Scala - 错误：未找到：值
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scala - error: not found: value
提问by nazar_art
I newly at scala and tried to pass some easy scala worksheet.
我刚加入 Scala 并试图通过一些简单的 Scala 工作表。
IDE is Intellij IDEA community edition and OS Ubuntu 12.04, sbtwas installed correctly.
IDE 是 Intellij IDEA 社区版和 OS Ubuntu 12.04，sbt已正确安装。
But it throws error - error: not found: value
但它抛出错误 - error: not found: value
OI can't understand why this happen:
OI 不明白为什么会发生这种情况：
Code:
代码：
object session {
1 + 2
def abs(x: Double) = if (x < 0) -x else x <== update this line
def sqrtIter(guess: Double, x: Double): Double =
if (isGoodEnough(guess, x)) guess
else sqrtIter(improve(guess, x), x)
def isGoodEnough(guess: Double, x: Double) =
abs(guess * guess - x) < 0.001
def improve(guess: Double, x: Double) =
(guess + x / guess) / 2
def sqrt(x: Double) = sqrtIter(1.0, x)
sqrt(2)
sqrt(4)
}
Output from right side of screen:
屏幕右侧的输出：
> res0: Int = 3
> <console>:8: error: not found: value isGoodEnough
if (isGoodEnough(guess, x)) guess else sqrtIter(improve(guess, x), x)
^
<console>:8: error: not found: value improve
if (isGoodEnough(guess, x)) guess else sqrtIter(improve(guess, x), x)
^
> <console>:8: error: not found: value abs
abs(guess * guess - x) < 0.001
^
> improve: (guess: Double, x: Double)Double
> <console>:7: error: not found: value sqrtIter
def sqrt(x: Double) = sqrtIter(1.0, x)
^
> <console>:8: error: not found: value sqrt
sqrt(2)
^
> <console>:8: error: not found: value sqrt
sqrt(4)
Any suggestions?
有什么建议？
回答by Shadowlands
The complete error message is error: not found: value abs. The value "abs" wan't found. You want math.abs. Alternatively you could add import math._somewhere before you need these math functions.
完整的错误信息是error: not found: value abs。未找到值“abs”。你要math.abs。或者，您可以import math._在需要这些数学函数之前在某处添加。
回答by lpm_nova
I had the same problem as you. I didn't think importing math.abs or importing math._ were valid as abs was defined in the code.
我和你有同样的问题。我不认为导入 math.abs 或导入 math._ 是有效的，因为 abs 是在代码中定义的。
What worked for me was reorganizing the order of the function definitions. You have to define something above before it can be used below.
对我有用的是重新组织函数定义的顺序。你必须在上面定义一些东西才能在下面使用它。
object session {
def abs(x: Double) = if (x<0) - x else x
def isGoodEnough(guess: Double, x: Double) =
abs(guess * guess - x) < 0.001
def improve(guess: Double, x: Double) =
(guess + x / guess) / 2
def sqrtIter(guess: Double, x: Double): Double =
if(isGoodEnough(guess, x)) guess
else sqrtIter(improve(guess, x), x)
def sqrt(x: Double) = { sqrtIter(1.0, x) }
sqrt(2)
sqrt(4)
}
Returned:
回：
> abs: (x: Double)Double
> isGoodEnough: (guess: Double, x: Double)Boolean
> improve: (guess: Double, x: Double)Double
> sqrtIter: (guess: Double, x: Double)Double
> sqrt: (x: Double)Double
> res0: Double = 1.4142156862745097
> res1: Double = 2.0000000929222947
回答by nazar_art
And some easiest way without redundant code:
还有一些没有冗余代码的最简单方法：
object session {
1 + 2
def abs(x: Double) = if (x < 0) -x else x
def sqrt(x: Double) = {
def sqrtIter(guess: Double): Double =
if (isGoodEnough(guess)) guess
else sqrtIter(improve(guess))
def isGoodEnough(guess: Double) =
abs(guess * guess - x) / x < 0.001
def improve(guess: Double) =
(guess + x / guess) / 2
sqrtIter(1.0)
}
sqrt(2)
sqrt(4)
sqrt(1e-16)
sqrt(1e60)
}
