diff --git a/.gitignore b/.gitignore
index 0dc139f..df7c548 100644
--- a/.gitignore
+++ b/.gitignore
@@ -129,6 +129,9 @@ dist
 # Stores VSCode versions used for testing VSCode extensions
 .vscode-test
 
+# Webstiorm
+.idea
+
 # yarn v2
 .yarn/cache
 .yarn/unplugged
diff --git a/src/Complex/all.ts b/src/Complex/all.ts
index b0ec237..3ff6311 100644
--- a/src/Complex/all.ts
+++ b/src/Complex/all.ts
@@ -1,3 +1,6 @@
 import * as Complex from './native.js'
+import * as complex from './arithmetic.js'
+
+export { complex }
 
 export {Complex}
diff --git a/src/Complex/arithmetic.ts b/src/Complex/arithmetic.ts
index 941a654..0987779 100644
--- a/src/Complex/arithmetic.ts
+++ b/src/Complex/arithmetic.ts
@@ -1,49 +1,54 @@
-import { Complex, complex_binary } from './type.js'
+import {Complex, complex_binary, FnComplexUnary} from './type.js'
+import type {
+    FnAbsSquare,
+    FnAdd,
+    FnAddReal,
+    FnConj, FnConservativeSqrt, FnDivide,
+    FnDivideByReal, FnIsReal, FnIsSquare,
+    FnMultiply, FnNaN, FnRe, FnReciprocal, FnSqrt,
+    FnSubtract,
+    FnUnaryMinus, FnZero
+} from '../interfaces/arithmetic'
 
 export const add =
    <T>(dep: {
-      add: (a: T, b: T) => T
-   }) =>
-      (w: Complex<T>, z: Complex<T>): Complex<T> =>
-         complex_binary(dep.add(w.re, z.re), dep.add(w.im, z.im))
+      add: FnAdd<T>
+   }): FnAdd<Complex<T>> =>
+      (w, z) => complex_binary(dep.add(w.re, z.re), dep.add(w.im, z.im))
 
 export const addReal =
    <T>(dep: {
-      addReal: (a: T, b: T) => T
-   }) =>
-      (z: Complex<T>, r: T): Complex<T> =>
-         complex_binary(dep.addReal(z.re, r), z.im)
+      addReal: FnAddReal<T, T>
+   }): FnAddReal<Complex<T>, T> =>
+      (z, r) => complex_binary(dep.addReal(z.re, r), z.im)
 
 export const unaryMinus =
    <T>(dep: {
-      unaryMinus: (z: T) => T
-   }) =>
-      (z: Complex<T>): Complex<T> =>
-         complex_binary(dep.unaryMinus(z.re), dep.unaryMinus(z.im))
+      unaryMinus: FnUnaryMinus<T>
+   }): FnUnaryMinus<Complex<T>> =>
+      (z) => complex_binary(dep.unaryMinus(z.re), dep.unaryMinus(z.im))
 
 export const conj =
    <T>(dep: {
-      unaryMinus: (z: T) => T,
-      conj: (z: T) => T
-   }) =>
-      (z: Complex<T>): Complex<T> =>
-         complex_binary(dep.conj(z.re), dep.unaryMinus(z.im))
+      unaryMinus: FnUnaryMinus<T>,
+      conj: FnConj<T>
+   }) : FnConj<Complex<T>> =>
+      (z) => complex_binary(dep.conj(z.re), dep.unaryMinus(z.im))
 
 export const subtract =
    <T>(dep: {
-      subtract: (a: T, b: T) => T
-   }) =>
-      (w: Complex<T>, z: Complex<T>): Complex<T> =>
-         complex_binary(dep.subtract(w.re, z.re), dep.subtract(w.im, z.im))
+      subtract: FnSubtract<T>
+   }): FnSubtract<Complex<T>> =>
+      (w, z) => complex_binary(dep.subtract(w.re, z.re), dep.subtract(w.im, z.im))
 
 export const multiply =
    <T>(dep: {
-      add: (a: T, b: T) => T,
-      subtract: (a: T, b: T) => T,
-      multiply: (a: T, b: T) => T,
-      conj: (z: T) => T
+      add: FnAdd<T>,
+      subtract: FnSubtract<T>,
+      multiply: FnMultiply<T>,
+      conj: FnConj<T>
    }) =>
-      (w: Complex<T>, z: Complex<T>): Complex<T> => {
+      (w, z) => {
          const mult = dep.multiply
          const realpart = dep.subtract(mult(w.re, z.re), mult(dep.conj(w.im), z.im))
          const imagpart = dep.add(mult(dep.conj(w.re), z.im), mult(w.im, z.re))
@@ -52,44 +57,42 @@ export const multiply =
 
