Macro that performs chained comparison using operators like < and combinations using and or, and not.

examples

Examples

Chained comparison:

  iex> import CompareChain
  iex> compare?(1 < 2 < 3)
  true

Comparisons joined by logical operators:

  iex> import CompareChain
  iex> compare?(1 >= 2 >= 3 or 4 >= 5 >= 6)
  false

notes

Notes

You must include at least one comparison like < in your expression. Failing to do so will result in a compile time error.

Including a struct in the expression will result in a warning. You probably want to use compare?/2 instead.

Similar to compare?/1 except you can provide a module that defines a compare/2 for semantic comparisons.

This is like how you can provide a module as the second argument to Enum.sort/2.

examples

Examples

Basic comparison (note how a < b == false natively because of structural comparison):

  iex> import CompareChain
  iex> a = ~D[2017-03-31]
  iex> b = ~D[2017-04-01]
  iex> a < b
  false
  iex> compare?(a < b, Date)
  true

Chained comparison:

  iex> import CompareChain
  iex> a = ~D[2017-03-31]
  iex> b = ~D[2017-04-01]
  iex> c = ~D[2017-04-02]
  iex> compare?(a < b < c, Date)
  true

Comparisons joined by logical operators:

  iex> import CompareChain
  iex> a = ~T[15:00:00]
  iex> b = ~T[16:00:00]
  iex> c = ~T[17:00:00]
  iex> compare?(a < b and b > c, Time)
  false

More complex expressions:

  iex> import CompareChain
  iex> compare?(%{a: ~T[16:00:00]}.a <= ~T[17:00:00], Time)
  true

Custom module:

  iex> import CompareChain
  iex> defmodule AlwaysGreaterThan do
  iex>   def compare(_left, _right), do: :gt
  iex> end
  iex> compare?(1 > 2 > 3, AlwaysGreaterThan)
  true

notes

Notes

You must include at least one comparison like < in your expression. Failing to do so will result in a compile time error.