Table-Driven Calculations

Threshold Bracket Table

Last Matching Row

A bracket table can scan thresholds and keep the last matching row.

Program

Play the program to change an amount and see which bracket is selected.

threshold_bracket_table.f90 
program threshold_bracket_table_demo
    implicit none
    integer :: minimums(3)
    integer :: factors(3)
    integer :: amount
    integer :: i
    integer :: selected_factor
    integer :: adjusted

    minimums = [0, 10, 20]
    factors = [1, 2, 3]
    amount = 
    selected_factor = factors(1)
    do i = 1, 3
        if (amount >= minimums(i)) selected_factor = factors(i)
    end do
    adjusted = amount * selected_factor
    print '(I0, 1X, I0)', selected_factor, adjusted
end program threshold_bracket_table_demo

program threshold_bracket_table_demo
    implicit none
    integer :: minimums(3)
    integer :: factors(3)
    integer :: amount
    integer :: i
    integer :: selected_factor
    integer :: adjusted

    minimums = [0, 10, 20]
    factors = [1, 2, 3]
    amount = 
    selected_factor = factors(1)
    do i = 1, 3
        if (amount >= minimums(i)) selected_factor = factors(i)
    end do
    adjusted = amount * selected_factor
    print '(I0, 1X, I0)', selected_factor, adjusted
end program threshold_bracket_table_demo

program threshold_bracket_table_demo
    implicit none
    integer :: minimums(3)
    integer :: factors(3)
    integer :: amount
    integer :: i
    integer :: selected_factor
    integer :: adjusted

    minimums = [0, 10, 20]
    factors = [1, 2, 3]
    amount = 
    selected_factor = factors(1)
    do i = 1, 3
        if (amount >= minimums(i)) selected_factor = factors(i)
    end do
    adjusted = amount * selected_factor
    print '(I0, 1X, I0)', selected_factor, adjusted
end program threshold_bracket_table_demo
threshold table Threshold rows describe which factor applies for each amount range.
last match Scanning in order keeps the factor from the last satisfied threshold.
table-driven branch Changing the table data can change the decision without changing the loop shape.