Programming/C++/Syntax

Note: Common File Extensions: .cpp .h

Compiling C++

To run any C++ code, it must first be compiled.

To do this, in terminal, cd to the desired directory and run g++ <path_to_file> -o <name_of_file_to_create>.

This will generate a new executable file, based on the compiled code.
Run this file via ./<name_of_created_file>.

Types of Errors

• Compile Time Errors - Errors that happen during file compile.
  • Syntax Errors - Errors that happen from incorrect typed syntax for the given language.
  • Type Errors - Errors that happen due to mismatch of declared type and attempted type usage.
• Link Time Errors - Errors that happen when trying to combine compiled files into a single executable program.
  • Ex: Using a function that was never defined, or Main() instead of {{ ic |main()}.
• Run Time Errors - Errors that happen during program execution.
  • Ex: Divide-by-zero errors, or attempting to open a file mid-runtime and said file doesn't exist.
• Logic Errors - Soft errors that don't cause an actual crash. But can cause a program soft-lock, or general unintended behavior.

Comments

Inline Comments

// This is an inline comment.

Block Comments

/**
 *This is a block comment.
 *Comment line 2.
 *Another block comment line.
 */

Basic Input and Output

Basic Output

A very basic output example is:

#include <iostream>

std::cout << "Hello World!\n";

We can also chain together strings this way:

#include <iostream>

std::cout << "Hello " << "World!" << "\n";

If we exclude the \n, then output will remain on a single line:

#include <iostream>

std::cout << "Hello ";
std::cout << "World!";
std::cout << "\n";

The above code snippets are all functionally equivalent.

Basic Input

Similar to basic output:

#include <iostream>

std::cin >> <variable_here>

For example:

#include <iostream>

// This will read in a string as a variable, then immediately display it.
string my_string;
std::cin >> my_string;
std::cout << my_string << "\n";

Variables

Variables are strongly typed in C++. That means you must declare the type as well as the name.

Variable Definition

bool a_bool = true;
bool b_bool = false;
string my_var_1 = "This is ";
string my_var_2 = "a string.";

Variable Usage

#include <iostream>

std::cout << "Printing variable values.\n";
std::cout << a_bool << "\n";
std::cout << b_bool << "\n";
std::cout << my_var_1 << my_var_2 << "\n";

Booleans

C++ uses the following bools"

bool true_bool = true;
bool false_bool = false;

Null Values

C++ uses the standard null.

int null_value = null;

If Statements

Basic If

if (x == y) {
    # Logic if true.
}

Full If

if (x == y) {
    # Logic if true.
} else if (! x && (y || z)) {
    # Logic for "else if" true.
} else {
    # Logic for false.
}

Switch/Case Statements

switch (<conditional_statement) {

    case <result_1>:
        # Logic if matches <result_1>.
        break;
    case <result_2>:
        # Logic if matches <result_2>.
        break;

    ...

    default:
        # Default/fallback if no matched results.
        break;
}

Note that the break statements are optional, but recommended. Removing a break statement will make the code execute into the next result section, instead of exiting the switch block.

Loops

For Loop

for (<counter_var> = <start_index>; <end_condition>; <counter_var_modifier>) {
    # Loop logic here.
}

Ex:

for (int index = 0; index < 10; index++ {
    # Loop logic here.
}

While Loop

while (<condition>) {
    # Loop logic here.
}

Functions

<return_type> <function_name>(<arg1>, <arg2>, ..., <argn>) {
    # Function logic here.
    return <return_value>;
}

Ex:

# This is a function that returns nothing.
void my_function() {
    # Function logic here.
}

# This is a function that returns an int.
int my_function() {
    # Function logic here.

    ...

    int my_return_int = 5;

    ... 

    return my_return_int;
}

# This is a function that returns nothing, but takes three parameters.
void my_function(int my_int, std::string my_string, bool some_other_arg) {
    # Function logic here.
}