Added tons of opcode documentation, changed license to ISC and a lot of file refactoring.

src/vm/arithmetic/add.c

@@ -1,3 +1,40 @@
+/**
+ * This file is part of the Fun programming language.
+ * https://hanez.org/project/fun/
+ *
+ * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the ISC license.
+ * https://opensource.org/license/isc-license-txt
+ */
+
+/**
+* @file add.c
+ * @brief Implements the OP_ADD opcode for arithmetic and string concatenation in the VM.
+ *
+ * This file handles the OP_ADD instruction, which performs addition or concatenation
+ * depending on the types of the operands:
+ * - Integers: Adds two integers.
+ * - Strings: Concatenates two strings.
+ * - Arrays: Concatenates two arrays.
+ *
+ * Behavior:
+ * - Pops two values from the stack.
+ * - Performs the operation based on the types of the operands.
+ * - Pushes the result back onto the stack.
+ *
+ * Error Handling:
+ * - Exits with an error if the operands are of incompatible types.
+ * - Exits with an error if memory allocation fails during string concatenation.
+ *
+ * Example:
+ * // Bytecode: OP_ADD
+ * // Stack before: [2, 3]
+ * // Stack after: [5]
+ *
+ * @author Johannes Findeisen
+ * @date 2025-10-16
+ */
+
 case OP_ADD: {
     Value b = pop_value(vm);
     Value a = pop_value(vm);

src/vm/arithmetic/div.c

@@ -1,3 +1,37 @@
+/**
+ * This file is part of the Fun programming language.
+ * https://hanez.org/project/fun/
+ *
+ * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the ISC license.
+ * https://opensource.org/license/isc-license-txt
+ */
+
+/**
+* @file div.c
+ * @brief Implements the OP_DIV opcode for integer division in the VM.
+ *
+ * This file handles the OP_DIV instruction, which performs integer division
+ * on two integer values popped from the stack and pushes the result back onto the stack.
+ *
+ * Behavior:
+ * - Pops two integer values from the stack.
+ * - Performs integer division (`a / b`).
+ * - Pushes the result back onto the stack.
+ *
+ * Error Handling:
+ * - Exits with an error if the operands are not integers.
+ * - Exits with an error if division by zero is attempted.
+ *
+ * Example:
+ * // Bytecode: OP_DIV
+ * // Stack before: [10, 2]
+ * // Stack after: [5]
+ *
+ * @author Johannes Findeisen
+ * @date 2025-10-16
+ */
+
 case OP_DIV: {
     Value b = pop_value(vm);
     Value a = pop_value(vm);

src/vm/arithmetic/mul.c

@@ -1,3 +1,36 @@
+/**
+ * This file is part of the Fun programming language.
+ * https://hanez.org/project/fun/
+ *
+ * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the ISC license.
+ * https://opensource.org/license/isc-license-txt
+ */
+
+/**
+* @file mul.c
+ * @brief Implements the OP_MUL opcode for integer multiplication in the VM.
+ *
+ * This file handles the OP_MUL instruction, which performs integer multiplication
+ * on two integer values popped from the stack and pushes the result back onto the stack.
+ *
+ * Behavior:
+ * - Pops two integer values from the stack.
+ * - Performs integer multiplication (`a * b`).
+ * - Pushes the result back onto the stack.
+ *
+ * Error Handling:
+ * - Exits with an error if the operands are not integers.
+ *
+ * Example:
+ * // Bytecode: OP_MUL
+ * // Stack before: [3, 4]
+ * // Stack after: [12]
+ *
+ * @author Johannes Findeisen
+ * @date 2025-10-16
+ */
+
 case OP_MUL: {
     Value b = pop_value(vm);
     Value a = pop_value(vm);

src/vm/arithmetic/sub.c

@@ -1,3 +1,36 @@
+/**
+ * This file is part of the Fun programming language.
+ * https://hanez.org/project/fun/
+ *
+ * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the ISC license.
+ * https://opensource.org/license/isc-license-txt
+ */
+
+/**
+* @file sub.c
+ * @brief Implements the OP_SUB opcode for integer subtraction in the VM.
+ *
+ * This file handles the OP_SUB instruction, which performs integer subtraction
+ * on two integer values popped from the stack and pushes the result back onto the stack.
+ *
+ * Behavior:
+ * - Pops two integer values from the stack.
+ * - Performs integer subtraction (`a - b`).
+ * - Pushes the result back onto the stack.
+ *
+ * Error Handling:
+ * - Exits with an error if the operands are not integers.
+ *
+ * Example:
+ * // Bytecode: OP_SUB
+ * // Stack before: [10, 4]
+ * // Stack after: [6]
+ *
+ * @author Johannes Findeisen
+ * @date 2025-10-16
+ */
+
 case OP_SUB: {
     Value b = pop_value(vm);
     Value a = pop_value(vm);