Crystal 0.13.0 released!

07 Mar 2016 por asterite

This release includes some compiler and standard library fixes, as well as a bunch of additions. Let’s see some of them.

Special handling of case with tuple literals

There’s now special language support for matching multiple values. For example, FizzBuzz can now be written like this, using an underscore (_) to match any value:

(1..100).each do |i|
  case {i % 3, i % 5}
  when {0, 0}
    puts "FizzBuzz"
  when {0, _}
    puts "Fizz"
  when {_, 0}
    puts "Buzz"
  else
    puts i
  end
end

With this new syntax you can also match types, and variables inside a when body are known by the compiler to have those types:

a = rand < 0.5 ? 1 : "hello"
b = rand < 0.5 ? 2 : "bye"

case {a, b}
when {Int32, Int32}
  puts "Both ints: #{a + 1}, #{b + 1}"
when {String, String}
  puts "Both strings: #{a.upcase}, #{b.upcase}"
else
  puts "Other: #{a}, #{b}"
end

Backreferences in sub and gsub

String#sub and String#gsub now feature a syntax for backreferences, similar to Ruby’s. For example:

puts "hello world".gsub(/([aeiou])/, "*\\1*") # => "h*e*ll*o* w*o*rld"

To implement this, gsub does a quick check to see if the string has any backlash in it. If so, for every match it will scan the string for backreferences. The quick check would make existing code slower. However, most of the cases the replacement string is known at compile-time, so that check disappears in release mode, thanks to LLVM.

Custom separator and quote for CSV

The separator and quote field for parsing CSV can now be specified at construction time, thanks to jreinert:

require "csv"

string = <<-CSV
         name;value
         foo;bar
         CSV
CSV.parse(string, separator: ';') # => [["name", "value"], ["foo", "bar"]]

Random float

Now you can generate a random float between 0 and max, or between a given float range, thanks to AlexWayfer:

puts rand(1.5) # => 0.0369659
puts rand(1.5..2.5) # => 1.68439

Other changes

Be sure to read the full changelog, as there are more additions, small changes, bug fixes and optimizations.