Use examples to learn about Lua (2)-Lua Process Control

1. Use of functions

The following program demonstrates how to use functions and local variables in Lua.

Example e02.lua

 　　-- functions　　function pythagorean(a, b)　　local c2 = a^2 + b^2　　return sqrt(c2)　　end　　print(pythagorean(3,4))

Running result

5

Program description

In Lua, The Function Definition Format is:

Function Name (parameter)

...

End

Unlike Pascal, end does not need to be paired with begin. You only need to end the function.

In this example, the function is used to obtain the diagonal side of a right triangle and obtain the length of the oblique side. parameters a and B indicate the length of the right side, respectively,

The local variable is defined in the function to store the square of the oblique edge. It is the same as the C language and defined in the function.

The code will not be executed directly, and will be executed only when the main program is called.

Local indicates defining a local variable. If the local variable is not added, C2 is a global variable, and the local scope

Is between the end of the innermost layer and the matched keywords, such as if... end, while... end. Global variable

The scope is the whole program.

2. Loop statements

Example e03.lua

 　　-- Loops　　for i=1,5 do　　print("i is now " .. i)　　end

Running result

I is now 1

I is now 2

I is now 3

I is now 4

I is now 5

Program description

Here we use the for statement.

For variable = parameter 1, parameter 2, parameter 3 do

Loop body

End

The variable takes parameter 3 as the step, and changes from parameter 1 to parameter 2.

For example:

For I = 1, F (x) Do print (I) End

For I = 10, 1,-1 do print (I) End

In Print ("I is now" .. I), we use..., which is used to connect two strings,

Even if I try to see what I mentioned in (1), I don't know if you have answered correctly.

Although I is an integer here, Lua will automatically convert it into a string type during processing, without worrying about it.

3. Condition branch statement

Example e04.lua

 　　-- Loops and conditionals　　for i=1,5 do　　print(“i is now “ .. i)　　if i < 2 then　　print(“small”)　　elseif i < 4 then　　print(“medium”)　　else　　print(“big”)　　end　　end

Running result

I is now 1

Small

I is now 2

Medium

I is now 3

Medium

I is now 4

Big

I is now 5

Big

Program description

If else is easy to use, similar to the C language, but note that the entire if only needs an end,

Even if multiple elseif are used, it is also an end.

For example

 　　if op == "+" then　　r = a + b　　elseif op == "-" then　　r = a - b　　elseif op == "*" then　　r = a*b　　elseif op == "/" then　　r = a/b　　else　　error("invalid operation")　　end

4. Try again

In addition to the for loop, Lua also supports multiple loops. Use the while... do and repeat... Until to rewrite the for program in this article.

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