Crystal type examples

add-generic-any-types.cr

def add(x : T, y : U) forall T, U
  x + y
end

p add(1, 2)
p add(0.1, 0.2)

add-generic-same-types.cr

def add(x : T, y : T) forall T
  x + y
end

p add(1, 2)
p add(0.1, 0.2)

add-overload.cr

# Originally I had this as add_ by accident and the add(1, 2) call converted
# the arguments to floats and called the other one.
def add(x : Int32, y : Int32)
  x + y
end

def add(x : Float64, y : Float64)
  x + y
end

p add(1, 2)
p add(0.1, 0.2)

add-separate.cr

def add_integers(x : Int32, y : Int32)
  x + y
end

def add_floats(x : Float64, y : Float64)
  x + y
end

p add_integers(1, 2)
p add_floats(0.1, 0.2)

arg.cr

def die(message)
  STDERR.puts "#{PROGRAM_NAME}: error: #{message}"
  exit 1
end

begin
  n = ARGV[0].to_i
  puts "#{n} squared is #{n**2}."
rescue IndexError
  die "too few arguments"
rescue ArgumentError
  die %[can't square "#{ARGV[0]}"]
end

arg2.cr

def die(message)
  STDERR.puts "#{PROGRAM_NAME}: error: #{message}"
  exit 1
end

arg = ARGV[0]?
puts "arg : #{typeof(arg)}"
die "too few arguments" if arg.nil?
puts "arg : #{typeof(arg)}"
n = arg.to_i?
puts "n : #{typeof(n)}"
die %[can't square #{ARGV[0]}] if n.nil?
puts "n : #{typeof(n)}"
puts "#{n} squared is #{n**2}."

argv.cr

answer = 42
p typeof(answer)
answer = ARGV[0] unless ARGV.empty?
p typeof(answer)
answer = 1.234 if answer.is_a?(Int32)
p typeof(answer)

dead.cr

x = 10

if false
  x = "hello"
  p x + 1
end

p typeof(x)

gets.cr

print "Enter a number to square: "
line = gets

if line.nil?
  puts "\nGot end-of-input."
  exit
end

n = line.to_i?
if n.nil?
  puts "I can't square that."
else
  puts "That squares to #{n**2}."
end

increment.cr

n = ARGV[0].to_u64
n += 1 if ENV.has_key?("INCREMENT")
puts "#{n} : #{typeof(n)}"

LICENSE

Copyright (c) 2020 Eliah Kagan <degeneracypressure@gmail.com>

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.

var.cr

if ARGV.empty?
  x = 5
  p typeof(x)
else
  x = ARGV[0]
  p typeof(x)
end

p typeof(x)