Loops 10 10 2011 Opening Discussion Minute essay comments Midterm covers topics through today IcP selection is weighted by how many you have left to do while Loop The simplest loop is the while loop while condition statement The condition is evaluated first If it is true the statement possibly a block executes This repeats until the condition is false do while Loop The partner to the while loop is the do while loop do statement while condition This loop is post check instead of the pre check of the normal while loop Always happens once The while loop might never happen The for Loop The most commonly used loop in most languages is the for loop The Scala version is a bit different from most Often used for counting In general it is a for each loop that goes through a collection for i 1 to 10 for e coll Variable takes on value of each element in the collection Range Type Range types provide an easy way to make collections for counting to and until operate on numeric types to produce ranges 1 to 10 0 until 10 Use by to change the stepping in a range 1 to 100 by 2 10 to 1 by 1 a to z by 3 yield The for loop can be used as an expression if you put yield between the end of the for and the expression after it for e coll yield expr What you get back will be a collection that is generally of the same type as what you iterated over if Guards You can put conditions in the for that will cause some values to be skipped for n nums if n 2 0 Multiple Generators You can also put multiple generators in a for loop for i 1 to 10 j i to 10 You can combine as many generators and guards as you want You can also declare variables in the middle of the for The thing you assign into is like a val so it can be a pattern We have only seen this with tuples so far Multidimensional Arrays You can have collections of collections A common example would be something like Array Array Double to represent a matrix Both fill and tabulate can be used to make these val ident Array tabulate 3 3 i j if i j 1 0 else 0 0 Minute Essay Any questions Midterm is on Wednesday The review session will be 5 00 6 00pm Monday here and 7 008 00 Tuesday on Google
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