Jenny Wang

How to C

2019-05-27T00:00:00+00:00

Popular things to include:

============================

#include

standard input and output

#include

strings

#include

exit() to exit out of code
rand() to create random numbers

#include

booleans
can use bool instead of _Bool

#include

getchar() recieves a string/char, can be put in variable
putchar(string) display the char
isalnum(char) and others (see below)
has an alphanumber been passed in? (a for 10, b for 11, etc)

#include

error handling

#include

calculate power of something

Define:

==========

#define MYNAME "Derek Banas"

all uppercase, a constant

#undef MYNAME

can redefine afterwards

Concepts and Strategies:

==========================

main looks like int main(){} and returns a 0 at the end
& is to get the pointer, * is for the value
- inverses

Print things on the screen from an array:

char *randomString = "Just some random stuff";
while (*randomString){ //null=>0=>ends while    
  putchar(*randomString++); //increment to chars
}
//OR
int i = 0;
while(randomString[i] != '\0'){
  putchar(randomString[i++]);
}

if you initialize a, but don’t give it a value before incrementing it, computer will take whatever was inside the place a is, increment it, and spit it out. “Random garbage”
arrays use row-major ordering, so it is array[y][x]

Data Types:

=============

char firstLetter = 'L';
int age = 38; //up to 32000
long int superBigNum = -3229384234; //bigger
float piValue = 3.14; //decimals (38 decimal #s)
double reallyBigPi = 3.1423842323i4uy23i4;

To describe variables:

=========================

unsigned = no negative digits

const = constant, unchanging

size_t = stores the amount of data in bytes

extern = variable was defined elsewhere, but use that var here, too

static = basically a “global” variable with a scope limited to where it was defined - functions: “you can’t call me out of my scope! >:D”

Relational:

=============

TRUE is anything other than 0

can an int be used in if(int) ?

FALSE is also 0

>, <, >=, <=, ==, !=, &&, ||

result comes out as 1 (true) and 0 (false)
!0 equals 1
!1 equals 0
To choose between two options:
```
  char* legalAge = (custAge > 21) ? "true" : "false";
```
- if true, return true. If false, return false
- can be put inside the %s part of printf()

Casting a value:

==================

to temporarily change the type

  //when the two numbers are ints:
  printf("numberEx / numberEx2 : %f", (float)numberEx/numberEx2);

Strings:

===========

If made by char ex[] = {‘C’, ‘a’, ‘\0’}, include ‘\0’ “naw” to end the string
or do char myName[] = “Something” (automagically puts \0)
see Functions

Pointers:

============

To pass data to other functions so they can use that local variable as well
can be in %p and %d (hexidecimal or not)
* to get what’s in the pointer
& to make it into a pointer
print the first index in an array:
```
printf("First: %d", *array);
```
print any other index because they are next to each other:
```
printf("Thrid: %d", *(array + 2));
```

Structs:

===========

more than one data type to describe something
need * for strings because of pointers

Example:

  struct dogs{

      const char *name;
      int height; 

  };

use typedef struct to make it so you don’t have to put struct everywhere else

“Make a new variable type”

Example:

      typedef struct dog{

          const char *name;
          int height; 

      } dog; //you can call it with dog
              //can put multiple names

To put info in:
```
  struct dog spike = {"Spike", 90};
```

To get the info in the struct:

  theName = theDog.name; //use the . OR
  theName = theDog->name; //OR
  theDog->name = theName;

To get addresses, use theDog.name for strings and
```
  &theDog.avgHeight for ints
```
When struct is passed to function, new struct is created, so need pointers

When doing * with structs, use ():

  (*theDog).weight = newWeight;

OR you can do
```
  *theDog->weight = newWeight;
```

struct dog cujo2 = cujo;

Can copy everything in a struct, including pointers

Union:

========

store 1 pieces of data that can be any type, but is not more than one type at a single time

Making one:

  typedef union{
        
      short individual;
      float pound;
      float ounce;

