While continuing your work at Instruments of Texas, there is progress being made on the Elixir implementation of the RPN calculator. Your team would like to be able to raise errors that are more specific than the generic errors provided by the standard library. You are doing some research, but you have decided to implement two new errors which implement the Exception Behaviour.
Dividing a number by zero produces an undefined result, which the team decides is best represented by an error.
DivisionByZeroError module to have the error message:
"division by zero occurred"
raise DivisionByZeroError # => ** (DivisionByZeroError) division by zero occurred
RPN calculators use a stack to keep track of numbers before they are added. The team represents this stack with a list of numbers (integer and floating-point), e.g.:
[3, 4.0]. Each operation needs a specific number of numbers on the stack in order to perform it's calculation. When there are not enough numbers on the stack, this is called a stack underflow error. Implement the
StackUnderflowError exception which provides a default message, and optional extra context
raise StackUnderflowError # => ** (StackUnderflowError) stack underflow occurred raise StackUnderflowError, "when dividing" # => ** (StackUnderflowError) stack underflow occurred, context: when dividing
divide/1 function which takes a stack (list of numbers) and:
RPNCalculator.Exception.divide() # => ** (StackUnderflowError) stack underflow occurred, context: when dividing RPNCalculator.Exception.divide([0, 100]) # => ** (DivisionByZeroError) division by zero occurred RPNCalculator.Exception.divide([4, 16]) # => 4
Note the order of the list is reversed!