Rectangle 27 33

Swift 3 - making use of the rounded(_:) method as blueprinted in the F...

FloatingPoint
Double
Float
func rounded(_ rule: FloatingPointRoundingRule) -> Self

Where FloatingPointRoundingRule is an enum enumerating a number of different rounding rules:

case awayFromZero
case down
case toNearestOrAwayFromZero
case toNearestOrEven
case towardZero
case up

We make use of similar examples to the ones from @Suragch's excellent answer to show these different rounding options in practice.

3.000.rounded(.awayFromZero) // 3.0
3.001.rounded(.awayFromZero) // 4.0
3.999.rounded(.awayFromZero) // 4.0

(-3.000).rounded(.awayFromZero) // -3.0
(-3.001).rounded(.awayFromZero) // -4.0
(-3.999).rounded(.awayFromZero) // -4.0
floor
3.000.rounded(.down) // 3.0
3.001.rounded(.down) // 3.0
3.999.rounded(.down) // 3.0

(-3.000).rounded(.down) // -3.0
(-3.001).rounded(.down) // -4.0
(-3.999).rounded(.down) // -4.0
round
3.000.rounded(.toNearestOrAwayFromZero) // 3.0
3.001.rounded(.toNearestOrAwayFromZero) // 3.0
3.499.rounded(.toNearestOrAwayFromZero) // 3.0
3.500.rounded(.toNearestOrAwayFromZero) // 4.0
3.999.rounded(.toNearestOrAwayFromZero) // 4.0

(-3.000).rounded(.toNearestOrAwayFromZero) // -3.0
(-3.001).rounded(.toNearestOrAwayFromZero) // -3.0
(-3.499).rounded(.toNearestOrAwayFromZero) // -3.0
(-3.500).rounded(.toNearestOrAwayFromZero) // -4.0
(-3.999).rounded(.toNearestOrAwayFromZero) // -4.0

This rounding rule can also be accessed using the zero argument rounded() method.

3.000.rounded() // 3.0
// ...

(-3.000).rounded() // -3.0
// ...

Round to the closest allowed value; if two values are equally close, the even one is chosen; equivalent to the C rint (/very similar to nearbyint) function.

3.499.rounded(.toNearestOrEven) // 3.0
3.500.rounded(.toNearestOrEven) // 4.0 (up to even)
3.501.rounded(.toNearestOrEven) // 4.0

4.499.rounded(.toNearestOrEven) // 4.0
4.500.rounded(.toNearestOrEven) // 4.0 (down to even)
4.501.rounded(.toNearestOrEven) // 4.0
trunc
3.000.rounded(.towardZero) // 3.0
3.001.rounded(.towardZero) // 3.0
3.999.rounded(.towardZero) // 3.0

(-3.000).rounded(.towardZero) // 3.0
(-3.001).rounded(.towardZero) // 3.0
(-3.999).rounded(.towardZero) // 3.0

If the purpose of the rounding is to prepare to work with an integer (e.g. using Int by FloatPoint initialization after rounding), we might simply make use of the fact that when initializing an Int using a Double (or Float etc), the decimal part will be truncated away.

Int(3.000) // 3
Int(3.001) // 3
Int(3.999) // 3

Int(-3.000) // -3
Int(-3.001) // -3
Int(-3.999) // -3
ceil
3.000.rounded(.up) // 3.0
3.001.rounded(.up) // 4.0
3.999.rounded(.up) // 4.0

(-3.000).rounded(.up) // 3.0
(-3.001).rounded(.up) // 3.0
(-3.999).rounded(.up) // 3.0

If we'd like, we can take a look at the source code for FloatingPoint protocol to directly see the C function equivalents to the public FloatingPointRoundingRule rules.

rounded(_:)
public func rounded(_ rule: FloatingPointRoundingRule) -> Self {
    var lhs = self
    lhs.round(rule)
    return lhs
}
round(_:)
FloatingPointRoundingRule
public mutating func round(_ rule: FloatingPointRoundingRule) {
    switch rule {
    case .toNearestOrAwayFromZero:
        _value = Builtin.int_round_FPIEEE${bits}(_value)
    case .toNearestOrEven:
        _value = Builtin.int_rint_FPIEEE${bits}(_value)
    case .towardZero:
        _value = Builtin.int_trunc_FPIEEE${bits}(_value)
    case .awayFromZero:
        if sign == .minus {
            _value = Builtin.int_floor_FPIEEE${bits}(_value)
        }
        else {
            _value = Builtin.int_ceil_FPIEEE${bits}(_value)
        }
    case .up:
        _value = Builtin.int_ceil_FPIEEE${bits}(_value)
    case .down:
        _value = Builtin.int_floor_FPIEEE${bits}(_value)
    }
}

@Suragch thanks! Fully inspired by your excellent answer though (but with the new Swift 3 alternatives), so I shouldn't take too much credit :) btw, you might want to mention also rint: it's the Darwin equivalent to FloatingPoint's .toNearestOrEven. Also, I noticed the link in the bottom of your answer has been broken; an appropriate alternative is possible these Darwin man. pages.