  } amount; //this union is named amount

  //set amount as 16, other values follow
  amount orangeAmt = {.ounce = 16};

  //changes the value of the whole union
  orangeAmt.individual = 4;

BE SURE TO USE THE CORRECT DATA TYPE
Can put them in structs
To initialize:
- Ex: orangeProduct is a type of struct named orangeProduct, theAmount is an union, so
```
  orangeProduct productOrdered = {"Chiquita",
      .theAmount.ounce = 16};
```

Linked List:

==============

Essentially make an infinitely long list with structs

Format of each struct:

  typedef struct product{

      const char *name;
      float price;

      struct product *next; //pointer to next struct

  } product;

if pProduct is the pointer of the given product, the next one in the line is pProduct->next
Add a new struct to the end:
```
  tomato.next = &potato;
```

add a new product, apple, between potato and lemon:

  potato.next = &apple, apple.next = &lemon, lemon.next = NULL

To go through all structs:
- go through all the items through next until you get NULL
To search for a struct:
- recieve a *productName
- set a varialbe to the first variable in the struct => name
- use strcmp() to compare
Deleting an item:
- Ex: Tomato, Potato, Lemon
- see what’s before potato from the time you were scanning for potato
  - potato’s next is now tomato’s next
- free() potato

Macros:

==========

A fragment of code that is given a name
name is read => whole code is pasted in
conventional = names are all UPPERCASE
Ex: #define MACRO_THINGIE 10 -> 10 is put in MACRO_THINGIE, replaces it

can make multiple lines

  #define MACRO_NUMBERS 10 \
                          2 \
                          3
  int x[] = {MACRO_NUMBERS};

makes: int x[] = {10,2,3};
weird error line numbers later on tho

Enumerated type

==================== For the times that you don’t need anything else other than what you put inside

Initialize:

==============

typedef enum{ INDIV, OUNCE, POUND } quantity;

To set the value: quantity quantityType = INDIV;

To do somethign:

if (quantityType == INDIV){
    blah blah
}

Line buffering:

=================

storing/scanning an amount of information before something is done to it

File I/O:

===========

Print out data from the file:

  char buffer[1000];
  while(fgets(buffer, 1000, pFile) != NULL){
      printf("%s", buffer);
  }
  //OR
  while(fscanf(pFile, "%s", buffer) == 1) 

returns # other than 1 if it doesn’t pass a string

Print directly to the file:
```
  fputs("Messing with strings", pFile);
```
- pFile is the way you are entering stuff
TO PRINT WHOLE THING, YOUR “CURSOR” HAS TO BE AT BEGINNING
To get number of bytes in whole file:
```
  fseek(pFile, 0, SEEK_END);
  ftell(pFile)
```
- because the “cursor” is at the end of the file
see Functions

Convert any base to any base:

===============================

For startingBase, endingBase, numberToConvert

numberToConvert % endingBase => put in array
Then numberToConvert = (numberToConvert - ) / endingBase
- and so on until you get an error with 1

Convert any base to base 10:

ex: binary 110 to base 10
- (1 * 2^2) + (1 * 2^1) + (0 * 2^0)

chars have values, too!

if(isalpha(number[i])){
    int charCode = ((int)tolower(number[i])) - 87;
    result += charCode * pow(baseFrom, toThePowerOf);
}

Bitwise operators:

====================

& And bitwise operator:

110 & 111 => 1 for every time they’re both 1
- 110 is result

| Or bitwise operator:

6 | 7 => if either is a 1, return a 1 => 111

^ exclusive or:

6 ^ 7
- 1 returned if one is a 1, other is 0
- 001 => 1 is returned

~ bitwise not:

