Editing Predicate Logic (section)

== <span style="color: #FFFFFF;">Applying</span> ==
'''Modeling 'The Database Query' (Translating English into Predicate Logic):'''
<syntaxhighlight lang="python">
def evaluate_predicate(domain, predicate_func, quantifier):
    """
    Simulates ∀ and ∃ logic.
    """
    results = [predicate_func(obj) for obj in domain]
    
    if quantifier == "ALL": # ∀
        return all(results)
    elif quantifier == "EXISTS": # ∃
        return any(results)
        
    return None

# World: [1, 2, 3, 4] | Predicate: "Is even?"
numbers = [1, 2, 3, 4]
is_even = lambda x: x % 2 == 0

# Check: "Are ALL numbers even?" (∀x Even(x))
print(f"∀x Even(x): {evaluate_predicate(numbers, is_even, 'ALL')}")
# Check: "Is there SOME number that is even?" (∃x Even(x))
print(f"∃x Even(x): {evaluate_predicate(numbers, is_even, 'EXISTS')}")
</syntaxhighlight>

; Logic Landmarks
: '''Begriffsschrift (1879)''' → Gottlob Frege's book that "Invented" modern predicate logic, often called the "Most important work in logic since Aristotle."
: '''Principia Mathematica (1910)''' → Russell and Whitehead's attempt to derive all of math from pure predicate logic (a massive task that took 2,000 pages).
: '''SQL (1974)''' → The standard language for databases, which is literally just "Predicate Logic in a Suit."
: '''Prolog (1972)''' → The first "Logic Programming Language," where you don't write "Steps," you just write "Facts and Rules" in predicate logic, and the computer finds the answer for you.
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