Logic

Control flow statements in Lua allow you to dictate the order in which instructions are executed, enabling decision-making and repetitive actions in your programs.

Control Flow Statements Overview

Statement	Description
if...then...else...end	Conditional statement that checks conditions from top to bottom. If a condition is true, it executes the corresponding block and ignores the rest.
while...do...end	A loop that repeatedly executes a block of code as long as the condition is true. The condition is checked before executing the block.
for...do...end	A loop that executes a block of code a specific number of times, controlled by the for statement.
repeat...until	A loop that repeatedly executes a block of code until a specified condition is true. The condition is checked after executing the block.

if Conditional Statement

The condition following if can be any expression. Lua treats false and nil as false, while everything else (including 0) is true. If the expression is true, the code block following then is executed; if false, the code block following else (if present) is executed.

Flowchart:

Example:

a = 100
b = 200

-- Check condition
if (a == 100) then
    -- Execute this block if the condition is true
    if (b == 200) then
        print("a 的值为:", a)  -- a 的值为: 100
        print("b 的值为:", b)  -- b 的值为: 200
    end
else
    -- Execute this block if the first condition is false
    print("a不等于100")
end

while Loop Control Statement

In a while loop, the condition is checked before executing the block of code. If the condition is true, the code block inside do is executed.

Flowchart:

Example:

a = 10
while (a < 20) do
    print("a 的值为:", a)  -- Outputs values from 10 to 19
    a = a + 1
end

for Loop Control Statement

The for loop syntax is as follows:

for var = exp1, exp2, exp3 do  
    <执行体>  
end

Here, var starts at exp1 and increments by exp3 (which can be negative or omitted, defaulting to 1) until var exceeds exp2.

Flowchart:

Example:

for i = 10, 1, -1 do
    print(i) -- Outputs values from 10 to 1
end

repeat Loop Control Statement

The repeat loop checks the condition after executing the block of code, meaning the block is executed at least once before the condition is evaluated.

Flowchart:

Example:

a = 10
repeat
    print("a的值为:", a) -- Outputs values from 10 to 15
    a = a + 1
until (a > 15)

These control flow statements provide the necessary structure to implement logic in your Lua programs, enabling complex decision-making and iterations.