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INTEGER input question

NotThatItMatters
Beginner
121 Views

A development in my code has left me with the following "simple" INTEGER input question.  A single line in a text file has either one or two integer values, but a priori I do not know which.  How might I read this line and determine how many inputs?

My attempt was the following:

I2 = -1
READ(IOUNIT, *, ERR = 11) I1, I2
11 CONTINUE
IF (I2 == -1) THEN
! Do something appropriate to initialize I2
END IF

This fails because the error may have been triggered, but the READ statement is now gobbling more input.  What is the "best" way to do this?

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1 Solution
jimdempseyatthecove
Black Belt
121 Views

And for your follow-up question:

program read_x_y
    implicit none
    integer, parameter :: MaxInputLine=128
    character(len=MaxInputLine) :: InputLine
    integer, parameter :: N = 10
    integer :: Array(N)
    integer :: comma, i
    read(*,'(A)') InputLine
    Array = -1
    do i=1,N
        if(InputLine == ' ') exit
        read(InputLine,*) Array(i)
        comma = index(InputLine,',')
        if(comma <= 0) exit
        InputLine = InputLine(comma+1:)
    end do
    print *, Array
end program read_x_y

Jim Dempsey

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5 Replies
NotThatItMatters
Beginner
121 Views

Note: I am using Fortran 2003 as the standard for my code, so non-advancing input with appropriate settings is a viable option.

jimdempseyatthecove
Black Belt
121 Views
program read_x_y
    implicit none
    integer, parameter :: MaxInputLine=128
    character(len=MaxInputLine) :: InputLine
    integer :: i1, i2,comma
    read(*,'(A)') InputLine
    read(InputLine,*) i1
    i2=-1
    comma = index(InputLine,',')
    if(comma > 0) read(InputLine(comma+1:),*) i2
    print *, i1,i2
end program read_x_y

The above is one way to do this. You may want to improve the delimiter detection (space, tab, accept and evaluate an expression, etc...)

Jim Dempsey

jimdempseyatthecove
Black Belt
122 Views

And for your follow-up question:

program read_x_y
    implicit none
    integer, parameter :: MaxInputLine=128
    character(len=MaxInputLine) :: InputLine
    integer, parameter :: N = 10
    integer :: Array(N)
    integer :: comma, i
    read(*,'(A)') InputLine
    Array = -1
    do i=1,N
        if(InputLine == ' ') exit
        read(InputLine,*) Array(i)
        comma = index(InputLine,',')
        if(comma <= 0) exit
        InputLine = InputLine(comma+1:)
    end do
    print *, Array
end program read_x_y

Jim Dempsey

View solution in original post

NotThatItMatters
Beginner
121 Views

Thank you.  I had done some Googling and found a similar solution on StackOverflow.  It is working, and yours is more generic.  I will be implementing as such.

jimdempseyatthecove
Black Belt
121 Views

You might want to look on this forum a little more. Someone posted a really good input parser.

https://software.intel.com/pt-br/comment/1478224

There are more.

Jim Dempsey

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