 export const absquare =
    <T>(dep: {
-      add: (a: T, b: T) => T,
-      absquare: (z: T) => T
-   }) =>
-      (z: Complex<T>): T => dep.add(dep.absquare(z.re), dep.absquare(z.im))
+      add: FnAdd<T>,
+      absquare: FnAbsSquare<T, T>
+   }): FnAbsSquare<Complex<T>, T> =>
+      (z) => dep.add(dep.absquare(z.re), dep.absquare(z.im))
 
 export const divideByReal =
    <T>(dep: {
-      divideByReal: (a: T, b: T) => T
-   }) =>
-      (z: Complex<T>, r: T) =>
-         complex_binary(dep.divideByReal(z.re, r), dep.divideByReal(z.im, r))
+       divideByReal: FnDivideByReal<T, T>
+   }): FnDivideByReal<Complex<T>, T> =>
+      (z, r) => complex_binary(dep.divideByReal(z.re, r), dep.divideByReal(z.im, r))
 
 export const reciprocal =
    <T>(dep: {
-      conj: (z: Complex<T>) => Complex<T>,
-      absquare: (z: Complex<T>) => T,
-      divideByReal: (a: Complex<T>, b: T) => Complex<T>,
-      zero: (z: T) => T,
-   }) =>
-      (z: Complex<T>): Complex<T> => dep.divideByReal(dep.conj(z), dep.absquare(z))
+      conj: FnConj<Complex<T>>,
+      absquare: FnAbsSquare<Complex<T>, T>,
+      divideByReal: FnDivideByReal<Complex<T>, T>
+   }): FnReciprocal<Complex<T>> =>
+      (z) => dep.divideByReal(dep.conj(z), dep.absquare(z))
 
 export const divide =
    <T>(dep: {
-      multiply: (a: Complex<T>, b: Complex<T>) => Complex<T>,
-      reciprocal: (z: Complex<T>) => Complex<T>,
-   }) =>
-      (w: Complex<T>, z: Complex<T>) => dep.multiply(w, dep.reciprocal(z))
+      multiply: FnMultiply<Complex<T>>,
+      reciprocal: FnReciprocal<Complex<T>>,
+   }): FnDivide<Complex<T>> =>
+      (w, z) => dep.multiply(w, dep.reciprocal(z))
 
 export const complexSqrt =
    <T>(dep: {
-      conservativeSqrt: (a: T) => T,
-      isSquare: (a: T) => boolean,
-      complex: (a: T) => Complex<T>,
-      unaryMinus: (a: T) => T,
-      zero: (a: T) => T,
-      nan: (a: Complex<T>) => Complex<T>
+      conservativeSqrt: FnConservativeSqrt<T>,
+      isSquare: FnIsSquare<T>,
+      complex: FnComplexUnary<T>,
+      unaryMinus: FnUnaryMinus<T>,
+      zero: FnZero<T>,
+      nan: FnNaN<Complex<T>>
    }) =>
-      (r: T): Complex<T> => {
+      (r) => {
          if (dep.isSquare(r)) return dep.complex(dep.conservativeSqrt(r))
          const negative = dep.unaryMinus(r)
          if (dep.isSquare(negative)) {
@@ -104,17 +107,16 @@ export const complexSqrt =
 
 export const sqrt =
    <T>(dep: {
-      isReal: (z: Complex<T>) => boolean,
-      complexSqrt: (a: T) => Complex<T>,
-      conservativeSqrt: (a: T) => T,
-      absquare: (a: Complex<T>) => T,
-      addReal: (a: Complex<T>, b: T) => Complex<T>,
-      divideByReal: (a: Complex<T>, b: T) => Complex<T>,
-      add: (a: T, b: T) => T,
-      re: (a: Complex<T>) => T,
-
+      isReal: FnIsReal<Complex<T>>,
+      complexSqrt: FnSqrt<T>,
+      conservativeSqrt: FnConservativeSqrt<T>,
+      absquare: FnAbsSquare<Complex<T>, T>,
+      addReal: FnAddReal<Complex<T>, T>,
+      divideByReal: FnDivideByReal<Complex<T>, T>,
+      add: FnAdd<T>,
+      re: FnRe<Complex<T>, T>,
    }) =>
-      (z: Complex<T>) => {
+      (z: Complex<T>): Complex<T> | T => {
          if (dep.isReal(z)) return dep.complexSqrt(z.re)
          const myabs = dep.conservativeSqrt(dep.absquare(z))
          const num = dep.addReal(z, myabs)
diff --git a/src/Complex/predicate.ts b/src/Complex/predicate.ts
index 47365fb..557ea83 100644
--- a/src/Complex/predicate.ts
+++ b/src/Complex/predicate.ts
@@ -1,12 +1,14 @@
 import { Complex } from './type.js'
+import {FnEqual} from '../interfaces/relational'
+import {FnAdd, FnIsReal, FnIsSquare} from '../interfaces/arithmetic'
 
