CODEWITHSUNDEEP
fortran
tumchaaditya
tumchaaditya

Reputation: 1297

Handle user input type mismatch in FORTRAN

I am building a basic program in Silverfrost FTN5 wherein I input an integer from user.
If user enters a float value, it throws an error and the program ends. Is there any way I can handle this invalid input and ask user to enter valid input?

Upvotes: 0

Views: 644

Answers (1)

M. S. B.
M. S. B.

Reputation: 29391

There are several methods. 1) Read the input into a string and parse the string. If the string contains a period, reject it and re-ask for input. If the string appears valid, do an "internal" read of the integer from the string: read (string, *) IntVal. 2) More robust since this gracefully detects all errors: use the IOSTAT= keyword in your read statement. If the value is non-zero, there was an error ... re-ask for input.

EDIT: Code example:

program TestRead

integer :: number, ReadStatus

write (*, '( "Input integer: " )', advance="no" )
ReadInt: do
   read (*, *, iostat=ReadStatus) number
   if ( ReadStatus == 0 ) then
      exit ReadInt
   else
      write (*, '( / "READ ERROR: please re-input:" )' )
   end if
end do ReadInt

write (*, '( / "Value read: ", I0 )' )  number

end program TestRead

Upvotes: 2

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