Root

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

const Root =
  (datatype = "Number") =>
  radicand =>
  index => ({
    tag: "Root",
    radicand,
    index,
    datatype,
  })
 
export default Root
 

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

The second parameter is the radicand; the third is the index. Both are operations, which must eventually evaluate to values. The index determines the root: 2 for square root, 3 for cube root, etc.

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

Because Root is curried, we can simplify our code by partial application, for example, const R = Root("Number"). This returns a function that takes the radicand and index operations and returns a Root configuration for working with integers.

See below for an example.

The root 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 root = operation => (arg? => Either<Array<Error>, result>)

composeOperators works by recursing down through the operation object, calling the correct operator function radicandd on the tag (e.g., "Root"), 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 Root operation object. We call the calculate function and pass it an (optional) argument to run our operation(s) and calculate the quotient.

Here our radicand operation is a nested multiplication operation of three constants (using Constant). Our index 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.