add table of contents and group api reference by topic

docs/api_reference.md

@@ -1,9 +1,48 @@
-## PHP `Option` Type Documentation
+# PHP `Option` Type Documentation
 
-The `Option` type in PHP is designed to handle the presence or absence of a value explicitly as part of its state. 
+The `Option` type in PHP is designed to handle the presence or absence of a value explicitly as part of its state.
 This allows developers to write more robust code by avoiding common errors like type errors and undefined indices.
 
-### **`some(mixed $value): self`**
+_Table of Contents:_
+
+- Creating an Option
+  - [some](#optionsomemixed-value-self)
+  - [none](#optionnone-self)
+  - [from](#optionfrommixed-value-self)
+  - [clone](#optionclone-self)
+- Querying the variant
+  - [isSome](#optionissome-bool)
+  - [isNone](#optionisnone-bool)
+- Extracting the contained value
+  - [expect](#optionexpectstring-message-mixed)
+  - [unwrap](#optionunwrap-mixed)
+  - [unwrapOr](#optionunwrapormixed-default-mixed)
+  - [unwrapOrElse](#optionunwraporelsecallable-fn-mixed)
+  - [unwrapOrThrow](#optionunwraporthrowthrowable-error-mixed)
+  - [flatten](#optionflatten-self)
+- Transforming contained values
+  - [match](#optionmatchcallable-some-callable-none-mixed)
+  - [map](#optionmapcallable-fn-self)
+  - [mapOr](#optionmaporcallable-fn-mixed-default-mixed)
+  - [mapOrElse](#optionmaporelsecallable-fn-callable-default-mixed)
+  - [andThen](#optionandthencallable-fn-self)
+  - [filter](#optionfiltercallable-predicate-self)
+- Boolean operators
+  - [or](#optionorself-option-self)
+  - [orElse](#optionorelsecallable-fn-self)
+  - [xor](#optionxorself-option-self)
+  - [and](#optionandself-option-self)
+- Iterating over `Option`
+  - [iterate](#optioniterate-arrayiterator)
+- Comparison operators
+  - [equals](#optionequalsself-option-bool)
+- Shortcut functions
+  - [some](#somemixed-value-option)
+  - [none](#none-option)
+
+## Creating an `Option`
+
+### **`Option::some(mixed $value): self`**
 
 Creates an `Option` instance containing a non-null value. If `null` is passed, a `LogicException` is thrown.
 
@@ -14,7 +53,7 @@ echo $opt->unwrap(); // Outputs: 10
 Option::some(null); // Throws LogicException
 ```
 
-### **`none(): self`**
+### **`Option::none(): self`**
 
 Creates an `Option` instance representing the absence of a value (i.e., `None`).
 
@@ -23,7 +62,7 @@ $opt = Option::none();
 echo $opt->isNone(); // Outputs: true
 ```
 
-### **`from(mixed $value): self`**
+### **`Option::from(mixed $value): self`**
 
 Converts a value to an `Option`, making it `None` if the original value is `null`, otherwise `Some`.
 
@@ -34,7 +73,19 @@ echo $some->isSome(); // Outputs: true
 echo $none->isNone(); // Outputs: true
 ```
 
-### **`isSome(): bool`**
+### **`Option::clone(): self`**
+
+Creates a copy of the option. Useful for preserving immutability when needed.
+
+```php
+$x = Option::some(2);
+$y = $x->clone();
+echo $y->unwrap(); // Outputs: 2
+```
+
+## Querying the variant
+
+### **`Option::isSome(): bool`**
 
 Checks if the option is a `Some` value.
 
@@ -43,7 +94,7 @@ $opt = Option::some(10);
 echo $opt->isSome(); // Outputs: true
 ```
 
-### **`isNone(): bool`**
+### **`Option::isNone(): bool`**
 
 Checks if the option is a `None` value.
 
@@ -52,25 +103,9 @@ $opt = Option::none();
 echo $opt->isNone(); // Outputs: true
 ```
 
-### **`match(callable $some, callable $none): mixed`**
-
-Applies a function to the contained value if it is `Some`, otherwise applies another function.
-
-```php
-$x = Option::some(2);
-echo $x->match(
-    some: fn ($v) => $v * 2, 
-    none: fn () => 0,
-); // Outputs: 4
-
-$x = Option::none();
-echo $x->match(
-    some: fn ($v) => $v * 2, 
-    none: fn () => 0,
-); // Outputs: 0
-```
+## Extracting the contained value
 
-### **`expect(string $message): mixed`**
+### **`Option::expect(string $message): mixed`**
 
 Returns the contained value if it is `Some`; otherwise, throws a `LogicException` with a custom message.
 
@@ -82,7 +117,7 @@ $opt = Option::none();
 echo $opt->expect('A number.'); // Throws LogicException with custom message
 ```
 
-### **`unwrap(): mixed`**
+### **`Option::unwrap(): mixed`**
 
 Returns the contained value if it is `Some`; otherwise, throws a `LogicException`.
 
@@ -94,7 +129,7 @@ $opt = Option::none();
 echo $opt->unwrap(); // Throws LogicException
 ```
 
-### **`unwrapOr(mixed $default): mixed`**
+### **`Option::unwrapOr(mixed $default): mixed`**
 
 Returns the contained value if it is `Some`; otherwise, returns a provided default value.
 
@@ -106,7 +141,7 @@ $opt = Option::none();
 echo $opt->unwrapOr(5); // Outputs: 5
 ```
 
-### **`unwrapOrElse(callable $fn): mixed`**
+### **`Option::unwrapOrElse(callable $fn): mixed`**
 
 Returns the contained value if it is `Some`; otherwise, computes a value using a provided callable.
 
@@ -118,7 +153,7 @@ $opt = Option::none();
 echo $opt->unwrapOrElse(fn () => 5); // Outputs: 5
 ```
 
-### **`unwrapOrThrow(\Throwable $error): mixed`**
+### **`Option::unwrapOrThrow(\Throwable $error): mixed`**
 
 Returns the contained value if it is `Some`; otherwise, throws the provided throwable error.
 
@@ -130,7 +165,39 @@ $opt = Option::none();
 echo $opt->unwrapOrThrow(new \Exception("No value!")); // Throws Exception
 ```
 
-### **`map(callable $fn): self`**
+### **`Option::flatten(): self`**
+
+Converts from `Option<Option<T>>` to `Option<T>`. Useful for unwrapping nested options.
+
+```php
+$x = Option::some(Option::some(2));
+echo $x->flatten()->unwrap(); // Outputs: 2
+
+$x = Option::some(Option::none());
+echo $x->flatten()->isNone(); // Outputs: true
+```
+
+## Transforming contained values
+
+### **`Option::match(callable $some, callable $none): mixed`**
+
+Applies a function to the contained value if it is `Some`, otherwise applies another function.
+
+```php
+$x = Option::some(2);
+echo $x->match(
+    some: fn ($v) => $v * 2, 
+    none: fn () => 0,
+); // Outputs: 4
+
+$x = Option::none();
+echo $x->match(
+    some: fn ($v) => $v * 2, 
+    none: fn () => 0,
+); // Outputs: 0
+```
+
+### **`Option::map(callable $fn): self`**
 
 Transforms the contained value by applying a function if it is `Some`; returns `None` if it is `None`.
 
@@ -144,7 +211,7 @@ $result = $opt->map(fn ($x) => $x * 2);
 echo $result->isNone(); // Outputs: true
 ```
 
-### **`mapOr(callable $fn, mixed $default): mixed`**
+### **`Option::mapOr(callable $fn, mixed $default): mixed`**
 
 Applies a function to the contained value if it is `Some`, otherwise returns a default value.
 
@@ -156,7 +223,7 @@ $opt = Option::none();
 echo $opt->mapOr(fn ($x) => $x * 2, 0); // Outputs: 0
 ```
 
-### **`mapOrElse(callable $fn, callable $default): mixed`**
+### **`Option::mapOrElse(callable $fn, callable $default): mixed`**
 
 Applies a function to the contained value if it is `Some`, otherwise computes the default using another callable.
 
