C wars: Chapter 4: A new loop
Chapter four: A new loop
Today, I'll talk about one of the most important structures in programming:
This series is taking a 24 hour break. Yes, no post on Wednesday.
The loop
You know what a loop is in real life, right?
Good.
A loop in programming does the same thing, except it does it based on a boolean value.
Loop #1: While.
This loop has no magic. Just does the code inside {}
while bool
is true:
while (bool) { }
For example:
while (true) { printf("Linux is better\n"); }
Will output:
Linux is better Linux is better Linux is better Linux is better Linux is better Linux is better Linux is better Linux is better Linux is better Linux is better ...
Let me introduce you to a new function, getchar()
.
This reads a char from STDIN and returns it.
So let's make a program that reads input:
#include <stdio.h> int main() { char c; while ((c = getchar()) != EOF) { printchar(c); } }
This introduces a few new concepts.
When you put an assignment in ()
, you can use it to compare.
So
char c = 65; while (c != EOF) { printchar(c); c = getchar() }
is equal to
char c; while ((c = getchar()) != EOF) { printchar(c); }
Loop #2: For loops
These are a little more complex.
They have the syntax
for (assignment; bool; change){}
The assignment is usually int i = 0
.
This sets i
to 0;
The bool is a boolean, usually dealing with i
.
For example: i < 10
.
And change is how to change the variable.
For example: i++
.
Now is a ripe time to introduce to two new operators:
++
This changes tha double
/int
by one.
There are two forms:
++i
i++
What's the difference?
Well, i++ adds one to i, but returns i.
For example:
int i = 1 printf(i++); printf(i)
Will say:
1 2
While ++i will say:
2 2
Now, back to the for loop:
To print all the numbers between 1-100, you would use:
for (int i = 0; i < 100; i++) // Needs 0 printf(i);
Loop #3: Do while.
This loop is a bit overlooked.
To know why this loop exisits, we have to look a little close at the while loop.
If you have this code:
int i = 0; while (i != 0) { super_important(); }
Will it run. No. (We can't tell if it will halt, though.)
However, if you use a d-w (do-while), it will run.
The D-W syntax is:
do { } while (bool)
Again, bool is a boolean condition.
So you can complete your homework, I need to teach you one more thing:
The %
operator.
This computes the remainder between two numbers.
It's commonly used to check if a number is even.
if (num % 2 == 0)
Homework
Now, make a program that computes the Collatz conjucture
The Collatx conjucture states:
If a number is even, divide it by two.
If not, triple it and add one.
If you do this enough, it will become one.
Impliment this in C.
Please progmpt the user for input and print out the number after each cycle:
8 42 1
or
17 52 26 13 40 20 10 5 16 8 4 2 1
So long!
Part One: The Segfault menace
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Also C bad anyway :D
Lol yes @Jakman
Pointers are incredibly easy and fun. Manual GC is a pain. @Jakman
@Jakman Think about iSegmentation fault (core dumped)
@CodeLongAndPros PTSD Intensifies
Pointers are fun to work with. Especially in OS development, which I do most often. Way better than manually keeping track of memory locations in x86 Assembly. @Jakman
@CodeLongAndPros I legit had some flashbacks of Segmentation fault errors. Good thing I use Rust now.
Ew Rust. @Jakman
In the plain of unemployment. @Jakman
It also lands you in your mom’s basement at 30. @Jakman
You get the point. @Jakman
Manjaro bad Ubuntu is better tbh -_-
Hey @CodeLongAndPros can you do me a favor?
@HahaYes Perhaps. I make no promises.
@CodeLongAndPros umm can you report the next comment to rick roll the repl staff?
@CodeLongAndPros gotta rickroll amasad and patrick
@CodeLongAndPros You spelled chapter wrong.
@lightningrock Day 6? In two days?
@lightningrock No, wait. three. Taking a break between D4 and 5
@lightningrock Sorry, have to brush up on pointers.
no it's fine @CodeLongAndPros
@lightningrock wait did you mean me? This is @CodeLongAndPros C tutorial not C++ tutorial. And yes, day 6 is coming out today.
oh wait i get them mixed up. tbh, i'm not sure which one i meant @HahaYes
@lightningrock hmmm I think you mean me. Now unvote this and vote yes for mine.
maybe @HahaYes
@lightningrock jk just upvote mine so I can beat everyone. If I'm Pewdiepie, then he is bad T-Series. But I'm T series?
@HahaYes Now that is unfair.
@CodeLongAndPros what did you make that yourself
@HahaYes Well yes. Try to find the link to it
I upvoted both none.
@HahaYes @CodeLongAndPros
hmmm gotta find a way to make this popular