Promotes a non-strict value to a Coeval.

Alias of eval.

Given an A type that has a cats.Semigroup[A] implementation, then this provides the evidence that Coeval[A] also has a Semigroup[Coeval[A]] implementation.

This has a lower-level priority than Coeval.catsMonoid in order to avoid conflicts.

Promote a non-strict value to a Coeval, catching exceptions in the process.

Note that since Coeval is not memoized, this will recompute the value each time the Coeval is executed.

Promote a non-strict value to a Coeval that is memoized on the first evaluation, the result being then available on subsequent evaluations.

Guarantees thread-safe idempotency.

UNSAFE — this operation allocates a shared, mutable reference, which can break in certain cases referential transparency, even if this operation guarantees idempotency (i.e. referential transparency implies idempotency, but idempotency does not imply referential transparency).

The allocation of a mutable reference is known to be a side effect, thus breaking referential transparency, even if calling this method does not trigger the evaluation of side effects suspended by the source.

Use with care. Sometimes it's easier to just keep a shared, memoized reference to some connection, but keep in mind it might be better to pass such a reference around as a parameter.

Converts a Scala Either into a Coeval.

Returns a F ~> Coeval (FunctionK) for transforming any supported data-type into Coeval.

Useful for mapK transformations, for example when working with Resource or Iterant:

import cats.effect._
import monix.eval._
import java.io._

def open(file: File) =
  Resource[SyncIO, InputStream](SyncIO {
    val in = new FileInputStream(file)
    (in, SyncIO(in.close()))
  })

// Lifting to a Resource of Coeval
val res: Resource[Coeval, InputStream] =
  open(new File("sample")).mapK(Coeval.liftFrom[SyncIO])

See cats.arrow.FunctionK.

Generates Coeval ~> F (FunctionK) values for converting from Coeval to supporting types (for which we have a CoevalLift instance).

See the documentation.

import cats.effect._
import monix.eval._
import java.io._

def open(file: File) =
  Resource[Coeval, InputStream](Coeval {
    val in = new FileInputStream(file)
    (in, Coeval(in.close()))
  })

// Lifting to a Resource of Task
val res: Resource[Task, InputStream] =
  open(new File("sample")).mapK(Coeval.liftTo[Task])

// This was needed in order to process the resource
// with a Task, instead of a Coeval
res.use { in =>
  Task {
    in.read()
  }
}

Generates Coeval ~> F function values (FunctionK) for converting from Coeval to types for which we have a cats.effect.Sync instance.

Pairs 2 Coeval values, applying the given mapping function.

Returns a new Coeval reference that completes with the result of mapping that function to their successful results, or in failure in case either of them fails.

val fa1 = Coeval(1)
val fa2 = Coeval(2)

// Yields Success(3)
Coeval.map2(fa1, fa2) { (a, b) =>
  a + b
}

// Yields Failure(e), because the second arg is a failure
Coeval.map2(fa1, Coeval.raiseError[Int](new RuntimeException("boo"))) { (a, b) =>
  a + b
}

Pairs 3 Coeval values, applying the given mapping function.

Returns a new Coeval reference that completes with the result of mapping that function to their successful results, or in failure in case either of them fails.

val fa1 = Coeval(1)
val fa2 = Coeval(2)
val fa3 = Coeval(3)

// Yields Success(6)
Coeval.map3(fa1, fa2, fa3) { (a, b, c) =>
  a + b + c
}

// Yields Failure(e), because the second arg is a failure
Coeval.map3(fa1, Coeval.raiseError[Int](new RuntimeException("boo")), fa3) { (a, b, c) =>
  a + b + c
}

Pairs 4 Coeval values, applying the given mapping function.

Returns a new Coeval reference that completes with the result of mapping that function to their successful results, or in failure in case either of them fails.

val fa1 = Coeval(1)
val fa2 = Coeval(2)
val fa3 = Coeval(3)
val fa4 = Coeval(4)

// Yields Success(10)
Coeval.map4(fa1, fa2, fa3, fa4) { (a, b, c, d) =>
  a + b + c + d
}

// Yields Failure(e), because the second arg is a failure
Coeval.map4(fa1, Coeval.raiseError[Int](new RuntimeException("boo")), fa3, fa4) {
  (a, b, c, d) => a + b + c + d
}

Pairs 5 Coeval values, applying the given mapping function.

Returns a new Coeval reference that completes with the result of mapping that function to their successful results, or in failure in case either of them fails.

val fa1 = Coeval(1)
val fa2 = Coeval(2)
val fa3 = Coeval(3)
val fa4 = Coeval(4)
val fa5 = Coeval(5)

// Yields Success(15)
Coeval.map5(fa1, fa2, fa3, fa4, fa5) { (a, b, c, d, e) =>
  a + b + c + d + e
}

// Yields Failure(e), because the second arg is a failure
Coeval.map5(fa1, Coeval.raiseError[Int](new RuntimeException("boo")), fa3, fa4, fa5) {
  (a, b, c, d, e) => a + b + c + d + e
}

Pairs 6 Coeval values, applying the given mapping function.

Returns a new Coeval reference that completes with the result of mapping that function to their successful results, or in failure in case either of them fails.

val fa1 = Coeval(1)
val fa2 = Coeval(2)
val fa3 = Coeval(3)
val fa4 = Coeval(4)
val fa5 = Coeval(5)
val fa6 = Coeval(6)

// Yields Success(21)
Coeval.map6(fa1, fa2, fa3, fa4, fa5, fa6) { (a, b, c, d, e, f) =>
  a + b + c + d + e + f
}

// Yields Failure(e), because the second arg is a failure
Coeval.map6(fa1, Coeval.raiseError[Int](new RuntimeException("boo")), fa3, fa4, fa5, fa6) {
  (a, b, c, d, e, f) => a + b + c + d + e + f
}

Lifts a value into the coeval context. Alias for now.

Returns raiseError when cond is false, otherwise Coeval.unit

Returns raiseError when the cond is true, otherwise Coeval.unit

Transforms a Iterable of coevals into a coeval producing the same collection of gathered results.

It's a simple version of traverse.

Keeps calling f until it returns a Right result.

Based on Phil Freeman's Stack Safety for Free.

Transforms a Iterable[A] into a coeval of the same collection using the provided function A => Coeval[B].

It's a generalized version of sequence.

Returns the given argument if cond is false, otherwise Coeval.Unit

Returns the given argument if cond is true, otherwise Coeval.Unit

DEPRECATED — please switch to Coeval.from.

DEPRECATED — please switch to Coeval.from.