MarcElrick

Folds

Folds allow us to use perform iterative operations in Haskell without the need to use loops. We can fold from the left (foldl) or fold from the right (foldr).

foldl

A left fold is fairly simple to comprehend. A left fold takes the form

foldl func acc lst

where:

MarcElrick

# Set keyboard layout for keychron board

kc(){
    for id in $(xinput list | grep K3 | grep keyboard | cut -d '=' -f 2 | cut -f 1); do setxkbmap -device $id -layout us;done;exit;
}

MarcElrick

Data Types and Sizes

There are only a few basic types in C. These are:

Data Type	Size
int	integers of machine specific size (usually 16 or 32)
double	double floating point values
float	single floating point values
char	single byte ASCII characters

MarcElrick

Format Specifiers

Return Type	Format Specifier
char	%c
int	%d
float	%f
long	%l
double	%lf
long double	%Lf

MarcElrick

Memory Allocation

The following memory allocation functions are all part of <stdlib.h>:

function	return type	declaration
malloc	void *	malloc(size_t size)
calloc	void *	calloc(size_t nitems, size_t size)
realloc	void *	realloc(void *ptr,size_t size)
free	void	free(void *ptr)

MarcElrick

Pointers, Arrays and Structs

Pointers

The address of a variable in C can be obtained using the & operator and so to find the memory address of a variable var we would use &var.

Similarly, we can use * to 'follow' a pointer through to the variable at said address so if p_var points to var then then we can obtain the value of var using *p_var.

// Assign the value 5 to var.
int var = 5;

MarcElrick

Android Rooms

There are 3 main components within rooms:

• Database
• Entity
• DAO - Data Access Objects

Database

The database is an abstract class with the @Database annotation which will extend RoomDatabase. It will include the list of entities associated with the database within the annotation.

MarcElrick

Android Notes Part 1 - Android Core

Toasts

A toast is a short message that appears on the screen for a short time period.

// A basic toast can be created as follows:
val text = "Hello toast!"
val duration = Toast.LENGTH_SHORT

val toast = Toast.makeText(applicationContext, text, duration)