Research Topics in Computational Science

Agenda

• Survey Overview

Notes on the Survey:

• End on Time– I will try to end 10 min early for work & qus

• This isn’t too slow– Nobody said slow, but some said fast

• Upload Class Code– More time on my code (I will slow down)

• Go Quicker: with questions• Go Slower: with in class coding

Today’s Agenda

• Code with notes– practice for homework set

• Download the PPT to follow along with while coding

Indexing And Arrays

• In C we start counting at 0• The “1st” value is actually the “0th” value in C

Array Indeciesdouble x = {0.0, 3.14, …, 1.1, 2.7}

0.0

• x[0]

3.14

• x[1]

…

1.1

• x[n-2]

2.7

• x[n-1]

The computer needs to set aside memory, then the values can be placed in memory.

For an array of n elements we start at element 0 and access up to element n-1.

Arrays

• An array is a data object of a fixed size to hold many variables of the same type

• int[] a, b, c; // Will create 3 integer arrays• This doesn’t allocate memory for the array• a = new int[10];• Allocates memory for 10 ints in array a

• int[] a = {0,1}; //declare, allocate, assign values

Lists

• List<int> – Creates an int list

• List<double>– Creates a double list

• List<string>– creates a list of strings

• List<someType>– creates a list of the type

specified between <>

• We can create lists of any object

• We can have a list of buttons or images

List Functions

• x = myList[3];– gets the value at index 3 from the list

• myList.Add(3.14);– Adds the value 3.14 to the list

• myList.Remove(3.14);– removes first occurance of 3.14 from the list

• myList.RemoveAt(3);– removes the item myList[3]

c++, c--, ++c, --c

• Only used for “int”• c++ and ++c will add 1 to the

variable c– c++ will use c, THEN add 1– ++c will add 1 to c, then use it

• c-- and --c will subtract 1 from the variable c– c-- will use c, then subtract 1– --c will subtract 1, then use c

Example:c = 0;mbox(c++);//displays 0mbox(c);// displays 1mbox(++c);//displays 2

For Loop

• This will loop a specified number of times, AND increment a variable (usually i, j, or k)

• There is a standard loop that is used MOST of the time

• You can change as needed

For Code

for (int i=0; i<5; i++) { mbox(“Hello” + name[i]);}

• This will say hello to the first five names in the array “name”

• Start at i=0• Continue while i<5• At the end of every loop

do the operation i++

For Each Loop

• This will loop through each element of an array or list

• This can be very useful when we don’t know how many things are in our list/array

ForEach Code

int cider = 0;foreach(int age in ages){if(age<20) cider++;/* count the number of cider drinkers */}

• We have to declare the type, here it is an int

• We have to give a temp name, age is a clear name for this

• We have to give the name of our array/list

While Loop

• While loops can run forever!– Becareful of infinite loops

• These will run while a statement is true

While Loop Example

bool myval = 1;while( myVal < 100 ) { myVal = myVal * 2;}

• This will find the smallest power of 2 greater than 100.

• After each loop it checks the while

Do While Loop (aka do loop)

• This loop will ALWAYS execute one time• At the end of the loop it checks to see if it

should run again

Do While Loop

myVal = 200;do { myVal *= 2;} while (myVal < 100);

• This does the same thing as the last loop.

• Even though 200 will give a false value for “while” it will still do the loop one time

Switch Control

• Select based on matching input

• This is good when you have a lot of cases to be tested for.

Switch Code

switch( word ) { case “boy”: // do this break; case “girl”: // do this break; default: // do this break;}

• If the variable word is the same as “boy” it will do the first statement

• it will try every CASE until it finds one that matches or the end.

• Every case must have a break.