Finding remaining months in a fiscal year - ruby

Question

I need to calculate the number of remaining months in a fiscal year from the given month, where a fiscal year starts from the fourth month of the year. I have an array illustrating this:
months = [4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2, 3]
Some expected inputs and outputs are:
4 => 11
10 => 5
2 => 1
However, when 3 is given (as well as when 2 is given), I want it to return 1 because the return value is used in a multiplication, and if it is 0, the output becomes 0.
I solved this by doing:
#month == 3 ?
annual_taxable_income += total_monthly_income_present_month :
annual_taxable_income += total_monthly_income_present_month + #basic_salary * fiscal_months_array[#month - 3, 12].size
I used ternary operator to check if there is 3, and if there is, then do not find the remaining months. The solution is working but I need a better way to do this.

Answer 1

def remaining_months(mon)
(3 - mon) % 12
end
(1..12).each { |mon| puts "#{mon} -> #{remaining_months(mon)}" }
1 -> 2
2 -> 1
3 -> 0
4 -> 11
5 -> 10
6 -> 9
7 -> 8
8 -> 7
9 -> 6
10 -> 5
11 -> 4
12 -> 3
You therefore would want [remaining_months(mon), 1].max. It's best not to put this part in the method remaining_months.
Note that the array months is determined by the first element, which is the first month of the fiscal year (4). It therefore should not be surprising that only the first element is needed in calculations.
Do you ever have problems like this where a modulus is involved and finding yourself trying different expressions until you finally find hit on one that works? Here's a way to do that for those in audience who are somewhat lazy by nature.
RESULT = [*(3..11), 0, 1, 2].reverse
a = [*(-12..0), *(1..12)]
a.product([1,-1], (a-[0]), a).
select do |c1,c2,c3,c4|
(1..12).all? { |mon| c1 + c2 * ((c3 * mon + c4) % 12) == RESULT[mon-1] }
end.
map do |c1,c2,c3,c4|
s1 = c1.zero? ? '' : c1.to_s
s2 = case c1.zero?
when true then c2==1 ? '' : '-'
else c2==1 ? ' + ' : ' - '
end
s3 = if c3 > 0
c3==1 ? '' : "#{c3} * "
else
c3==-1 ? '- ' : "- #{c3.abs} * "
end
s4 = case c4 <=> 0
when 0 then ''
when -1 then " - #{c4.abs}"
else " + #{c4}"
end
"#{s1}#{s2}((#{s3}mon#{s4}) % 12"
end
#=> ["((- mon - 9) % 12",
# "((- mon + 3) % 12",
# "(11 * mon - 9) % 12",
# "(11 * mon + 3) % 12",
# "11 - ((- 11 * mon - 4) % 12",
# "11 - ((- 11 * mon + 8) % 12",
# "11 - ((mon - 4) % 12",
# "11 - ((mon + 8) % 12"]
Take your pick!
Here we obtain the following intermediate result.
a.product([1,-1], (a-[0]), a).
select do |c1,c2,c3,c4|
(1..12).all? { |mon| c1 + c2 * ((c3 * mon + c4) % 12) == RESULT[mon-1] }
end
#=> [[0, 1, -1, -9], [0, 1, -1, 3], [0, 1, 11, -9], [0, 1, 11, 3],
# [11, -1, -11, -4], [11, -1, -11, 8], [11, -1, 1, -4], [11, -1, 1, 8]]

Answer 2

you could set the min value of the starting index value with max
fiscal_months = [4,5,6,7,8,9,10,11,12,1,2,3]
index = [#month-3, 1].max
annual_taxable_income += total_monthly_income_present_month + #basic_salary * fiscal_months[index, 12].size

Answer 3

It seems odd that you want a function that returns the same answer (1) for two different inputs (2,3). But, if that is the case you could do it like this. It is brute force but makes clear what you are trying to do:
def num_remaining_months_for (m)
fiscal_months = [4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2, 3]
remaining = [11, 10, 9, 8, 7, 6, 5, 4, 3 , 2, 1, 1]
index = fiscal_months.index(m)
remaining[index]
end
(1..12).each do |e|
puts "For month #{e} => #{num_remaining_months_for(e)} remaining"
end
The results are:
For month 1 => 2 remaining
For month 2 => 1 remaining
For month 3 => 1 remaining
For month 4 => 11 remaining
For month 5 => 10 remaining
For month 6 => 9 remaining
For month 7 => 8 remaining
For month 8 => 7 remaining
For month 9 => 6 remaining
For month 10 => 5 remaining
For month 11 => 4 remaining
For month 12 => 3 remaining

Answer 4

I would do it like that. I think it's clearer.
def number_of_remaining_months(month)
fiscal_months_array = [4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2, 3]
month = 2 if month == 3
fiscal_months_array.count - 1 - fiscal_months_array.index(month)
end
puts("Number of the month [1-12]:")
month = Integer(gets.chomp)
result = number_of_remaining_months(month)
annual_taxable_income = total_monthly_income_present_month +
#basic_salary * result
I hope it useful for you.