~x
- if a bit in x == 0, that bit is now = 1
- if a bit in x == 1, that bit is now = 0
negative is the 2’s complement 000000010 => 2 111111101 => complement of 2 111111110 => add 1 to it
inverse sign = ~
- Ex: ~numberSix = -6
shift operators:
- shiftLeftTwo = numberSix << 2;
- x/pow(2, n) is the same as x>>n
bit masking
- if you want to see what is in some specific spots
- do 1 for parts you want to see, 0 for others
- do an AND bitwise operator

Functions:

============

printf("string, int %d, long int %ld, decimal with 2 decimal

places shown %.2f”, intValue, longIntValue, floatValue);
Displays to terminal
Conversion characters:
- %ld //long
- %d //int
- %.5f //prints to 5 decimal places
- %.15f //used for float and double
- %c //char
- %s //string
- %p //return hexidecimal addresses //also use & => printf(“%p”, &rand1)
\n = line, \t = tab, \\ = print, \" = print “

scanf("", &whereToStore, &otherPlace);

Ex: scanf(" %d/%d/%d", &month, &day, &year);
Store input from user, bulky
will overwrite values if there is a data overflow
needs the &
don’t use %d++ in the “” because it screws up
will return a 1 or 0 if compared with == to a number

fgets(storeHere, 30, stdin);

like scanf()
store the 30 bytes of information in storeHere through stdin
adds the \0 character
adds new line
accepts more than one string

fputs("string here", stdout);

string, output method
no new line

gets(name);

accepts one string and puts it in name
no new line. It ends with \0

puts("string here");

makes a new line after displaying the string

strcpy(myName, "Bob Joe"); //used to hold "Derek Banas"

assign a different value to the variable

strcomp()

returns negative # if first string is less than 2nd
returns positive # if more (second would come first if alphabetic)
returns 0 if equal

strcat(yourCity, yourState);

combine the two strings into yourCity

strlcpy(yourCity, "aksjdfl", sizeof(yourCity));

cuts off the end of the string so variable doesn’t overflow

strlen(name);

returns the length of the variable (number of slots)

theChar = getchar();

Takes in chars until enter is pressed

putchar(theChar);

print the char on the screen

strrchr(randomString, '\n');

returns last occurance of \n in randomString

strchr(randomString, 'a');

returns first occurance of a in randomString

tolower(char)

makes the letter lower cased
Ex: theString[i] = tolower(theString[i]);

toupper(char)

makes the letter upper cased

isalnum(char)

is it consisting of all numbers?

isalpha(char)

alphabetic character

isblank(char)

space

isdigit(char)

digit

isgraph(char)

anything but space

isupper(char)

upper cased

islower(char)

lower cased

ispunct(char)

punctuation

isspace(char)

any space

strcmp(string, string)

comparing two string sto see if they match
returns 0 if they’re the same
returns (+) if first string more (further in alpha order)
returns (-) if first string is less

exit()

Close program. Don’t run anything else.
can be (0),(1),(2),(3),(4), etc for personal reference

rand()

Create random number
To get numbers 1-50: rand() % 50 + 1

break;

exit out of an infinite loop (is like exit())
used in switch

continue;

go back to the beginning of the braces

Ex:

  for(blah){ 
      //do something, start here again!
      if (variable == 1){ continue; }
      //don't do this stuff this time
  } 

switch(whatToDo){
        
    case(1) : printf("Print the time");
        break;

    default : printf("Bye");
        exit(0);
        break;

    }

if whatToDo == 1 (in case(1)), do that
go on to other cases
default is done if nothing else works
if there isn’t a break, it will execute all the other statements after the one it entered in on range is 4…6 instead of 4 or something

sizeof(variableName);

returns the number of bytes in there

pRandomNumbers = malloc(amountOfBytesToStore);

if fails, stores a NULL
Good usage to store a specific number of ints:
- malloc(amtOfNumbersToStore * sizeof(int))

free(pRandomNumbers);

free memory for pRandomNumbers to prevent crashing
used for large scale programs that don’t end in a while

pFile* = fopen("fileName.txt", "w");

