Minor code improvements.

src/Algebra.php

@@ -166,12 +166,14 @@ public static function factors(int $x): array
      * @param  number $a x² coefficient
      * @param  number $b x coefficient
      * @param  number $c constant coefficient
-     * @param  bool   $return_complex Whether to return complex numbers or NANs if imaginary roots
+     * @param  bool $return_complex Whether to return complex numbers or NANs if imaginary roots
      *
      * @return array  [x₁, x₂]           roots of the equation, or
      *                [NAN, NAN]         if discriminant is negative, or
      *                [Complex, Complex] if discriminant is negative and complex option is on or
      *                [x]                if a = 0 and formula isn't quadratics
+     *
+     * @throws Exception\IncorrectTypeException
      */
     public static function quadratic($a, $b, $c, bool $return_complex = false): array
     {
@@ -290,14 +292,16 @@ public static function discriminant($a, $b, $c)
      * z₂ = Complex conjugate; therefore, NAN
      * z₃ = Complex conjugate; therefore, NAN
      *
-     * @param  number $a₃  z³         coefficient
-     * @param  number $a₂  z²         coefficient
-     * @param  number $a₁  z          coefficient
-     * @param  number $a₀             constant coefficient
-     * @param  bool   $return_complex whether to return complex numbers
+     * @param  number $a₃ z³         coefficient
+     * @param  number $a₂ z²         coefficient
+     * @param  number $a₁ z          coefficient
+     * @param  number $a₀ constant coefficient
+     * @param  bool $return_complex whether to return complex numbers
      *
      * @return array of roots (three real roots, or one real root and two NANs because complex numbers not yet supported)
      *                        (If $a₃ = 0, then only two roots of quadratic equation)
+     *
+     * @throws Exception\IncorrectTypeException
      */
     public static function cubic($a₃, $a₂, $a₁, $a₀, bool $return_complex = false): array
     {
@@ -366,10 +370,12 @@ public static function cubic($a₃, $a₂, $a₁, $a₀, bool $return_complex =
      * @param  number $a₃ z³          coefficient
      * @param  number $a₂ z²          coefficient
      * @param  number $a₁ z           coefficient
-     * @param  number $a₀             constant coefficient
-     * @param  bool   $return_complex whether to return complex numbers
+     * @param  number $a₀ constant coefficient
+     * @param  bool $return_complex whether to return complex numbers
      *
      * @return array of roots
+     *
+     * @throws Exception\IncorrectTypeException
      */
     public static function quartic($a₄, $a₃, $a₂, $a₁, $a₀, bool $return_complex = false): array
     {

src/Functions/Arithmetic.php

@@ -14,7 +14,7 @@ class Arithmetic
      *
      * @return callable          Sum of the input functions
      */
-    public static function add(callable ...$args)
+    public static function add(callable ...$args): callable
     {
         $sum = function ($x, ... $args) {
             $function = 0;
@@ -37,7 +37,7 @@ public static function add(callable ...$args)
      *
      * @return callable          Product of the input functions
      */
-    public static function multiply(callable ...$args)
+    public static function multiply(callable ...$args): callable
     {
         $product = function ($x, ... $args) {
             $function = 1;

src/Functions/Piecewise.php

@@ -90,13 +90,13 @@ public function __construct(array $intervals, array $functions)
     * the corresponding function for that point in the domain, and then return
     * the function evaluated at that point. If no function is found, throw an Exception.
     *
-    * @param number $x₀ The value at which we are evaluating our piecewise function
+    * @param float $x₀ The value at which we are evaluating our piecewise function
     *
-    * @return number The specific function evaluated at $x₀
+    * @return float The specific function evaluated at $x₀
     *
     * @throws Exception\BadDataException if an interval cannot be found which contains our $x₀
     */
-    public function __invoke($x₀)
+    public function __invoke(float $x₀): float
     {
         $function = $this->getFunction($x₀);
         return $function($x₀);
@@ -107,14 +107,14 @@ public function __invoke($x₀)
     * the function that corresponds to that subinterval. If no subinterval is found
     * such that our input is contained within it, a false is returned.
     *
-    * @param number $x The value at which we are searching for a subinterval that
+    * @param float $x The value at which we are searching for a subinterval that
     *                  contains it, and thus has a corresponding function.
     *
     * @return callable Returns the function that contains $x in its domain
     *
     * @throws Exception\BadDataException if an interval cannot be found which contains our $x
     */
-    private function getFunction($x): callable
+    private function getFunction(float $x): callable
     {
         foreach ($this->intervals as $i => $interval) {
             $a     = $interval[0];
@@ -224,7 +224,7 @@ private function constructorPreconditions(array $intervals, array $functions)
      * @param  number $b
      * @param  number $lastA
      * @param  number $lastB
-     * @param  number $lastBOpen
+     * @param  bool   $lastBOpen
      * @param  bool   $aOpen
      * @param  bool   $bOpen
      *

src/Functions/Polynomial.php

@@ -293,6 +293,8 @@ public function integrate(): Polynomial
      * @param mixed $polynomial The polynomial or scaler we are adding to our current polynomial
      *
      * @return Polynomial The sum of our polynomial objects, also a polynomial object
+     *
+     * @throws Exception\IncorrectTypeException
      */
     public function add($polynomial): Polynomial
     {
@@ -327,6 +329,8 @@ public function add($polynomial): Polynomial
      * @param mixed $polynomial The polynomial or scaler we are subtracting from our current polynomial
      *
      * @return Polynomial The defference of our polynomial objects, also a polynomial object
+     *
+     * @throws Exception\IncorrectTypeException
      */
     public function subtract($polynomial): Polynomial
     {
@@ -346,6 +350,8 @@ public function subtract($polynomial): Polynomial
      * @param mixed $polynomial The polynomial or scaler we are multiplying with our current polynomial
      *
      * @return Polynomial The product of our polynomial objects, also a polynomial object
+     *
+     * @throws Exception\IncorrectTypeException
      */
     public function multiply($polynomial): Polynomial
     {
@@ -395,6 +401,8 @@ public function negate(): Polynomial
      * Closed form solutions only exist if the degree is less than 5
      *
      * @return array of roots
+     *
+     * @throws Exception\IncorrectTypeException
      */
     public function roots(): array
     {