 export const isReal =
    <T>(dep: {
-      equal: (a: T, b: T) => boolean,
-      add: (a: T, b: T) => T,
-      isReal: (z: T) => boolean
-   }) =>
-      (z: Complex<T>) => dep.isReal(z.re) && dep.equal(z.re, dep.add(z.re, z.im))
+      equal: FnEqual<T>,
+      add: FnAdd<T>,
+      isReal: FnIsReal<T>
+   }): FnIsReal<Complex<T>> =>
+      (z) => dep.isReal(z.re) && dep.equal(z.re, dep.add(z.re, z.im))
 
 export const isSquare =
-   <T>(z: Complex<T>) => true // FIXME: not correct for Complex<bigint> once we get there
+   <T>(): FnIsSquare<Complex<T>> => (z) => true // FIXME: not correct for Complex<bigint> once we get there
diff --git a/src/Complex/relational.ts b/src/Complex/relational.ts
index 2621972..9807d71 100644
--- a/src/Complex/relational.ts
+++ b/src/Complex/relational.ts
@@ -1,7 +1,8 @@
 import { Complex } from './type.js'
+import {FnEqual} from '../interfaces/relational'
 
 export const equal =
    <T>(dep: {
-      equal: (a: T, b: T) => boolean
-   }) =>
-      (w: Complex<T>, z: Complex<T>): boolean => dep.equal(w.re, z.re) && dep.equal(w.im, z.im)
+      equal: FnEqual<T>
+   }): FnEqual<Complex<T>> =>
+      (w, z) => dep.equal(w.re, z.re) && dep.equal(w.im, z.im)
diff --git a/src/Complex/type.ts b/src/Complex/type.ts
index 50a231f..3b4e82d 100644
--- a/src/Complex/type.ts
+++ b/src/Complex/type.ts
@@ -1,6 +1,7 @@
 import {
    joinTypes, typeOfDependency, Dependency,
 } from '../core/Dispatcher.js'
+import type {FnNaN, FnOne, FnRe, FnZero} from '../interfaces/arithmetic.js'
 
 export type Complex<T> = { re: T; im: T; }
 
@@ -8,7 +9,7 @@ export const Complex_type = {
    test: <T>(dep: { testT: (z: unknown) => z is T }) =>
       (z: unknown): z is Complex<T> =>
          typeof z === 'object' && z != null && 're' in z && 'im' in z
-         && dep.testT(z.re) && dep.testT(z.im),
+         && dep.testT(z['re']) && dep.testT(z['im']),
    infer: (dep: typeOfDependency) =>
       (z: Complex<unknown>) => joinTypes(dep.typeOf(z.re), dep.typeOf(z.im)),
    from: {
@@ -19,36 +20,39 @@ export const Complex_type = {
    }
 }
 
+export type FnComplexUnary<T> = (t: T) => Complex<T>
+
 export const complex_unary =
    <T>(dep: {
-      zero: (z: T) => Complex<T>
-   }) =>
-      (t: T) => ({ re: t, im: dep.zero(t) })
+      zero: FnZero<T>
+   }): FnComplexUnary<T> =>
+      (t) => ({ re: t, im: dep.zero(t) })
 
