Tagged CTFE
One of the most distinctive features of Common Lisp and Lisp in general, are its code-generation and code-manipulation capabilities.
Probably the best example is the LOOP macro - a Swiss Army knife of iteration that can do pretty much anything. The following snippet iterates a list of random numbers collecting some statistics of its contents and does that while being very concise and readable:
(let ((random (loop with max = 500
for i from 0 to max
collect (random max))))
(loop for i in random
counting (evenp i) into evens
counting (oddp i) into odds
summing i into total
maximizing i into max
minimizing i into min
finally (format t "Stats: ~A"
(list min max total evens odds))))
Stats: (0 499 120808 261 240)
Romans, rubies and the D
Posted on by Idorobots
There's an increasing interest with the D programming language amongst my readers so I figured I'll post a bunch of short posts about D and see what happens.
Anyway, here's a classic example showing Ruby's capabilities taken from Seven Languages in Seven Weeks:
class Roman
def self.method_missing name, *args
roman = name.to_s
roman.gsub!("IV", "IIII")
roman.gsub!("IX", "VIIII")
roman.gsub!("XL", "XXXX")
roman.gsub!("XC", "LXXXX")
(roman.count("I") +
roman.count("V") * 5 +
roman.count("X") * 10 +
roman.count("L") * 50 +
roman.count("C") * 100)
end
end
puts Roman.X
puts Roman.XC
puts Roman.XII