Incorrect Float conversion by Argonaut.io

Question

I convert Float field of object to json. And value 0.6 converts to 0.6000000238418579 by Argonaut. How to correct it?

Simple test case to check this:

import argonaut.Argonaut._
import argonaut.EncodeJson

class Person(val name: Float)
val person = new Person(0.6f)
println("#1")
println(person.name)
def PersonEncodeJson: EncodeJson[Person] =
  EncodeJson((p: Person) => ("name" := p.name) ->: jEmptyObject)
val json = person.asJson(PersonEncodeJson).nospaces
println("#2")
println(json)

Console output:

#1
0.6
#2
{"name":0.6000000238418579}

Answer 1

Do you have to be using Float? Since you care about the exact value, it doesn't seem appropriate.

Example using BigDecimal instead:

import argonaut.Argonaut._
import argonaut.EncodeJson

class Person(val name: BigDecimal)
val person = new Person(BigDecimal("0.6"))

def PersonEncodeJson: EncodeJson[Person] =
  EncodeJson((p: Person) => ("name" := p.name) ->: jEmptyObject)

person.asJson(PersonEncodeJson).nospaces
// res0: String = {"name":0.6}

Or if you can't change the Person class, you can convert the Float to String and then to BigDecimal:

import argonaut.Argonaut._
import argonaut.EncodeJson

class Person(val name: Float)
val person = new Person(0.6f)

def PersonEncodeJson: EncodeJson[Person] =
  EncodeJson((p: Person) =>
    ("name" := BigDecimal(p.name.toString)) ->: jEmptyObject)

person.asJson(PersonEncodeJson).nospaces
// res0: String = {"name":0.6}