E4138

Range operators only support builtin integer types, they cannot be used on this type.

错误示例

For example, you cannot use Float nor Double with range operators.

fn main {
  for f in 0.0..<1.0 {
  }
}

建议

Use integer types for the range operators, and genearte floats from these integers instead:

fn main {
  for i in 0..<10 {
    println(i.to_float())
  }
}

You can also use until to construct a range of numbers:

fn main {
  let range : Iter[Double] = (0.0).until(10.0)
  for i in range {
    println(i)
  }
}