Lua expression and control structure learning note _ node. js

This article mainly introduces Lua expressions and control structure learning notes. This article describes Arithmetic Operators, Relational operators, logical operators, local variables and scopes, and control structures, for more information, see Arithmetic Operators

Lua's arithmetic operators include:

"+" (Addition ):

The Code is as follows:

Print (1 + 2)

"-" (Subtraction ):

The Code is as follows:

Print (2-1)

"*" (Multiplication ):

The Code is as follows:

Print (1*2)

"/" (Division ):

The Code is as follows:

Print (1/2)

"^" (INDEX ):

The Code is as follows:

Print (27 ^ (-1/3 ))

"%" (Modulo ):

The Code is as follows:

Print (5% 3)

Relational operators

Lua provides the following Relational operators:

The Code is as follows:

<> <= >== ~ =

The operation results returned by the preceding operators are true or false. Strings and numbers cannot be compared.

Logical operators

Logical operators include and, or, not

The Code is as follows:

Print (1 and 2)
Print (nil and 1)
Print (false and 2)
Print (1 or 2)
Print (false or 5)

Logical operators treat false and nil as false, while others are true.

Local variables and scopes

Lua uses the local statement to create local variables. The scope of local variables is limited to the block that declares them.

The Code is as follows:

Local a, B = 1, 10
If a <B then
Print ()
Local
Print ()
End
Print (a, B)

You can use local to save global variables to accelerate access to global variables in the current scope. For the acceleration effect, compare the execution time of the following computation of the Fibonacci series (Fibonacci:

The Code is as follows:

Function fibonacci (n)
If n <2 then
Return n
End
Return maid (n-2) + maid (n-1)
End
Io. write (maid (50), "\ n ")

Use local variable

The Code is as follows:

Local function fibonacci (n)
If n <2 then
Return n
End
Return maid (n-2) + maid (n-1)
End
Io. write (maid (50), "\ n ")

Control Structure

If then elseif else end

The Code is as follows:

If num = 1 then
Print (1)
Elseif num = 2 then
Print (2)
Else
Print ("other ")
End

Lua does not support switch statements.

While

First, judge the while condition. If the condition is true, execute the loop body. Otherwise, the process ends.

The Code is as follows:

Local I = 1
While a [I] do
Print (a [I])
I = I + 1
End

Repeat-

Execute a loop body first, and then judge the condition. If the condition is true, exit the loop body; otherwise, continue to execute the loop body. Similar to do-while statements in other languages, the loop body must be executed at least once.

The Code is as follows:

Local a = 1
Repeat
A = a + 1
B =
Print (B)
Until B <10

For Loop

The for loop statement can be in the numeric type for (numeric for) or generic for (generic)

Numeric for syntax:

The Code is as follows:

For start, end, step do
Doing something
End

Start indicates the start value, end indicates the end value, and step indicates the step size (optional, 1 by default)

The Code is as follows:

For a = 10, 0,-2 do
Print ()
End

A generic for loop uses an iterator function to traverse all values:

The Code is as follows:

Tab = {key1 = "val1", key2 = "val2", "val3 "}
For k, v in pairs (tab) do
If k = "key2" then
Break
End
Print (k .. "-" .. v)
End

The break and return statements are used to jump out of the currently executed block.