Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Validating user input

Validating user input

Validating user input

Does anyone have a function similiar to Visual Basic's "IsNumeric" for Fortran?  I'm trying to validate input from a dialog box and find the READ statements IOSTAT and ERR kind of klunky.

RE: Validating user input

Here's a simple little routine that will help you validate real numbers.   It is written in Fortran 90/95.   You'll want k8 to be equal to 8 for most double precision variables on most PC computers.   Make it 4 for single precision on most PC computers.   This code is tested and used on software which I've written.   If you're using Fortran 77,  you'll need to do some  alterations.   The intent of the code below should be sufficient for you to figure out how to alter it appropriately.


        SUBROUTINE  Validate_Real_k8 ( StrNum, value, valid )
        ! Check to see that a character string represents a valid real number
        ! Valid real numbers have the following attributes:
        !   They are representable by the fortran compiler used with this code.
        !   ie. No error is flagged when attempting to use a READ statement on
        !   the data, <StrNum>.
        !   They do NOT begin or end with the any of the following letters:
        !     eEdDqQ
        !   They do not contain embedded blank characters.
        !   If <StrNum> is all blanks, that is still considered a valid number.
        ! Input:
        !   StrNum = Character string which is supposed to represent a valid
        !       real number. StrNum is not altered by this routine.
        !       StrNum may be up to 50 character digits (including decimal, etc)
        ! Output:
        !   valid = .true.  if num is a valid real number or is all spaces.
        !         = .false. otherwise.
        !   value = Numeric value from StrNum if valid is .true.
        !         = 0.0 if the value from StrNum if valid = .false.
        !         = A variable with a Kind Type of "K8"
        ! Uses:
        !   KindTypes = module holding valid kind type parameters
        USE KindTypes
        Character(*),     intent(in)      :: StrNum
        Real(k8),            intent(inout) :: value
        Logical,              intent(out)   :: valid
        Character(Len(StrNum))        :: num
        Integer                              :: io
        Character(1)                      :: fd, ld

        num = ADJUSTL ( StrNum )
        Read ( num, '(F50.0)', iostat=io ) value
        IF ( io /= 0 ) THEN
            ! the entered value is not a valid 'real' number
            valid = .false.
            value = 0.0
        END IF

        io = Len_Trim ( num )
        fd = num(1:1)         ! first digit
        ld = num(io:io)       ! last  digit
        IF ( fd=='e' .OR. fd== 'E' .OR. ld=='e' .OR. ld== 'E' .OR. &
             fd=='d' .OR. fd== 'D' .OR. ld=='d' .OR. ld== 'D' .OR. &
             fd=='q' .OR. fd== 'Q' .OR. ld=='q' .OR. ld== 'Q' .OR. &
             INDEX(num(1:io),' ') /= 0                                 ) THEN
            ! Some compilers will accept a real number starting or ending
            ! with just a 'd' or an 'e'.  I don't consider this a valid entry
            ! LF95 ver 5.5 does this.  Also,  LF95,5.0 allows q or Q to be
            ! used to denote exponentiation just as E and D are used.
            valid = .false.
            value = 0.0
            valid = .true.
        END IF
        END SUBROUTINE  Validate_Real_k8

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close