Lua 關係運算子完整教學：比較邏輯與程式範例

關係運算子是程式設計中控制流程判斷的基礎。Lua 提供六種標準關係運算子，支援數值與字串比較，回傳布林值 true 或 false。

運算子總覽表

完整程式範例

a = 21
b = 10

if a == b then
    print("Line 1 - a is equal to b")
else
    print("Line 1 - a is not equal to b")
end

if a ~= b then
    print("Line 2 - a is not equal to b")
else
    print("Line 2 - a is equal to b")
end

if a < b then
    print("Line 3 - a is less than b")
else
    print("Line 3 - a is not less than b")
end

if a > b then
    print("Line 4 - a is greater than b")
else
    print("Line 4 - a is not greater than b")
end

-- 變更數值再測試
a = 5
b = 20

if a <= b then
    print("Line 5 - a is either less than or equal to b")
end

if b >= a then
    print("Line 6 - b is either greater than or equal to a")
end

執行結果

Line 1 - a is not equal to b
Line 2 - a is not equal to b
Line 3 - a is not less than b
Line 4 - a is greater than b
Line 5 - a is either less than or equal to b
Line 6 - b is either greater than or equal to a

重要特性提醒

• 型別敏感：Lua 中不同型別永不相等（1 == "1" 為 false）。
• 字串比較：依字典序（ASCII/UTF-8 碼值）逐字元比較。
• 表格/函數比較：== 僅比較參考位址，內容相同但不同實例仍為 false。
• ~= 是 Lua 特有的「不等於」寫法，不同於常見的 !=。