     ref.forDefault({
       isEqual: -> console.log(@); throw "NOT IMPLEMENTED"
     })
-    # Number
+
+    # Pi
     ref.forType(comps.pi, {
       isEqual: (buildIsEqual(comps.pi))
     })


    # Exponentiation
    ref.forType(comps.exponentiation, {
      isEqual: (buildIsEqual(comps.exponentiation)),
      _simpleIsEqual: (other)->
        ref.refine(@base()).isEqual(other.base()) and
          ref.refine(@power()).isEqual(other.power())
      })


    # Expression
    ref.forType(comps.expression, {
      isExpressionEqual: (other)->
        logger.info("isExpressionEqual", @unrefined(), other)
        if @is_error == other.is_error && @is_open == other.is_open
          if _(@expression).size() == _(other.expression).size()
            contains_unequal =
              _.chain(@expression).map((element, i)->
                ref.refine(element).isEqual(other.nth(i))
              ).contains(false).value()
            !contains_unequal
          else
            false
        else
          false

      isEqual: (other)->
        if other instanceof comps.expression
          @isExpressionEqual(other)
    })



    # Multiplication


    logger = logger_builder.build(stringify_objects: false)

    buildIsEqual = (for_type, additional_method=false)->
      isEqualFunction = (other, eq_calc)->
        same_type = eq_calc.saveFalseForReport((other instanceof for_type), @unrefined(), other,
          "Wrong types")
        if same_type
          if additional_method
            @[additional_method](other, eq_calc)
          else
            true
        else
          false
      logger.instrument(name: "buildIsEqual function", fn: isEqualFunction)