will make the file if it doesn’t exist
binary files (.bin) use things like rb+
- “w” - stuff already inside will be deleted/replaced
- “a” - append or add new info
- “r” - read from the file
- “a+” - start at end of file if it exists and reads and writes
- “r+” - open at beginning for reading and writing, no delete, no make new file
- “w+” - delete original (or make new one if no exist), read and write
if file wasn’t opened, returns a 1

fprintf(pFile, "%d", randomNumber)

print it to the file like printf()
file to print to, what to print

fclose(pFile)

close the file, if not closed, returns 0

if went well, returns 1

  if(fclose(pFile)) != 0){
      printf("Success writing to text");
  }

fseek(pFile, 12, SEEK_SET);

can use (-) numbers in fseek()
12- move 12 characters => “moving the cursor”
Seek things:
- SEEK_SET - Start from beginning of file
- SEEK_CUR - Move from current position in file
- SEEK_END - Based off of end of file
in binary mode, need to * number chars to move by the size of each thingie => move 12 => 12 * sizeof(int)

ftell(pFilfe)

returns the number of bytes the cursor is from the beginning of the file

perror("Error Occured");

prints that and the standard error message

printf("Error Code %d\n", errno);

prints error code

fwrite(name, sizeof(name[0]), sizeof(name)/sizeof(name[0]), pFile);

Write binary data to file
pointer by default
variable, size of each element, number of elements, where to print

fread(buffer, 1, fileSize, pFile);

dataInFile = fread(blah blah);
information goes to buffer, bytes taken from each element,
- number of elements, read from this place

rewind(pFile);

go to beginning of file

pow(base, toThePowerOf);

mutiply base and itself toThePowerOf times

How to Java (APCS level)

2019-05-27T00:00:00+00:00

Accessible methods in the Java Quick Reference

===============================================

Object

boolean equals(Object other)
String toString()

Integer

Integer(int value)
int intValue()
- returns value in int
Integer.MIN_VALUE
- smallest value that can be stored in an int
Integer.MAX_VALUE
- largest value that can be stored in an int

Double

Double(double value)
double doubleValue()

String

int length()
String substring(int from, int to)
String substring(int from)
int indexOf(String str)
int compareTo(String other)
- returns
  - 0 if equivalent
  - some number > 0 if earlier in alphabet
  - some number < 0 if later in alphabet

Math

abs(int/double x)
pow(double base, double exponent)
sqrt(double x)
double random()
- double in the range [0,1)

List

int size()
boolean add(E obj)
- returns true after adding it ._.
void add(int index, E obj)
E get(int index)
- if it’s a number, returns Integer/smth else
  - (not int/double, but Integer/Double)
E set(int index, E obj)
E remove(int index)
- changes indices of next elements. BEWARE IN LOOPS

TERMS

========

API = Application Programming Interface
- methods, routines, etc used to program
nested/inner class
```
  class foo {
      class bar {...}
  }
```
- ^^ bar is nested class
- bar sees everything from foo, but isn’t a foo
- ex: String is a nested class of Object
child class
- class bar extends foo {...}
- ^^bar is child class
- bar sees everything from foo, and is a foo

KEYWORDS

===========

implements

for interfaces (methods not defined)
provide definitions for APIs

extends

for Classes (methods defined)
parent-child relationship

static

modifies/takes stuff from the class
nonstatic (aka not putting static there) modifies the instance

Integer/Double

can == null => can’t assign null to an int
- otherwise, it’s the same as int/double in Java 5+

List

from index 0
see methods
to initialize
- List a = Arrays.asList(ele1, ele2, ...);
is immutable (cannot be modified)
is an interface

ArrayList

extends AbstractList that extends List
from index 0
to initialize
- ArrayList a = new ArrayList(Arrays.asList(ele1, ...);
is a Class

CONTROL STATEMENTS

=====================

enhanced for loop (“for-each”)

  String[] array = {...};
  for (String element : array) {
      //do something for all elements in array
  }
  the same as:
      for (int i=0; i
    



