Ruby/Language Basics/puts

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Array on righthand side for multiple args

puts "%s: %f" % ["pi", Math::PI]



Comparing Floating-Point Numbers

puts 1.8 + 0.1                                  # => 1.9
puts 1.8 + 0.1 == 1.9                           # => false
puts 1.8 + 0.1 > 1.9                            # => true



%d for decimal integers

puts "%d" % 10         # => "10": %d for decimal integers



Display a Message

puts "Hello from Ruby."



exponential with uppercase E

puts "%E" % 1234.567   # => "1.234567e+03": exponential with uppercase E



Field and precision combined

puts "%6.4g" % 123.456 # " 123.5": four significant digits in field six chars wide
puts "%3s" % "ruby"    # "ruby": string argument exceeds field width
puts "%3.3s" % "ruby"  # "rub": precision forces truncation of string



Field width

puts "%5s" % "<<<"     # "  <<<": right-justify in field five characters wide
puts "%-5s" % ">>>"    # ">>>  ": left-justify in field five characters wide
puts "%5d" % 123       # "  123": field is five characters wide
puts "%05d" % 123      # "00123": pad with zeros in field five characters wide



Float number Precision

puts "%.2f" % 123.456  # "123.46": two digits after decimal place
puts "%.2e" % 123.456  # "1.23e+02": two digits after decimal = three significant digits
puts "%.6e" % 123.456  # "1.234560e+02": note added zero
puts "%.4g" % 123.456  # "123.5": four significant digits



force exponential notation

puts "%e" % 1234.567   # => "1.234567e+03": force exponential notation



format a string with puts

#!/usr/bin/env ruby
puts "%s, %s!" % [ "Hello", "myValue" ]



format based string interpolation

#!/usr/bin/env ruby
hi = "Hello, %s"
puts hi % "myValue!" # => "Hello, myValue!"
puts hi % "people!" # => "Hello, people!"
puts hi % "universe!" # => "Hello, universe!"



full-length floating-point numbers

puts "%f" % 1234.567   # => "1234.567000": full-length floating-point numbers



Get the command line parameter

#!/usr/bin/env ruby
puts "Hello, #{ARGV[0]}!"



hexadecimal integers

puts "%x" % 10         # => "a": hexadecimal integers



Insert some output from a shell command

puts "Hey Matz, I"m running " + "ruby --version"



Multiple arguments to be formatted

puts args = ["Syntax Error", "test.rb", 20]  # An array of arguments
"%s: in "%s" line %d" % args    # => "Syntax Error: in "test.rb" line 20"



octal integers string format

puts "%o" % 10         # => "12": octal integers



Put two or more variables together with the + method:

hi = "Hello, "
person = "Matz!"
puts hi + person # => Hello, Matz!



Simple Arithmetic

puts 1.0 + 2.0
puts 2.0 * 3.0
puts 5.0 - 8.0
puts 9.0 / 2.0
# This is what the program returns:
3.0
6.0
-3.0
4.5



six significant digits

puts "%g" % 1234.567   # => "1234.57": six significant digits



uppercase hexadecimal integers

puts "%X" % 10         # => "A": uppercase hexadecimal integers



Use %f or %e depending on magnitude

puts "%g" % 1.23456E12 # => "1.23456e+12": Use %f or %e depending on magnitude



use parentheses

puts 5 * (12-8) + -15
puts 98 + (59872 / (13*8)) * -52