nanomath/src/complex/type.js

import {Complex} from './Complex.js'
import {Returns} from "#core/Type.js"
import {Any, match} from "#core/TypePatterns.js"
import {NumberT} from '#number/NumberT.js'

export const complex = [
   match(Any, (math, T) => {
      const z = math.zero(T)
      if (math.hasnan(T)) {
         const isnan = math.isnan.resolve([T])
         const compnan = math.nan(Complex(T))
         return Returns(Complex(T), r => {
            if (isnan(r)) return compnan
            return {re: r, im: z}
         })
      }
      return Returns(Complex(T), r => ({re: r, im: z}))
   }),
   match([Any, Any], (math, [T, U]) => {
      if (T !== U) {
         throw new RangeError(
            'mixed complex types disallowed '
               + `(real ${T}, imaginary ${U})`)
      }
      return Returns(Complex(T), (r, m) => ({re: r, im: m}))
   })
]

export const arg = match(
    Complex(NumberT), Returns(NumberT, z => Math.atan2(z.im, z.re)))