SORTS
========


  insertion sort
  selection sort
  bubble sort
  mergesort
  heapsort
  quick sort


==================================================

Java unrelated to APCS


  concurrency
    
      processes happen at the same time
      use threads
    
  
  immutable
    
      that instance cannot be changed after it is made
      uses the keyword final
    
  
  \unnnn (escape sequence like \n)
    
      line break LOL
    
  
  assert 
    
      check for bugs in the code
      if expression after it is false, it stops the program
      ex: assert varIsTrue == false



How to MATLAB
2019-05-27T00:00:00+00:00
Numerical Data Structures
==========================

cell

vector = row/column

matrix = group of vectors

  is a rectangle


array = 3d matrix

Initialize matrix
    
    matrix = [1 1;2 2]
   

  ; = new row
   = next column


Specify # of cells

  matrix = zeros(numRows, numColumns)
  matrix = ones(numRows, numColumns)
    
      or ones([numRows numColumns])
    
  


Call data from all numRows rows or numColumns columns

  replace with :
  ex: matrix(:,4)


vector = [1:100]

  fills vector with numbers 1 to 100


vector(row, col) = 10

  change cell value


vector(row, col)

  get number and print it out


sum(vector)

  sums all numbers in vector


prod(vector)

  multiply everything in vector


Math between two vectors/matrices

  use +, -, *, /


Math between correlating cells in vectors/matrices

  use +, -, .*, ./


vector = vector';

  make the row vector into a column vector


matrix(:)

  take all cells in the matrix


=================================================

Other Data Structures
=======================

Strings are in single quotes ‘’

num2string(var);

  change data type


string2num(var);

  change data type


=====================================

Miscellaneous Syntax
=======================

NaN = null

% = comment

... at the end of the line when you want to press enter

  ex:
      var1 *...
  var2
    
  
  put semicolons in scripts
    
      won’t print onto command window
    
  


lowerLimit:upperLimit

  vector with all numbers from lowerLimit to upperLimit


~ = not

|| = or

&& = and

for loops
    
    for i = start:end
        %do something
    end
   

if statemtents
    
    if %condition
        %action
    else
        %action
    end
   

===============================

Random Functions
==================

vector = xlsread('fileName.extension')

  Read Exel file


image = imread('imagename');

  read image


linspace(start, end, n_points);

  returns equally spaced points
  includes starting and end points


[x,y] = meshgrid(xVector, yVector)

  returns all possible coordinates of pts
  use with linspace


size(vector, )

  returns numRows, numColumns
  don’t specify row or column if want both


imageB = imresize(imageA, scale);

imageB = imresize(imageA, [numRows, numCols]);

  imageB has numRows rows and numCols cols
  or put NaN as one of them to preserve aspect ratio


imshow(image);

  make a window with the image on it


sind(theta)

  sin


cosd(theta)

  cos


repmat(vector, numTimes)

  repeat the vector numTimes horizontally and vertically


repmat(vector, numRows, numColumns)

  have that many total rows/cols


shuffle(vector)

  change up the order of all cells, use with repmat


shuffle(vector, dimension)

  dimension: 1 = Rows change, 2 = Columns change, 3 = next dimension changes, etc


vertcat(vector, vector2, vector3, ...)

  stacks vectors ontop of each other


horzcat(vector, vector2, vector3, ...)

  stacks vectors side to side


RandStream.setGlobalStream(RandStream('mt19937ar', 'seed', sum(100*clock)));

  put it everywhere just in case you want a random number (for real randomness)


randperm(upperLimit, numCells);

  can’t get the same number twice


randperm(upperLimit)

  numbers 1~upperLimit are reordered


randi(upperLimit);

  get one random number


randi(upperLimit, numRows, numCols);

  random numbers in matrix numRows x numCols


randi([lowerLimit, upperLimit]);

  number from lowerLimit to upperLimit


randsample(upperLimit, numCells);

  numCells number of random numbers


randsample([1 2 3], 2)

  numCells number of rand numbers from the vector


any(vector)

  returns true if any of cells is nonzero


floor(num)

  returns num rounded down to whole number


ismember(element, vector)

  returns true if element is found inside the vector


WaitSecs(seconds);

  how long to wait


GetSecs()

  get seconds from start of program
  use to make sure the time intervals are right