-export const complex_binary =
-   <T>(t: T, u: T): Complex<T> => ({ re: t, im: u })
+export type FnComplexBinary<T> = (re: T, im: T) => Complex<T>
+
+export const complex_binary = <T>(t: T, u: T): Complex<T> => ({ re: t, im: u })
 
 export const zero =
    <T>(dep: {
-      zero: (z: T) => T
-   }) =>
-      (z: Complex<T>): Complex<T> => complex_binary(dep.zero(z.re), dep.zero(z.im))
+      zero: FnZero<T>
+   }): FnZero<Complex<T>> =>
+      (z) => complex_binary(dep.zero(z.re), dep.zero(z.im))
 
 export const one =
    <T>(dep: {
-      zero: (z: T) => T,
-      one: (z: T) => T
-   }) =>
-      (z: Complex<T>): Complex<T> => complex_binary(dep.one(z.re), dep.zero(z.im))
+      zero: FnZero<T>,
+      one: FnOne<T>
+   }): FnOne<Complex<T>> =>
+      (z) => complex_binary(dep.one(z.re), dep.zero(z.im))
 
 export const nan =
    <T>(dep: {
-      nan: (z: T) => T
-   }) =>
-      (z: Complex<T>): Complex<T> => complex_binary(dep.nan(z.re), dep.nan(z.im))
+      nan: FnNaN<T>
+   }): FnNaN<Complex<T>> =>
+      (z) => complex_binary(dep.nan(z.re), dep.nan(z.im))
 
 export const re =
    <T>(dep: {
-      re: (z: T) => T
-   }) =>
-      (z: Complex<T>): T => dep.re(z.re)
+      re: FnRe<T,T>
+   }): FnRe<Complex<T>, T> =>
+      (z) => dep.re(z.re)
diff --git a/src/generic/arithmetic.ts b/src/generic/arithmetic.ts
index 99a7aab..a1379df 100644
--- a/src/generic/arithmetic.ts
+++ b/src/generic/arithmetic.ts
@@ -1,5 +1,7 @@
+import type { FnMultiply, FnSquare } from "../interfaces/arithmetic"
+
 export const square =
   <T>(dep: {
-    multiply: (x: T, y: T) => T
-  }) =>
-    (z: T): T => dep.multiply(z, z)
+    multiply: FnMultiply<T>
+  }): FnSquare<T> =>
+    (z) => dep.multiply(z, z)
diff --git a/src/interfaces/arithmetic.ts b/src/interfaces/arithmetic.ts
new file mode 100644
index 0000000..91b59bf
--- /dev/null
+++ b/src/interfaces/arithmetic.ts
@@ -0,0 +1,28 @@
+// shared interfaces
+
+import { Complex } from "../Complex/type"
+
+// Note: right now I've added an 'Fn*' prefix,
+// so it is clear that the type hold a function type definition
+// This is not necessary though, it is just a naming convention.
+export type FnAdd<T> = (a: T, b: T) => T
+export type FnAddReal<T, U> = (a: T, b: U) => T
+export type FnUnaryMinus<T> = (a: T) => T
+export type FnConj<T> = (a: T) => T
+export type FnSubtract<T> = (a: T, b: T) => T
+export type FnMultiply<T> = (a: T, b: T) => T
+export type FnAbsSquare<T, U> = (a: T) => U
+export type FnReciprocal<T> = (a: T) => T
+export type FnDivide<T> = (a: T, b: T) => T
+export type FnDivideByReal<T, U> = (a: T, b: U) => T
+export type FnConservativeSqrt<T> = (a: T) => T
+export type FnSqrt<T> = (a: T) => T | Complex<T>
+export type FnSquare<T> = (z: T) => T
+
+export type FnIsReal<T> = (a: T) => boolean
+export type FnIsSquare<T> = (a: T) => boolean
+
+export type FnZero<T> = (a: T) => T
+export type FnOne<T> = (a: T) => T
+export type FnNaN<T> = (a: T) => T
+export type FnRe<T, U> = (a: T) => U
diff --git a/src/interfaces/relational.ts b/src/interfaces/relational.ts
new file mode 100644
index 0000000..2865f77
--- /dev/null
+++ b/src/interfaces/relational.ts
@@ -0,0 +1,3 @@
+
+export type FnEqual<T> = (a: T, b: T) => boolean
+export type FnUnequal<T> = (a: T, b: T) => boolean
diff --git a/src/numbers/arithmetic.ts b/src/numbers/arithmetic.ts
index 499a942..7142797 100644
--- a/src/numbers/arithmetic.ts
+++ b/src/numbers/arithmetic.ts
@@ -1,24 +1,25 @@
 import { Config } from '../core/Config.js'
-import type { Complex } from '../Complex/type.js'
+import type { FnComplexBinary } from '../Complex/type.js'
+import { FnAdd, FnConj, FnSubtract, FnUnaryMinus, FnMultiply, FnAbsSquare, FnReciprocal, FnDivide, FnConservativeSqrt, FnSqrt } from '../interfaces/arithmetic.js'
 
