(logical) true if pos has a 1, pos=0..
    ceiling(real) result(real) truncate to integer toward infinity
    char(integer [,kind=]) result(character) integer to character [of kind]
    cmplx(x=real [,y=real] [kind=]) result(complex) x+iy
    conjg(complex) result(complex) reverse the sign of the imaginary part
    cos(real_complex) result(real_complex) cosine
    cosh(real) result(real) hyperbolic cosine
    count(mask [,dim=]) result(integer) count of true entries in mask
    cshift(array,shift [,dim=]) circular shift elements of array, + is right
    date_and_time([date=] [,time=] [,zone=] [,values=]) y,m,d,utc,h,m,s,milli
    dble(integer_real_complex) result(real_kind_double) convert to double
    digits(integer_real) result(integer) number of bits to represent model
    dim(x=integer_real,y=integer_real) result(integer_real) proper subtraction
    dot_product(vector_a,vector_b) result(integer_real_complex) inner product
    dprod(x=real,y=real) result(x_times_y_double) double precision product
    eoshift(array,shift [,boundary=] [,dim=]) end-off shift using boundary
    epsilon(real) result(real) smallest positive number added to 1.0 /= 1.0
    exp(real_complex) result(real_complex) e raised to a power
    exponent(real) result(integer) the model exponent of the argument
    floor(real) result(real) truncate to integer towards negative infinity
    fraction(real) result(real) the model fractional part of the argument
    huge(integer_real) result(integer_real) the largest model number
    iachar(character) result(integer) position of character in ASCII sequence
    iand(integer,integer) result(integer) bit by bit logical and
    ibclr(integer,pos) result(integer) argument with pos bit cleared to zero
    ibits(integer,pos,len) result(integer) extract len bits starting at pos
    ibset(integer,pos) result(integer) argument with pos bit set to one
    ichar(character) result(integer) pos in collating sequence of character
    ieor(integer,integer) result(integer) bit by bit logical exclusive or
    index(string,substring [,back=]) result(integer) pos of substring
    int(integer_real_complex) result(integer) convert to integer
    ior(integer,integer) result(integer) bit by bit logical or
    ishft(integer,shift) result(integer) shift bits in argument by shift
    ishftc(integer, shift) result(integer) shift circular bits in argument
    kind(any_intrinsic_type) result(integer) value of the kind
    lbound(array,dim) result(integer) smallest subscript of dim in array
    len(character) result(integer) number of characters that can be in argument
    len_trim(character) result(integer) length without trailing blanks
    lge(string_a,string_b) result(logical) string_a>=string_b
    lgt(string_a,string_b) result(logical) string_a>string_b
    lle(string_a,string_b) result(logical) string_a<=string_b
    llt(string_a,string_b) result(logical) string_a=string_b
    lgt(string_a,string_b) result(logical) string_a>string_b
    lle(string_a,string_b) result(logical) string_a<=string_b
    llt(string_a,string_b) result(logical) string_a