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package monocle.state
import cats.{Eval, Now}
import monocle.PLens
import cats.data.{IndexedStateT, State}
trait StateLensSyntax {
implicit def toStateLensOps[S, T, A, B](lens: PLens[S, T, A, B]): StateLensOps[S, T, A, B] =
new StateLensOps[S, T, A, B](lens)
}
final class StateLensOps[S, T, A, B](private val lens: PLens[S, T, A, B]) extends AnyVal {
/** transforms a PLens into a State */
def toState: State[S, A] =
State(s => (s, lens.get(s)))
/** alias for toState */
def st: State[S, A] =
toState
/** extracts the value viewed through the lens */
def extract: State[S, A] =
toState
/** extracts the value viewed through the lens and applies `f` over it */
def extracts[B](f: A => B): State[S, B] =
extract.map(f)
/** modify the value viewed through the lens and returns its *new* value */
def mod(f: A => B): IndexedStateT[Eval, S, T, B] =
IndexedStateT { s =>
val a = lens.get(s)
val b = f(a)
Now((lens.set(b)(s), b))
}
/** modify the value viewed through the lens and returns its *old* value */
def modo(f: A => B): IndexedStateT[Eval, S, T, A] =
toState.bimap(lens.modify(f), identity)
/** modify the value viewed through the lens and ignores both values */
def mod_(f: A => B): IndexedStateT[Eval, S, T, Unit] =
IndexedStateT(s => Now((lens.modify(f)(s), ())))
/** set the value viewed through the lens and returns its *new* value */
def assign(b: B): IndexedStateT[Eval, S, T, B] =
mod(_ => b)
/** set the value viewed through the lens and returns its *old* value */
def assigno(b: B): IndexedStateT[Eval, S, T, A] =
modo(_ => b)
/** set the value viewed through the lens and ignores both values */
def assign_(b: B): IndexedStateT[Eval, S, T, Unit] =
mod_(_ => b)
}