@@ -168,7 +235,38 @@ $opt = Option::none();
 echo $opt->mapOrElse(fn ($x) => $x * 2, fn () => 0); // Outputs: 0
 ```
 
-### **`or(self $option): self`**
+### **`Option::andThen(callable $fn): self`**
+
+Applies a function to the contained value if it is `Some`, otherwise returns `None`. This is also known as flatmap
+in other languages.
+
+```php
+$x = Option::some(2);
+$result = $x->andThen(fn ($value) => Option::some($value * 2));
+echo $result->unwrap(); // Outputs: 4
+
+$x = Option::none();
+$result = $x->andThen(fn ($value) => Option::some($value * 2));
+echo $result->isNone(); // Outputs: true
+```
+
+### **`Option::filter(callable $predicate): self`**
+
+Returns `Some` if the option is `Some` and the predicate returns `true`; otherwise, returns `None`.
+
+```php
+$isEven = fn ($x) => $x % 2 === 0;
+
+$x = Option::some(4);
+echo $x->filter($isEven)->isSome(); // Outputs: true
+
+$x = Option::some(5);
+echo $x->filter($isEven)->isNone(); // Outputs: true
+```
+
+## Boolean operators
+
+### **`Option::or(self $option): self`**
 
 Returns the option itself if it is `Some`, otherwise returns the provided option.
 
@@ -181,7 +279,7 @@ $x = Option::none();
 echo $x->or($y)->unwrap(); // Outputs: 3
 ```
 
-### **`orElse(callable $fn): self`**
+### **`Option::orElse(callable $fn): self`**
 
 Returns the option itself if it is `Some`, otherwise calls a callable to provide an option.
 
@@ -194,7 +292,7 @@ $x = Option::none();
 echo $x->orElse(fn () => $y)->unwrap(); // Outputs: 3
 ```
 
-### **`xor(self $option): self`**
+### **`Option::xor(self $option): self`**
 
 Returns `Some` if exactly one of the options is `Some`, otherwise returns `None`.
 
@@ -207,7 +305,7 @@ $x = Option::none();
 echo $x->xor($y)->unwrap(); // Outputs: 3
 ```
 
-### **`and(self $option): self`**
+### **`Option::and(self $option): self`**
 
 Returns the provided option if the original option is `Some`, otherwise returns `None`.
 
@@ -220,22 +318,9 @@ $x = Option::none();
 echo $x->and($y)->isNone(); // Outputs: true
 ```
 
-### **`andThen(callable $fn): self`**
-
-Applies a function to the contained value if it is `Some`, otherwise returns `None`. This is also known as flatmap 
-in other languages.
-
-```php
-$x = Option::some(2);
-$result = $x->andThen(fn ($value) => Option::some($value * 2));
-echo $result->unwrap(); // Outputs: 4
-
-$x = Option::none();
-$result = $x->andThen(fn ($value) => Option::some($value * 2));
-echo $result->isNone(); // Outputs: true
-```
+## Iterating over `Option`
 
-### **`iterate(): \ArrayIterator`**
+### **`Option::iterate(): \ArrayIterator`**
 
 Provides an iterator over the contained value if it is `Some`, otherwise an empty iterator.
 
@@ -251,21 +336,9 @@ foreach ($x->iterate() as $v) {
 }
 ```
 
-### **`filter(callable $predicate): self`**
+## Comparison operators
 
-Returns `Some` if the option is `Some` and the predicate returns `true`; otherwise, returns `None`.
-
-```php
-$isEven = fn ($x) => $x % 2 === 0;
-
-$x = Option::some(4);
-echo $x->filter($isEven)->isSome(); // Outputs: true
-
-$x = Option::some(5);
-echo $x->filter($isEven)->isNone(); // Outputs: true
-```
-
-### **`equals(self $option): bool`**
+### **`Option::equals(self $option): bool`**
 
 Compares two options for equality. Returns `true` if both are `None` or if both are `Some` with equal values.
 
@@ -279,28 +352,6 @@ $y = Option::none();
 echo $x->equals($y); // Outputs: true
 ```
 
-### **`flatten(): self`**
-
-Converts from `Option<Option<T>>` to `Option<T>`. Useful for unwrapping nested options.
-
-```php
-$x = Option::some(Option::some(2));
-echo $x->flatten()->unwrap(); // Outputs: 2
-
-$x = Option::some(Option::none());
-echo $x->flatten()->isNone(); // Outputs: true
-```
-
-### **`clone(): self`**
-
-Creates a copy of the option. Useful for preserving immutability when needed.
-
-```php
-$x = Option::some(2);
-$y = $x->clone();
-echo $y->unwrap(); // Outputs: 2
-```
-
 ## Shortcut Functions
 
 ### **`some(mixed $value): Option`**