`guard` macro for Crystal language

guard.cr

macro guard(*exprs, &block)
  {% if exprs.size == 1 %}
    ({{ exprs.first }}).tap do |v|
      {{ yield }} unless v
    end
  {% else %}
    {
      {% for expr in exprs %}
        ({{ expr }}),
      {% end %}
    }.tap do |conditions|
      {{ yield }} unless conditions.all?
    end
  {% end %}
end