Kotlin Conflicting declarations: val sinAngle: Float, val sinAngle: Float-CodePudding

I have a data class and function:

data class SinCosAngle(val sa: Float, val ca: Float)

fun angleCalc(rad: Float): SinCosAngle {
    return SinCosAngle(sin(rad), cos(rad))
}

I want to use the function multiple times like:

for (i in 0..72) {
    val (sinAngle, cosAngle) = angleCalc(deg2rad(i * 5f - 90f)) // 1
    (...)
    canvas.drawLine(x1, y1, x2, y2, paint)
}
paint.strokeWidth = 3f
for (i in 0..8) {
    val (sinAngle, cosAngle) = angleCalc(deg2rad(i * 45f - 90f)) // 2
    (...)
    canvas.drawLine(x1, y1, x2, y2, paint)
}

val (sinAngle, cosAngle) = angleCalc(deg2rad(course - 90f)) // 3
(...)

val (sinAngle, cosAngle) = angleCalc(deg2rad(course - 90f - angleArrow)) // 4
(...)

val (sinAngle, cosAngle) = angleCalc(deg2rad(course - 90f   angleArrow)) // 5
(...)

I got errors only at lines 3,4,5. Lines 1 and 2 are OK.

Conflicting declarations: val sinAngle: Float, val sinAngle: Float

I can fix errors by changing the variable names at lines 3 and 4 but line 5 can remain unchanged.

Working code:

for (i in 0..72) {
    val (sinAngle, cosAngle) = angleCalc(deg2rad(i * 5f - 90f))
    x1 = x   cosAngle * radius
    y1 = y   sinAngle * radius
    x2 = x   cosAngle * radiusShort
    y2 = y   sinAngle * radiusShort
    canvas.drawLine(x1, y1, x2, y2, paint)
}
paint.strokeWidth = 3f
for (i in 0..8) {
    val (sinAngle, cosAngle) = angleCalc(deg2rad(i * 45f - 90f))
    x1 = x   cosAngle * radius
    y1 = y   sinAngle * radius
    x2 = x   cosAngle * radiusShort
    y2 = y   sinAngle * radiusShort
    canvas.drawLine(x1, y1, x2, y2, paint)
}
(...)
paint.strokeWidth = 2f
paint.color = getColor(R.color.red)
val (sinAngle1, cosAngle1) = angleCalc(deg2rad(course - 90f))
x2 = x   cosAngle1 * radiusCourse
y2 = y   sinAngle1 * radiusCourse
canvas.drawLine(x, y, x2, y2, paint)
x1 = x   cosAngle1 * radius
y1 = y   sinAngle1 * radius
canvas.drawCircle(x1, y1, smallCircleRadius, paint)
val (sinAngle2, cosAngle2) = angleCalc(deg2rad(course - 90f - angleArrow))
x1 = x2 - cosAngle2 * radiusArrow
y1 = y2 - sinAngle2 * radiusArrow
canvas.drawLine(x1, y1, x2, y2, paint)
val (sinAngle, cosAngle) = angleCalc(deg2rad(course - 90f   angleArrow))
x1 = x2 - cosAngle * radiusArrow
y1 = y2 - sinAngle * radiusArrow
canvas.drawLine(x1, y1, x2, y2, paint)

How to propertly use the same val name in this case ?

(Android Studio 2020.3.1 Patch 3 October 1, 2021)

CodePudding user response：

If you want to still use the same name for the variables, you can introduce a new scope with scope functions. For example, putting each declaration in a run block

run {
    val (sinAngle, cosAngle) = angleCalc(deg2rad(course - 90f))
    // use the angles here
}
run {
    val (sinAngle, cosAngle) = angleCalc(deg2rad(course - 90f - angleArrow))
    // use the angles here
}
run {
    val (sinAngle, cosAngle) = angleCalc(deg2rad(course - 90f   angleArrow))
    // use the angles here
}

I find let more readable:

angleCalc(deg2rad(course - 90f)).let { (sinAngle, cosAngle) ->
    // use the angles here
}

angleCalc(deg2rad(course - 90f - angleArrow)).let { (sinAngle, cosAngle) ->
    // use the angles here
}

angleCalc(deg2rad(course - 90f   angleArrow)).let { (sinAngle, cosAngle) ->
    // use the angles here
}

However, you cannot reuse the same property, unless you give up on using the destructuring syntax:

var angles = angleCalc(deg2rad(course - 90f))
// use the angles here

// reusing the variable, without destructuring
angles = angleCalc(deg2rad(course - 90f - angleArrow))

Destructuring only works when you declare a property. The full name of this feature is called "Destructuring Declarations"

CodePudding user response：

You can't do that. You can not have two variables with same name in the same scope.

Lines 1 and 2 are working because those variable are in the scope of for loop. Lines 3, 4 and 5 are in the same scope that's why you can't use the same variable name in these lines.

One way could be to use a var for the radian angle (similar to how you are using x1, y1 etc.):

var angle = deg2rad(course - 90f)
x2 = x   cos(angle) * radiusCourse
y2 = y   sin(angle) * radiusCourse
canvas.drawLine(x, y, x2, y2, paint)

angle = deg2rad(course - 90f - angleArrow)
x1 = x2 - cos(angle) * radiusArrow
y1 = y2 - sin(angle) * radiusArrow
canvas.drawLine(x1, y1, x2, y2, paint)

and so on...

This one does look a little cleaner :)