Week 1, Day 3

Videos

1. Part 1: Review, Go → Javascript, Gravatar
2. Part 2: Stderr
3. Part 3: Gravatar Profiles cont'd, Go Tour, Word Count
4. Part 4: Word Count solution
5. Part 5: Count Clumps
6. Part 6: Count Clumps cont'd
7. Part 7: Pointers
8. Part 8: Pointers cont'd
9. Part 9: Swap, Rotate,
10. Part 10: Structs
11. Part 11: Structs cont'd
12. Part 12: Embedded Types, Interfaces
13. Part 13: Interfaces cont'd

Outline

1. Review

   • Create Javascript Cheat Sheet: is.gd/XaJQal.
   • Pair-program on problems

   Problems

   1. Create a program which reads user information (at least name and email) and creates a profile page in HTML. Also use or generate a profile image from gravatar.com.
   2. Implement WordCount. It should return a map of the counts of each “word” in a string. (You might find strings.Fields helpful.) WordCount("test test") → map[string]int{ "test": 2 }
   3. Implement a centeredAverage function that computes the average of a list of numbers, but removes the largest and smallest values. centeredAverage([]float64{1, 2, 3, 4, 100}) → 3
   4. Given a non-empty list, return true if there is a place to split the list so that the sum of the numbers on one side is equal to the sum of the numbers on the other side.
      canBalance([]int{1, 1, 1, 2, 1}) → true
canBalance([]int{2, 1, 1, 2, 1}) → false
canBalance([]int{10, 10}) → true
   5. Say that a "clump" in a list is a series of 2 or more adjacent elements of the same value. Return the number of clumps in the given list.
      countClumps([]int{1, 2, 2, 3, 4, 4}) → 2
countClumps([]int{1, 1, 2, 1, 1}) → 2
countClumps([]int{1, 1, 1, 1, 1}) → 1

2. Pointers

   • * and &
   • new
   • Scan

   Problems

   1. How do you get the memory address of a variable?
   2. How do you assign a value to a pointer?
   3. How do you create a new pointer?
   4. What is the value of x after running this program:

      func square(x *float64) {
      	*x = *x * *x
      }
      func main() {
      	x := 1.5
      	square(&x)
      }
      

   5. Write a program that can swap two integers ( x := 1; y := 2; swap(&x, &y) should give you x==2 and y==1).
   6. Generalize swap into a rotate function so that it works with any number of variables: rotate(&x, &y, &z), with x=1, y=2, y=3, yields x=2, y=3, z=1.
   7. Create a rotateRight function which does the same thing as rotate but in the other direction.

3. Structs and Interfaces

   • Structs
   • Initialization
   • Fields
   • Methods
   • Embedded Types

   Problems

   1. What's the difference between a method and a function?
   2. Why would you use an embedded anonymous field instead of a normal named field?
   3. Add a new method to the Shape interface called perimeter which calculates the perimeter of a shape. Implement the method for Circle and Rectangle.