How to round a Double to the nearest Int in swift? - Stack Overflow

swift int double rounding
Rectangle 27 0

Swift 3 - making use of the rounded(_:) method as blueprinted in the F...

FloatingPoint
Double
Float
func rounded(_ rule: FloatingPointRoundingRule) -> Self

Where FloatingPointRoundingRule is an enum enumerating a number of different rounding rules:

case awayFromZero
case down
case toNearestOrAwayFromZero
case toNearestOrEven
case towardZero
case up

We make use of similar examples to the ones from @Suragch's excellent answer to show these different rounding options in practice.

3.000.rounded(.awayFromZero) // 3.0
3.001.rounded(.awayFromZero) // 4.0
3.999.rounded(.awayFromZero) // 4.0

(-3.000).rounded(.awayFromZero) // -3.0
(-3.001).rounded(.awayFromZero) // -4.0
(-3.999).rounded(.awayFromZero) // -4.0
floor
3.000.rounded(.down) // 3.0
3.001.rounded(.down) // 3.0
3.999.rounded(.down) // 3.0

(-3.000).rounded(.down) // -3.0
(-3.001).rounded(.down) // -4.0
(-3.999).rounded(.down) // -4.0
round
3.000.rounded(.toNearestOrAwayFromZero) // 3.0
3.001.rounded(.toNearestOrAwayFromZero) // 3.0
3.499.rounded(.toNearestOrAwayFromZero) // 3.0
3.500.rounded(.toNearestOrAwayFromZero) // 4.0
3.999.rounded(.toNearestOrAwayFromZero) // 4.0

(-3.000).rounded(.toNearestOrAwayFromZero) // -3.0
(-3.001).rounded(.toNearestOrAwayFromZero) // -3.0
(-3.499).rounded(.toNearestOrAwayFromZero) // -3.0
(-3.500).rounded(.toNearestOrAwayFromZero) // -4.0
(-3.999).rounded(.toNearestOrAwayFromZero) // -4.0

This rounding rule can also be accessed using the zero argument rounded() method.

3.000.rounded() // 3.0
// ...

(-3.000).rounded() // -3.0
// ...

Round to the closest allowed value; if two values are equally close, the even one is chosen; equivalent to the C rint (/very similar to nearbyint) function.

3.499.rounded(.toNearestOrEven) // 3.0
3.500.rounded(.toNearestOrEven) // 4.0 (up to even)
3.501.rounded(.toNearestOrEven) // 4.0

4.499.rounded(.toNearestOrEven) // 4.0
4.500.rounded(.toNearestOrEven) // 4.0 (down to even)
4.501.rounded(.toNearestOrEven) // 4.0
trunc
3.000.rounded(.towardZero) // 3.0
3.001.rounded(.towardZero) // 3.0
3.999.rounded(.towardZero) // 3.0

(-3.000).rounded(.towardZero) // 3.0
(-3.001).rounded(.towardZero) // 3.0
(-3.999).rounded(.towardZero) // 3.0

If the purpose of the rounding is to prepare to work with an integer (e.g. using Int by FloatPoint initialization after rounding), we might simply make use of the fact that when initializing an Int using a Double (or Float etc), the decimal part will be truncated away.

Int(3.000) // 3
Int(3.001) // 3
Int(3.999) // 3

Int(-3.000) // -3
Int(-3.001) // -3
Int(-3.999) // -3
ceil
3.000.rounded(.up) // 3.0
3.001.rounded(.up) // 4.0
3.999.rounded(.up) // 4.0

(-3.000).rounded(.up) // 3.0
(-3.001).rounded(.up) // 3.0
(-3.999).rounded(.up) // 3.0

If we'd like, we can take a look at the source code for FloatingPoint protocol to directly see the C function equivalents to the public FloatingPointRoundingRule rules.

rounded(_:)
public func rounded(_ rule: FloatingPointRoundingRule) -> Self {
    var lhs = self
    lhs.round(rule)
    return lhs
}
round(_:)
FloatingPointRoundingRule
public mutating func round(_ rule: FloatingPointRoundingRule) {
    switch rule {
    case .toNearestOrAwayFromZero:
        _value = Builtin.int_round_FPIEEE${bits}(_value)
    case .toNearestOrEven:
        _value = Builtin.int_rint_FPIEEE${bits}(_value)
    case .towardZero:
        _value = Builtin.int_trunc_FPIEEE${bits}(_value)
    case .awayFromZero:
        if sign == .minus {
            _value = Builtin.int_floor_FPIEEE${bits}(_value)
        }
        else {
            _value = Builtin.int_ceil_FPIEEE${bits}(_value)
        }
    case .up:
        _value = Builtin.int_ceil_FPIEEE${bits}(_value)
    case .down:
        _value = Builtin.int_floor_FPIEEE${bits}(_value)
    }
}

@Suragch thanks! Fully inspired by your excellent answer though (but with the new Swift 3 alternatives), so I shouldn't take too much credit :) btw, you might want to mention also rint: it's the Darwin equivalent to FloatingPoint's .toNearestOrEven. Also, I noticed the link in the bottom of your answer has been broken; an appropriate alternative is possible these Darwin man. pages.

How to round a Double to the nearest Int in swift? - Stack Overflow

swift int double rounding