Packages

trait Evals extends AnyRef

EXPERIMENTAL

A slice of the Scala macros context that provides a facility to evaluate trees.

Self Type
blackbox.Context
Source
Evals.scala
Linear Supertypes
AnyRef, Any
Known Subclasses
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Inherited
  1. Evals
  2. AnyRef
  3. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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Visibility
  1. Public
  2. All

Abstract Value Members

  1. abstract def eval[T](expr: blackbox.Context.Expr[T]): T

    Takes a typed wrapper for a tree of type T and evaluates it to a value of type T.

    Takes a typed wrapper for a tree of type T and evaluates it to a value of type T.

    Can be used to perform compile-time computations on macro arguments to the extent permitted by the shape of the arguments.

    Known issues: because of https://github.com/scala/bug/issues/5748 trees being evaluated first need to undergo untypecheck. Resetting symbols and types mutates the tree in place, therefore the conventional approach is to duplicate the tree first.

    scala> def impl(c: Context)(x: c.Expr[String]) = {
         | val x1 = c.Expr[String](c.untypecheck(x.tree.duplicate))
         | println(s"compile-time value is: ${c.eval(x1)}")
         | x
         | }
    impl: (c: Context)(x: c.Expr[String])c.Expr[String]
    
    scala> def test(x: String) = macro impl
    test: (x: String)String
    
    scala> test("x")
    compile-time value is: x
    res0: String = x
    
    scala> test("x" + "y")
    compile-time value is: xy
    res1: String = xy
    
    scala> val x = "x"
    x: String = x
    
    scala> test(x + "y")
    compile-time value is: xy
    res2: String = xy
    
    scala> { val x = "x"; test(x + "y") }
    error: exception during macro expansion:
    scala.tools.reflect.ToolBoxError: reflective compilation failed

    Note that in the last case evaluation has failed, because the argument of a macro refers to a runtime value x, which is unknown at compile time.

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##(): Int
    Definition Classes
    AnyRef → Any
  3. def +(other: String): String
    Implicit
    This member is added by an implicit conversion from Evals to any2stringadd[Evals] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  4. def ->[B](y: B): (Evals, B)
    Implicit
    This member is added by an implicit conversion from Evals to ArrowAssoc[Evals] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  5. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  6. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  7. def clone(): AnyRef
    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @native() @throws( ... )
  8. def ensuring(cond: (Evals) ⇒ Boolean, msg: ⇒ Any): Evals
    Implicit
    This member is added by an implicit conversion from Evals to Ensuring[Evals] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  9. def ensuring(cond: (Evals) ⇒ Boolean): Evals
    Implicit
    This member is added by an implicit conversion from Evals to Ensuring[Evals] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  10. def ensuring(cond: Boolean, msg: ⇒ Any): Evals
    Implicit
    This member is added by an implicit conversion from Evals to Ensuring[Evals] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  11. def ensuring(cond: Boolean): Evals
    Implicit
    This member is added by an implicit conversion from Evals to Ensuring[Evals] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  12. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  13. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  14. def finalize(): Unit
    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  15. def formatted(fmtstr: String): String
    Implicit
    This member is added by an implicit conversion from Evals to StringFormat[Evals] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  16. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  17. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  18. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  19. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  20. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  21. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  22. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  23. def toString(): String
    Definition Classes
    AnyRef → Any
  24. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  25. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  26. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @throws( ... )
  27. def [B](y: B): (Evals, B)
    Implicit
    This member is added by an implicit conversion from Evals to ArrowAssoc[Evals] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd from Evals to any2stringadd[Evals]

Inherited by implicit conversion StringFormat from Evals to StringFormat[Evals]

Inherited by implicit conversion Ensuring from Evals to Ensuring[Evals]

Inherited by implicit conversion ArrowAssoc from Evals to ArrowAssoc[Evals]

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