C# 05 Study Notes Compound and Iteration statements

5.Compound and Iteration statements

5.1. Compound Assignment Operator

📌What is it?

int num = 13;
num = num + 28;  //this is not
num += 28;  //this is compound

📌Recommend

Don't😶	Yes!😄
num = num + variable;	num += variable;
num = num - variable;	num -= variable;
num = num * variable;	num *= variable;
num = num / variable;	num /= variable;
num = num % variable;	num %= variable;
num += 1;	num++;

5.2. while loop

📌while loop in abstract

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initialization
while(Boolean expression)
{
    statement
    update sentinel variable
}

📌sentinel variable哨兵变量

The variable to end the while loop.

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int i = 0;  //sentinel variable
while(i < 10)
{
    Console.WriteLine(i);
    i++;
}

5.3. for loop

📌for loop in abstract

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for(initialization; Boolean expression; update sentinel variable)
{
    statement
}

📌for loop in real

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for(int i = 0; i < 10; i++)
{
    Console.WriteLine(i);
}

📌Multiple variable for loop⭐️

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for (int i = 0, j=10; i < j; i++, j--)
{
    Console.WriteLine($"i val:{i}, j val:{j}");
}

Output:

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i val:0, j val:10
i val:1, j val:9
i val:2, j val:8
i val:3, j val:7
i val:4, j val:6

📌for loop can do more!⭐️⭐️⭐️

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for(string line = reader.ReadLine(); line!=null; line=reader.ReadLine())
{
    source.Text += line + "\n";
}

📌Variable in for loop is local variable

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for (int i = 0; i < 5; i++)
{
    Console.WriteLine($"Say {i}.");
}
for (int i = 20; i > 15; i--)
{
    Console.WriteLine($"Yell {i}!");
}

Output:

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Say 0.
Say 1.
Say 2.
Say 3.
Say 4.
Yell 20!
Yell 19!
Yell 18!
Yell 17!
Yell 16!

5.4. do statement

📌do in abstract

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do
{
    statement
}while(Boolean expression)

📌do in real

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int i = 0;
do
{
    Console.WriteLine(i);
    i++;
} while (i < 10);  //don't forget the ;  here

📌difference between do-while and while

In short, do-while has to do it at least once before iterating!

📌break and continue

Same with it in Python,

• break - it jumps out the for/while loop directly
• continue - it goes to the next iteration of for/while loop