TypeScript Calculator

Demo (https://jomcode.github.io/tscalc/)

calculator:: input * state -> state

States

ZeroState

Input	Result	Next State
Zero	Nothing.	ZeroState
NonZeroDigit	Append digit to new accumulator.	AccumulatorState
Operation	If pending op, calculate and create next pending from input. Else create pending op.	ComputedState
Equals	Compute from pending op. No resulting pending ops created.	ComputedState
Clear	Nothing.	ZeroState

AccumulatorState

Input	Result	Next State
Zero	Append zero to accumulator.	AccumulatorState
NonZeroDigit	Append digit to accumulator.	AccumulatorState
Operation	If pending op, update display with OperationResult. If successful, create pending op.	ComputedState
Equals	Compute from pending op. No resulting pending ops created.	ComputedState
Clear	Clear any pending and go to ZeroState.	ZeroState

ComputedState

Input	Result	Next State
Zero	Go to ZeroState with current pending op if exists.	ZeroState
NonZeroDigit	Append digit to new accumulator. Keep pending op if exists.	AccumulatorState
Operation	Replace any pending op with new one from input.	ComputedState
Equals	Clear pending op.	ComputedState
Clear	Clear any pending and go to ZeroState.	ZeroState

ErrorState

Input	Result	Next State
All Except Clear	Nothing.	ErrorState
Clear	Clear any pending and go to ZeroState.	ZeroState

TODO

• generic tests corrections
• ng2 tests
• Either tests
• make tests more descriptive
• refactor tests to be less brittle
• decimal?
• negate?
• square rt?