عبارات if وelseif وelse

عبارة if الأساسية

local score = 85

if score >= 90 then
  print("A grade")
end

if score >= 60 then
  print("Passing")   -- prints
end

if 0 then
  print("0 is truthy!")  -- prints in Lua
end

if/elseif/else

local score = 75

if score >= 90 then
  print("A")
elseif score >= 80 then
  print("B")
elseif score >= 70 then
  print("C")   -- prints
elseif score >= 60 then
  print("D")
else
  print("F")
end

العوامل المنطقية في الشروط

local age = 25
local hasID = true

if age >= 18 and hasID then
  print("Entry allowed")
end

-- or for defaults
local name = nil
local display = name or "Guest"
print(display)   -- Guest

النمط الاصطلاحي للمشغّل الثلاثي باستخدام and/or

local x = 10
local label = (x > 5) and "big" or "small"
print(label)   -- big

-- Safe ternary function
local function ternary(cond, t, f)
  if cond then return t else return f end
end
print(ternary(false, "yes", "no"))  -- no

عبارات if المتداخلة

local loggedIn = true
local isAdmin = false

if loggedIn then
  if isAdmin then
    print("Admin dashboard")
  else
    print("User dashboard")  -- prints
  end
else
  print("Login required")
end

عبارات الحراسة

local function processAge(age)
  if type(age) ~= "number" then
    return nil, "age must be a number"
  end
  if age < 0 then
    return nil, "age cannot be negative"
  end
  -- happy path
  return math.floor(age)
end

print(processAge(25.7))   -- 25
print(processAge(-1))     -- nil  age cannot be negative

مقارنة القيم

print(1 == 1)      -- true
print(1 ~= 2)      -- true
print("abc" < "abd")  -- true (lexicographic)
print("10" == 10)  -- false (different types)

-- Safe nil check
local val = nil
if val == nil then
  print("no value")
end

تساوي السلاسل النصية

local s1 = "hello"
local s2 = "hel" .. "lo"

print(s1 == s2)     -- true (same content)
print(s1 == "Hello") -- false (case sensitive)

-- Check for empty string
local name = ""
if name == "" or name == nil then
  print("name is empty or nil")
end

مقارنة الجداول والدوال

local t1 = {1, 2, 3}
local t2 = {1, 2, 3}
local t3 = t1

print(t1 == t2)   -- false (different objects)
print(t1 == t3)   -- true (same reference)

local f1 = function() end
local f2 = function() end
print(f1 == f2)   -- false

الأنماط الاصطلاحية

-- assert pattern
local function sqrt(n)
  assert(n >= 0, "sqrt of negative")
  return math.sqrt(n)
end

-- Convert to boolean
local val = 42
local boolVal = not not val
print(boolVal)   -- true

-- Default parameter
local function greet(name)
  name = name or "World"
  print("Hello, " .. name)
end
greet()          -- Hello, World

تحقّق سريع

مراجعة: الشروط