[keyIsDown, secs, keyCode] = KbCheck()

  if have different keyboards, put 1/2/3/4/5 in parenthesis for specific keyboard
  keyIsDown = any button down (1 or 0 => true or false)
  secs = time from GetSecs()
  keyCode = key that is down
    
      ex: strcmp(‘s’, KeyName(keyCode)), see if it is ‘s’
    
  


[x,y,clicks] = GetMouse()

  x, y = mouse position coordinates
  if clicks = [0,0,0] => no click, [1, 0, 0] = left click
  test with any(clicks)


GetClicks()

  get number of mouse clicks


strcmp(string1, string2)

  returns true if identical, false if not


string = strcat(string1, string2)

  combine string1 and string2


KeyName('UnifyKeyNames')

  make codes from key presses the same from macs/windows/etc


save(fileName, 'variable')

  ex: save('result', 'p', 'q');
  save some variables in a file (.mat)


string = upper(string)

  all letters uppercase


isdir(directoryString)

  true if there already is a directory with that name, false if no
  example of directoryString is from pwd()


mkdir(directoryString)

  create a folder with directory directoryString


sortrows(matrix, colNum)

  make numbers in the colNum-th column be in ascending order


resizem(input, scale)

resizem(input, [numRows, numCols])

  expand and contract matrix


====================================================

Command Line Commands
=======================

COMMANDS CAN BE PUT INTO SCRIPTS

pwd

  print your directory
  usage examples:
      rootDir = pwd();
  resultsDir = [rootDir '/results/']
  if ~isdir(resultsDir) %if don't have this directory already
      mkdir(resultsDir) %make the directory/folder
  end
    
  


cd(folderName)

  change directory
  go one level up => cd ..


ls

  list of files in the folder


clear all

  clears variables from other experiments


clc

  clear command window


===========================================

Keyboard Shortcuts
====================

ctrl+c then s then c then a then enter

  bring back window (if it crashes)
  might need to alt+tab (switch windows) before doing above


=================================================================

Psychtoolbox
===============

A library for psychology experiments

Screen has many settings

  access w/ Screen('something', , , );
  Screen('CloseAll');
    
      closes all screens
    
  
  Screen('Preference', 'SkipSyncTests', 1);
    
      yes to skipping sync tests
    
  


[window, rect] = Screen('OpenWindow', 0, [], [500 500 700 700]); 

  open the window
    
      0 = open on this monitor
      1 = open on other monitor
    
  
  2nd matrix = where the screen will be
  window = pointer
  rect = (startX, startY, endX, endY)
    
      corner coordinates;
    
  
  Screen puts data into window/rect


x = Screen('MakeTexture', window, uint8(image));

  uint8 because colors in image can’t be > 255


Screen('DrawTextures', window, x);

  draw the texture. x is from function above


Screen('DrawTextures', window, tid(rand_oranges(i,:)), [], xy_rect, orientation);

  xy_rect = corners of each picture
  orientation = degrees of rotation=========================================================================


A = Screen('Flip', window);

  display onto monitor
  usually don’t need A


Screen('Flip', window, A + seconds);

  show a blank screen (if nothing is made with window) second seconds later
  more accurate than WaitSecs()


KbWait(); 

  
    wait for keyboard input before going on
  
  
    how to get rid of background of image
    
      add transparent mask ontop
      mask must be same size as image
    
  



How to Javascript
2019-05-24T00:00:00+00:00
HTML STUFF
============







  onload- does function()




  make a js script