CS320n

1
CS320n Elements of Visual Programming

• Assignment Help Session

2
What We Will Do Today

• Illustrate a few key points on the assignment and
  work on the assignment

3
The Assignment

• Simulate rolling two 6 sided dice
• Allow user to input number of times to roll
• numeric control
• this will be input to for loop count terminal
• inside for loop
• need to simulate rolling dice once
• need to count up how many times each result
  occurs
• can use an array to do this

4
Counting Number of Rolls

• One approach
• One way of counting number of times each value
  rolled
• store all results in an array
• go through array and count number of 2s, then
  number of 3s, then number of 4s
• A reasonable function would be how many elements
  of an array equal some value, but there is no
  LabVIEW function for this

5
Mapping

• Another approach
• A useful technique in programming
• instead of using an array to hold the results of
  the roll, use an array to count the number of
  times each roll occurs
• the index of the array is used to map to the
  result of a roll

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Sample Array
use result of roll as index into array
element indicates how many time that roll has
occurred. 1 two, 3 threes, 7 fours Assume the
next roll is a 4. How does array change?
7
Result is 4
Element at index 4 incremented by 1. Was 7, now
is 8.
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Using Mapping

• To use mapping auto indexing is not useful when
  rolling the dice and counting the results
• Need to use a shift register to pass whole array
  between iterations of the loop
• need to use the Index Array to get old value of
  element, increment it (add 1), and then use the
  Replace Array Subset function to update the
  element