numbers.markdown

Fixnum

Concepts

• Numbers in Ruby are Objects
  • We can call methods on numbers
  • We can define methods on numbers
• Tricks with Numbers
  • Integer with Integer gives Integer
  • Integer with Float gives Float
  • Calling to_i on a String
• Truth
  • 0 is truthy
• Order of Operations

Essential Methods

• Core Ruby
  • Core Math Operators (+, -, *, /)
  • Modulo %
  • times
  • to_s / to_f
• With ActiveSupport
  • Date/Time Extensions: .hours, .days, .weeks, .months, .years, .ago/.until, .since/.from_now
  • Byte Extensions: .bytes, .kilobytes, .megabytes, .gigabytes
  • ordinalize

Float

Concepts

• Challenges when using Floats
  • Math is not precise
  • Formatting can be more difficult
• Alternatives
  • BigDecimal
  • Avoiding fractional components
• Using Kernel.format
• Whole Number Math vs. Fractional Math (ex: 1.0/2 vs 1/2)

Essential Methods

• Core Ruby
  • Core Math Operators (+, -, *, /)
  • ceil
  • to_i / floor
  • to_s

Maybe also:

• integer division returns an integer (someone is likely to run into 1/2 # => 0)
• operators with mixed integer / float return foat
• 0 is truthy in conditionals
• keep even spacing around operators (e.g. num1 *num2 is different from num1 * num2)
• operator precedence follows mathematical precedence
• operators are syntactic sugar for method invocation (IDK if you have a separate area where you're discussing operators)
• possibly 123 vs 0123 vs 0x123 vs 0b101 (that might be out of scope)

Thanks @JoshCheek, added most of them!