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Welcome back. We can also use the accumulator pattern to accumulate strings.

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In this case, you start with an empty string and keep appending to it.

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But when you append, you'll have to reassign to

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the accumulator variable because you can't actually change the original string.

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So here's an example,

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a Michigan winter example where you've got someone who's got chattery teeth,

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because it's so cold outside,

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all of their letters are coming out double.

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So they're going to say a word like

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"Hello" and because their teeth are chattering it comes

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out as "Helloo". So here's how we do that.

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We're going to start by asking the user to type in a value that's on line one,

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they enter some text and that gets assigned to the variable s. Let's suppose that,

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let's make it easier for us, they say "cat",

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the accumulator variable is going to have our results so far,

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teeth chattering version of that string that we've accumulated so far.

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Initially, there's nothing but it's going to accumulate things,

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and then we start iterating one letter at a time,

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the variable c is going to be bound to the letter "c",

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and then we are ready to execute the accumulation part line four for the first time.

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So it's going to take our current value of ac which is an empty string,

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it's going to add the current value of c which is the letter "c",

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and then it's going to give us a dash and the letter "c" again and another dash,

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which yields a string "c-c-",

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and that becomes the new value for ac.

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The old string is still there but we don't worry about it anymore

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because ac has been reassigned to this new string cat cat.

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We're now ready to go onto the second iteration,

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where we get to line four for the second time c is now bound to the letter variable "c",

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c for character is now down to the letter "a",

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the second letter in our string,

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and we're now going to make a,

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let me write it over here,

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we're going to make a string that has the old value of

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ac and then we append the letter a and a dash,

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and a again and another dash,

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and that becomes our new value.

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Similarly for "t" we're going to extend

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this each time that

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we do all this concatenation,

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we have to re-assign to a,

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because we're not actually changing the own,

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we have to reassign to the variable ac I should have said

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and we have to do that because ac has not been changed.

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So we've made a new string and we re-assign it to ac.

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So, in summary, to accumulate a string,

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you start with an empty string, on each iteration,

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you re-assign the accumulator variable with a concatenation of

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its old value and some new stuff.

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At the end, you've accumulated something like" c-c-a-a-t-t.

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So let's run it, I enter cat, I get c-c-a-a-t-t,

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Michigan frozen winter speaking picking cat or if I run it and ask for dog,

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I'll get d-d-o-o-g-g-. See you next time.