Writing an 'online calculator' in fortran

[John Uebersax]

Here's what I'd like to do:

1. have a webpage form where user supplies a few parameter values
(e.g., to calculate, say, a chi-squared value)
2. users presses "submit" button
3. user-supplied values are written to a data or input file on my
server
4. a fortran program executes, reads the values, does calculations,
writes result to an output file
5. output values then populate fields on a results html page for the
user to view

There are of course many such calculators online -- though in
languages like java. I'm just looking for tips or advice how to do
the same thing with fortran. If I could find a simple example, I
could probably generalize it fairly easily.

Thanks in advance for any suggestions.

John Uebersax
http://www.rateragreement.com

[e p chandler]

A CGI program (common gateway interface) takes input from standard
input and/or environment variables and writes to standard output.

see http://www.nag.co.uk/nagware/Examples/cgi.f90

IIRC F2003 has standard facilities to deal with environment variables.

-- e

[e p chandler]

On Sep 16, 4:42 pm, John Uebersax <jsueber...@gmail.com> wrote:

There also are some Microsoft specific solutions to running server
side calculations in Fortran. Sorry I don't have example code or
pointers to code. Wrap up the Fortran code as an Active-X control and
call it from an ASP (Active Server Page).

-- e

[Jason Blevins]

The following tutorial is quite good. It works through three basic
tasks---parameter passing, uploading files, and handling variable length
text fields---and provides source code and sample forms for each. Each
example is a live demo as well.

http://www.nber.org/sys-admin/fortran-cgi/

--
Jason Blevins
Ph.D. Candidate, Department of Economics, Duke University
http://jblevins.org/

[John]

On Sep 16, 4:42 pm, John Uebersax <jsueber...@gmail.com> wrote:

See link below.
It's been used in web pages since the first month forms were
added to HTML (actually, a slightly different version that
included a steam table library -- the form asked for water/steam
properties and then calculated a table of all the properties for
that state the library could produce).

http://home.comcast.net/~urbanjost/CLONE/JUEXPR/juexpr.html

But unless you have a similar need (to interface with a large
library of existing Fortran) you can easily make a CGI script that
uses bc(1) or perl(1) or many many interpretive languages.

[John]

On Sep 16, 4:42 pm, John Uebersax <jsueber...@gmail.com> wrote:

PS:
Is JavaScript (ECMAscript) suitable? You can eliminate the CGI stuff
completely and have a single self-contained file someone can use off-
line,
among other benefits,

[baf]

A Fortran 90 cgi interface

http://flibs.sourceforge.net/cgi_protocol.html

[user1]

A Fortran version of strtok could be useful for breaking up the strings
that come from the cgi input. ( stuff looks like &val1=abcd&val2=1234 )

[Jason Blevins]

On Sep 17, 2009, at 9:46 AM, us...@example.net wrote:
> A Fortran version of strtok could be useful for breaking up the
> strings that come from the cgi input. ( stuff looks like
> &val1=abcd&val2=1234 )

Here is a strtok implementation, courtesy of John Urban:

http://fortranwiki.org/fortran/show/strtok

[Richard Maine]

Jason Blevins <jrbl...@sdf.lonestar.org> wrote:

> On Sep 17, 2009, at 9:46 AM, us...@example.net wrote:
> > A Fortran version of strtok could be useful for breaking up the
> > strings that come from the cgi input. ( stuff looks like
> > &val1=abcd&val2=1234 )
>
> Here is a strtok implementation, courtesy of John Urban:
>
> http://fortranwiki.org/fortran/show/strtok

Here's my equivalent, which I've used for nearly 2 decades, as you can
see from the date. This doesn't try to mimic the C strtok (and doesn't
have its limitations either). It is in a much more native Fortran style.

It is a little more complicated than some because it does some things
that I regularly find useful. For example, it can tell the caller what
trailing delimitter it found. This can be useful, for example, to
distinguish between

somefield, someotherfield

versus

somefield=somevalue, someotherfield

Also, I have a bit of special handling for blanks. All the usage
information is in the argument comments. Note that most of the arguments
are optional.

This is normally in a module. It does reference one other routine of
mine, but I presume the function of error_halt should be obvious.

subroutine find_field (string, field, position, delims, delim, found)

!-- Find a delimitted field in a string.
!-- 15 Nov 90, Richard Maine.

!-------------------- interface.
character*(*), intent(in) :: string !-- The string input.
character*(*), intent(out) :: field
!-- The returned field. Blank if no field found.
integer, optional, intent(inout) :: position
!-- On entry, the starting position for searching for the
field.
!-- Default is 1 if the argument is not present.
!-- On exit, the starting position of the next field or
!-- len(string)+1 if there is no following field.
character*(*), optional, intent(in) :: delims
!-- String containing the characters to be accepted as
delimitters.
!-- If this includes a blank character, then leading blanks are
!-- removed from the returned field and the end delimitter may
!-- optionally be preceeded by blanks. If this argument is
!-- not present, the default delimitter set is a blank.
character*(*), optional, intent(out) :: delim
!-- Returns the actual delimitter that terminated the field.
!-- Returns char(0) if the field was terminated by the end of
!-- the string or if no field was found.
!-- If blank is in delimitters and the field was terminated
!-- by one or more blanks, followed by a non-blank delimitter,
!-- the non-blank delimitter is returned.
logical, optional, intent(out) :: found
!-- True if a field was found.

!-------------------- local.
character :: delimitter*1
integer :: pos, field_start, field_end, i
logical :: trim_blanks

!-------------------- executable code.

field = ''
delimitter = char(0)
pos = 1
if (present(found)) found = .false.
if (present(position)) pos = position
if (pos > len(string)) goto 9000
if (pos < 1) call error_halt('Illegal position in find_field')

!-- Skip leading blanks if blank is a delimitter.
field_start = pos
trim_blanks = .true.
if (present(delims)) trim_blanks = index(delims,' ') /= 0
if (trim_blanks) then
i = verify(string(pos:),' ')
if (i == 0) then
pos = len(string) + 1
goto 9000
end if
field_start = pos + i - 1
end if
if (present(found)) found = .true.

!-- Find the end of the field.
if (present(delims)) then
i = scan(string(field_start:), delims)
else
i = scan(string(field_start:), ' ')
end if
if (i == 0) then
field_end = len(string)
delimitter = char(0)
pos = field_end + 1
else
field_end = field_start + i - 2
delimitter = string(field_end+1:field_end+1)
pos = field_end + 2
end if

!-- Return the field.
field = string(field_start:field_end)

!-- Skip trailing blanks if blank is a delimitter.
if (trim_blanks) then
i = verify(string(field_end+1:), ' ')
if (i == 0) then
pos = len(string) + 1
goto 9000
end if
pos = field_end + i

!-- If the first non-blank character is a delimitter,
!-- skip blanks after it.
i = 0
if (present(delims)) i = index(delims, string(pos:pos))
if (i /= 0) then
delimitter = string(pos:pos)
pos = pos + 1
i = verify(string(pos:), ' ')
if (i == 0) then
pos = len(string) + 1
else
pos = pos + i - 1
end if
end if
end if

!---------- Normal exit.
9000 continue
if (present(delim)) delim = delimitter
if (present(position)) position = pos
return
end subroutine find_field

--
Richard Maine | Good judgment comes from experience;
email: last name at domain . net | experience comes from bad judgment.
domain: summertriangle | -- Mark Twain