Simple methods in Scala

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July 15th, 2010, 08:28 PM

Fewmitz

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Simple methods in Scala

"Write a method called squares that takes an integer as its only argument and returns a list of integers that are the squares of the integer up and including the integer argument"

I'm new to Scala, so I'm a little confused on what to do. This is what I have so far:

Code:

	def squares(num: Int): List[Int] ={
		var inc:Int = 1
		var squares:List[Int] = List()
		while(inc <= num){
			var temp = inc*inc
			squares += temp
			//inc += 1
		}
		return squares

	}

From what I understand, += can be used to append to a list, but I'm getting a compiler error at that line: type mismatch; found: Inc required: String

But my list is defined as an Int.

I don't understand.

July 16th, 2010, 05:55 AM

OmegaZero

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That code compiles fine for me.

Cut & paste the EXACT code you're trying to compile and the EXACT error message from the compiler.

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July 17th, 2010, 09:03 AM

Fewmitz

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Quote:

Originally Posted by OmegaZero

That code compiles fine for me.

Cut & paste the EXACT code you're trying to compile and the EXACT error message from the compiler.

Code:

class Part1{

       //...other working methods...
	def squares(num: Int): List[Int] ={
		var inc:Int = 1
		var squares:List[Int] = List()
		while(inc <= num){
			var temp = inc*inc
			squares += temp
			//inc += 1
		}
		return squares

	}
}

object P2 {
	
	def main(args: Array[String]){
		val obj = new Part1
		var sq = List[Int]()
		sq = obj.squares(4)

	}
}

I'm in Eclipse, and temp's underlined:

type mismatch; found: Int required: String

July 17th, 2010, 09:34 AM

OmegaZero

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I have no problem building & running that code from the command line.

What version of scala are you using?

July 17th, 2010, 09:43 AM

Fewmitz

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I don't remember the version number specifically, but it's the latest stable build. I loaded it a few days ago.

Though I'm wondering if the installation went wrong or something; I'm having trouble importing Trees, too.

July 17th, 2010, 11:27 AM

OmegaZero

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Ah. Try :+ instead of +. + was deprecated and if I'm not mistaken was finally removed in 2.8

July 17th, 2010, 04:20 PM

Fewmitz

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Code:

	def squares(num: Int): List[Int] ={
		var inc:Int = 1
		var squares:List[Int] = List()
		while(inc <= num){
			var temp = inc*inc
			squares :+ temp
			inc += 1
		}
		return squares

	}

Compiles, but it doesn't look like there's anything in squares after the method finishes; accessing squares(1) throws an IndexOutOfBoundsException.

Thanks for all the help so far.

July 18th, 2010, 08:26 AM

OmegaZero

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You never assign the result of "squares :+ temp" anywhere so you're returning the original (empty) list.

Simple methods in Scala

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