Exercises from Chapter 9
Improved ask Method
How you could do it:
def ask question |
while true |
puts question |
reply = gets.chomp.downcase |
if reply == 'yes' |
return true |
end |
if reply == 'no' |
return false |
end |
|
|
puts 'Please answer "yes" or "no".' |
end |
end |
likes_it = ask 'Do you like eating tacos?' |
puts likes_it |
| <= | Do you like eating tacos? |
| => | yes |
| <= | true |
How I would do it:
def ask question |
while true |
puts question |
reply = gets.chomp.downcase |
return true if reply == 'yes' |
return false if reply == 'no' |
puts 'Please answer "yes" or "no".' |
end |
end |
puts(ask('Do you like eating tacos?')) |
| <= | Do you like eating tacos? |
| => | yes |
| <= | true |
Old-School Roman Numerals
How you could do it:
def old_roman_numeral num |
roman = '' |
|
roman = roman + 'M' * (num / 1000) |
roman = roman + 'D' * (num % 1000 / 500) |
roman = roman + 'C' * (num % 500 / 100) |
roman = roman + 'L' * (num % 100 / 50) |
roman = roman + 'X' * (num % 50 / 10) |
roman = roman + 'V' * (num % 10 / 5) |
roman = roman + 'I' * (num % 5 / 1) |
roman |
end |
puts(old_roman_numeral(1999)) |
How I would do it:
def old_roman_numeral num |
raise 'Must use positive integer' if num <= 0 |
roman = '' |
|
roman << 'M' * (num / 1000) |
roman << 'D' * (num % 1000 / 500) |
roman << 'C' * (num % 500 / 100) |
roman << 'L' * (num % 100 / 50) |
roman << 'X' * (num % 50 / 10) |
roman << 'V' * (num % 10 / 5) |
roman << 'I' * (num % 5 / 1) |
|
roman |
end |
puts(old_roman_numeral(1999)) |
“Modern” Roman Numerals
How you could do it:
def roman_numeral num |
thous = (num / 1000) |
hunds = (num % 1000 / 100) |
tens = (num % 100 / 10) |
ones = (num % 10 ) |
|
roman = 'M' * thous |
|
if hunds == 9 |
roman = roman + 'CM' |
elsif hunds == 4 |
roman = roman + 'CD' |
else |
roman = roman + 'D' * (num % 1000 / 500) |
roman = roman + 'C' * (num % 500 / 100) |
end |
|
if tens == 9 |
roman = roman + 'XC' |
elsif tens == 4 |
roman = roman + 'XL' |
else |
roman = roman + 'L' * (num % 100 / 50) |
roman = roman + 'X' * (num % 50 / 10) |
end |
|
if ones == 9 |
roman = roman + 'IX' |
elsif ones == 4 |
roman = roman + 'IV' |
else |
roman = roman + 'V' * (num % 10 / 5) |
roman = roman + 'I' * (num % 5 / 1) |
end |
|
roman |
end |
|
puts(roman_numeral(1999)) |
How I would do it:
def roman_numeral num |
raise 'Must use positive integer' if num <= 0 |
|
digit_vals = [['I', 5, 1], |
['V', 10, 5], |
['X', 50, 10], |
['L', 100, 50], |
['C', 500, 100], |
['D', 1000, 500], |
['M', nil, 1000]] |
|
roman = '' |
remaining = nil |
|
|
build_rev = proc do |l,m,n| |
num_l = m ? (num % m / n) : (num / n) |
full = m && (num_l == (m/n - 1)) |
|
if full && (num_l>1 || remaining) |
|
remaining ||= l |
else |
if remaining |
roman << l + remaining |
remaining = nil |
end |
|
roman << l * num_l |
end |
end |
|
digit_vals.each {|l,m,n| build_rev[l,m,n]} |
|
roman.reverse |
end |
|
puts(roman_numeral(1999)) |
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