Booleans

Booleans in Lean

Lean's Bool type has two values: true and false (lowercase, unlike Haskell).

Logical operators:

• && — and
• || — or
• ! — not (prefix)

Comparison operators return Bool:

• ==, != — equality
• <, >, <=, >= — comparisons

#eval true && false    -- false
#eval true || false    -- true
#eval !true            -- false
#eval 5 > 3            -- true
#eval 10 == 10         -- true

Your Turn

Evaluate:

1. true && true
2. false || true
3. !false
4. 7 < 3