-export const add = (a: number, b: number): number => a + b
+export const add: FnAdd<number> = (a, b) => a + b
 export const addReal = add
-export const unaryMinus = (a: number): number => -a
-export const conj = (a: number): number => a
-export const subtract = (a: number, b: number): number => a - b
-export const multiply = (a: number, b: number): number => a * b
-export const absquare = (a: number): number => a * a
-export const reciprocal = (a: number): number => 1 / a
-export const divide = (a: number, b: number): number => a / b
+export const unaryMinus: FnUnaryMinus<number> = (a) => -a
+export const conj: FnConj<number> = (a) => a
+export const subtract: FnSubtract<number> = (a, b) => a - b
+export const multiply: FnMultiply<number> = (a, b) => a * b
+export const absquare: FnAbsSquare<number, number> = (a) => a * a
+export const reciprocal: FnReciprocal<number> = (a) => 1 / a
+export const divide: FnDivide<number> = (a, b) => a / b
 export const divideByReal = divide
 
-export const conservativeSqrt = (a: number): number => isNaN(a) ? NaN : Math.sqrt(a)
+export const conservativeSqrt: FnConservativeSqrt<number> = (a) => isNaN(a) ? NaN : Math.sqrt(a)
 
 export const sqrt =
    (dep: {
       config: Config,
-      complex: (re: number, im: number) => Complex<number>
-   }): (a: number) => number | Complex<number> => {
+      complex: FnComplexBinary<number>
+   }): FnSqrt<number> => {
       if (dep.config.predictable || !dep.complex) return conservativeSqrt
       return a => {
          if (isNaN(a)) return NaN
diff --git a/src/numbers/predicate.ts b/src/numbers/predicate.ts
index 483b103..4015c55 100644
--- a/src/numbers/predicate.ts
+++ b/src/numbers/predicate.ts
@@ -1,2 +1,4 @@
-export const isReal = (a: number) : boolean => true
-export const isSquare = (a: number) : boolean => a >= 0
+import type { FnIsReal, FnIsSquare } from "../interfaces/arithmetic"
+
+export const isReal: FnIsReal<number> = (a) => true
+export const isSquare: FnIsSquare<number> = (a)  => a >= 0
diff --git a/src/numbers/relational.ts b/src/numbers/relational.ts
index dac949a..ae9a63d 100644
--- a/src/numbers/relational.ts
+++ b/src/numbers/relational.ts
@@ -1,11 +1,12 @@
 import { Config } from '../core/Config.js'
+import type { FnEqual, FnUnequal } from '../interfaces/relational.js'
 
 const DBL_EPSILON = Number.EPSILON || 2.2204460492503130808472633361816E-16
 
 export const equal =
    (dep: {
       config: Config
-   }) => (x: number, y: number): boolean => {
+   }): FnEqual<number> => (x, y) => {
       const eps = dep.config.epsilon
       if (eps === null || eps === undefined) return x === y
       if (x === y) return true
@@ -21,6 +22,6 @@ export const equal =
    }
 
 export const unequal = (dep: {
-   equal: (x: number, y: number) => boolean
-}) =>
-   (x: number, y: number): boolean => !dep.equal(x, y)
+   equal: FnEqual<number>
+}): FnUnequal<number> =>
+   (x, y) => !dep.equal(x, y)
diff --git a/src/numbers/type.ts b/src/numbers/type.ts
index 46fbf6f..77336ef 100644
--- a/src/numbers/type.ts
+++ b/src/numbers/type.ts
@@ -1,10 +1,12 @@
+import type { FnNaN, FnOne, FnZero, FnRe } from "../interfaces/arithmetic"
+
 export const number_type = {
    before: ['Complex'],
    test: (n: unknown): n is number => typeof n === 'number',
    from: { string: (s: string) => +s }
 }
 
-export const zero = (a: number): number => 0
-export const one = (a: number): number => 1
-export const nan = (a: number): number => NaN
-export const re = (a: number): number => a
+export const zero: FnZero<number> = (a) => 0
+export const one: FnOne<number> = (a) => 1
+export const nan: FnNaN<number> = (a) => NaN
+export const re: FnRe<number, number> = (a) => a