🔎 Logic Programming

📖 What Is It?

Logic programming works by defining facts (things that are true) and rules (relationships between facts). Instead of telling the computer how to solve a problem, you give it information and ask questions — it figures out the answers itself.

Key characteristics:

Facts — statements that are true (e.g., "iron is a metal")
Rules — relationships that define new truths from existing facts (e.g., "if X is a metal, X can be smelted")
Queries — questions you ask the system (e.g., "can iron be smelted?")
You describe WHAT is true, and the computer works out the answer

🎮 Where It Is Used

Example	Why Logic?
Minecraft crafting system	The game has facts (wood + sticks = sword) and rules (if you have all ingredients, you can craft the item). The system answers: "Can this player craft a diamond pickaxe?" by checking facts.
Game AI / NPCs	NPC behaviour in WoW: IF player_near AND player_hostile THEN attack. Rules determine behaviour.
Databases / SQL	SQL queries are logic-based: "Find all players WHERE level > 50 AND guild = 'Alliance'"
Expert systems	Medical diagnosis systems: given symptoms (facts), apply rules to determine possible conditions

🐍 Experiment: Logic-Style in Python

🐍 Logic — Minecraft Crafting System

# LOGIC STYLE: define facts and rules, then query them

# FACTS: what materials are needed for each recipe
recipes = {
    "wooden_sword": ["wood", "stick"],
    "stone_pickaxe": ["stone", "stick"],
    "iron_helmet": ["iron", "iron", "iron"],
    "cake": ["milk", "sugar", "egg", "wheat"]
}

# FACTS: what the player currently has
inventory = ["wood", "stick", "iron", "iron", "sugar", "egg"]

# RULE: a player can craft an item IF they have ALL required materials
def can_craft(item_name, player_inv):
    if item_name not in recipes:
        return False
    needed = list(recipes[item_name])
    available = list(player_inv)
    for material in needed:
        if material in available:
            available.remove(material)
        else:
            return False
    return True

# QUERIES: ask the system questions
for item in recipes:
    result = can_craft(item, inventory)
    status = "YES" if result else "NO"
    print("Can craft", item + "?", status)
    if not result:
        print("  Missing:", [m for m in recipes[item]
              if recipes[item].count(m) > inventory.count(m)])

🔍 Why This Is Logic-Style

Facts are defined: recipes (what materials are needed) and inventory (what the player has)
A rule determines if crafting is possible: "if the player has all required materials"
We ask queries: "Can craft wooden_sword?" — the system works out the answer from the facts and rules
We did NOT tell the computer step-by-step how to search — we defined WHAT is true and let it figure it out

💡 Note on Logic Programming

True logic programming uses languages like Prolog. Python is not a logic language, but we can simulate the logic style — defining facts, rules, and queries. The key idea is: you declare what is true and ask questions, rather than giving step-by-step instructions.

✏️ In your own words, describe the key characteristics of logic programming: