Error Handling Patterns

Validation Flag

Count Problems

Validation often records facts about the data instead of stopping at the first problem. A logical mask and count summarize which entries need review.

Program

Play the program to choose the limit and count readings above it.

validation_flag.f90 
program validation_flag_demo
    implicit none
    integer :: readings(3)
    integer :: limit
    logical :: too_high(3)
    integer :: issue_count
    character(len=8) :: label

    readings = [4, 8, 12]
    limit = 
    too_high = readings > limit
    issue_count = count(too_high)
    if (issue_count == 0) then
        label = 'clean'
    else
        label = 'review'
    end if
    print '(A, 1X, I0)', trim(label), issue_count
end program validation_flag_demo

program validation_flag_demo
    implicit none
    integer :: readings(3)
    integer :: limit
    logical :: too_high(3)
    integer :: issue_count
    character(len=8) :: label

    readings = [4, 8, 12]
    limit = 
    too_high = readings > limit
    issue_count = count(too_high)
    if (issue_count == 0) then
        label = 'clean'
    else
        label = 'review'
    end if
    print '(A, 1X, I0)', trim(label), issue_count
end program validation_flag_demo

program validation_flag_demo
    implicit none
    integer :: readings(3)
    integer :: limit
    logical :: too_high(3)
    integer :: issue_count
    character(len=8) :: label

    readings = [4, 8, 12]
    limit = 
    too_high = readings > limit
    issue_count = count(too_high)
    if (issue_count == 0) then
        label = 'clean'
    else
        label = 'review'
    end if
    print '(A, 1X, I0)', trim(label), issue_count
end program validation_flag_demo
logical mask `readings > limit` compares every array element.
count `count(too_high)` converts validation flags into a summary number.
review label The final branch names whether the data is clean or needs review.