langref.org - ruby and clojure - Structure

Perform an action if a condition is true (IF .. THEN)

Given a variable name, if the value is "Bob", display the string "Hello, Bob!". Perform no action if the name is not equal.

ruby

if (name=='Bob')
puts "Hello, Bob!"
end

puts "Hello, Bob!" if name=='Bob'

clojure

(def person "Bob")
(if (= person "Bob")
(println "Hello, Bob!"))

Perform different actions depending on a boolean condition (IF .. THEN .. ELSE)

Given a variable age, if the value is greater than 42 display "You are old", otherwise display "You are young"

ruby

if (age > 42)
puts "You are old"
else
puts "You are young"
end

puts (age>42) ? "You are old" : "You are young"

puts "You are #{age > 42 ? "old" : "young"}"

clojure

(def age 41)
(if (> age 42) "You are old" "You are young")

Perform different actions depending on several boolean conditions (IF .. THEN .. ELSIF .. ELSE)

ruby

if age > 84
puts "You are really ancient"
elsif age > 30
puts "You are middle-aged"
else
puts "You are young"
end

case
when age > 84 then puts "You are really ancient"
when age > 30 then puts "You are middle-aged"
else puts "You are young"
end

clojure

(println
(condp <= age
84 "You are really ancient"
30 "You are middle aged"
"You are young"))

Replacing a conditional with many branches with a switch/case statement

Many languages support more compact forms of branching than just if ... then ... else such as switch or case or match. Use such a form to add an appropriate placing suffix to the numbers 1..40, e.g. 1st, 2nd, 3rd, 4th, ..., 11th, 12th, ... 39th, 40th

ruby

def suffixed(number)
last_digit = number.to_s[-1..-1].to_i
suffix = case last_digit
when 1 then 'st'
when 2 then 'nd'
when 3 then 'rd'
else 'th'
end
suffix = 'th' if (11..13).include?(number)
"#{number}#{suffix}"
end

(1..40).each {|n| puts suffixed(n) }

clojure

(def n 112)

(println (str n
(let [rem (mod n 100)]
(if (and (>= rem 11) (<= rem 13))
"th"
(condp = (mod n 10)
1 "st"
2 "nd"
3 "rd"
"th")))))