## 03-13 Statements Solution

• 0:00 - 0:03
All right, let's go over the possible answers together.
• 0:03 - 0:07
We say that a statement has to be an identifier followed by an equals sign
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followed by an expression.
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Lata, l-a-t-a, is definitely an identifier using our previous rules.
• 0:13 - 0:17
That's a collection of upper and lower case letters that may include an underscore,
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but the underscore can't come first.
• 0:19 - 0:23
This is an identifier, and expression can go directly to number,
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and 1 is a number, so this is totally valid.
• 0:26 - 0:30
Here we have Mangeshkar = 19 + 29.
• 0:30 - 0:34
Well, Mangeshkar is longer, but it's still an identifier.
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It's a collection of letters, and it may have underscores, but it doesn't.
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And then we have the equals sign. That matches.
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And now we're going to use this rule here, expression goes to expression + expression
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to get this + sign, and then expression will go to number for 19,
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and expression will go to number for 29.
• 0:51 - 0:53
I like this.
• 0:53 - 0:55
Here we have Lata = Lata + 1.
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This one is tricky because it's totally valid in Python,
• 0:59 - 1:03
but it's not valid in this grammar.
• 1:03 - 1:06
I haven't said that expression can go to identifier,
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so Lata is an identifier.
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The equals sign is an equals sign.
• 1:10 - 1:14
But over here I need something like 1 + 1.
• 1:14 - 1:19
I don't yet have a rule that would allow me to have Lata + 1.
• 1:19 - 1:23
If I had this mysterious fifth rule, then this would be in the language of the grammar.
• 1:23 - 1:26
But I don't yet, so it isn't.
• 1:26 - 1:30
And then over here, Mangeshkar = 25,000 - 1,
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that's an identifier =,
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and now we're going to use this rule here, expression - expression.
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This totally works out.
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Lata Mangeshkar is a famous Indian playback singer.
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She's recorded over 25,000 songs,
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a world record for quite some time, and she's also received India's highest civilian honor.
Title:
03-13 Statements Solution
Description:

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Video Language:
English
Team:
Udacity
Project:
CS262 - Programming Languages
Duration:
01:51
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