Power

Power is a curried constructor used to create a JS/JSON configuration object that represents an exponential operation.

const Power =
  (datatype = "Number") =>
  base =>
  exponent => ({
    tag: "Power",
    base,
    exponent,
    datatype,
  })
 
export default Power
 

The first parameter to Power determines the datatype of the return value of the division operation: Number (float) or Integer.

The second parameter is the base; the third is the exponent. Both are operations, which must eventually evaluate to values. The base will be raised to the exponent to produce the result.

The base and exponent operations (multiply, subtract, etc.) may be nested to any depth, but the bottom (leaf) nodes must return values. Values are injected with injectors.

Because Power is curried, we can simplify our code by partial application, for example, const Pow = Power("Integer"). This returns a function that takes the base and exponent operations and returns a Power configuration for working with integers.

See below for an example.

The power function

We pass our configuration object to composeOperators, which composes the operations and returns a single function. This function takes an optional argument and returns the result of the calculation as a Right, e.g., { right: 42 }, or a Left with an array of Error objects, { left: [Error] }.

const power = operation => (arg? => Either<Array<Error>, result>)

composeOperators works by recursing down through the operation object, calling the correct operator function based on the tag (e.g., "Power"), and composing the functions returned. composeOperators then returns this composed function. See composeOperators for a more detailed explanation.

The injectors are not called until this composed calculate function is run. Hence, evaluation is lazy: the values are not injected until the last moment.

See the injectors for a complete list of how values may be injected. See the list of operators for the full range of available mathematical operations.

Example

We use composeOperators to create a calculate function, passing it our Power operation object. We call the calculate function and pass it an (optional) argument to run our operation(s) and calculate the quotient.

Here our base operation is a nested multiplication operation of two constants (using Constant). Our exponent is also an operation that returns the argument passed to the composed function (using FromArgument).

Try leaving one of the numbers undefined to see an Error returned.