gapt.provers.viper.grammars.randomInstance.scala Maven / Gradle / Ivy

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General Architecture for Proof Theory

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package gapt.provers.viper.grammars

import gapt.expr._
import gapt.expr.formula.fol.folTermSize
import gapt.expr.ty.FunctionType
import gapt.expr.ty.TBase
import gapt.proofs.context.Context
import gapt.utils.NameGenerator

import scala.util.Random

object randomInstance {

  def generate(tys: Seq[TBase])(implicit ctx: Context): Seq[Expr] = {
    val nameGen = new NameGenerator(Set())
    tys.map(generate(_, nameGen))
  }
  def generate(ty: TBase)(implicit ctx: Context): Expr = generate(ty, new NameGenerator(Set()))

  def generate(ty: TBase, nameGen: NameGenerator)(implicit ctx: Context): Expr = {
    ctx.getConstructors(ty) match {
      case None =>
        Var(nameGen freshWithIndex "x", ty)
      case Some(ctrs) =>
        val ctr = ctrs(Random.nextInt(ctrs.size))
        val FunctionType(_, argTypes) = ctr.ty: @unchecked
        val args = argTypes.map { at => generate(at.asInstanceOf[TBase], nameGen) }
        ctr(args: _*)
    }
  }

  def generate(tys: Seq[TBase], cond: Float => Boolean)(implicit ctx: Context): Seq[Expr] =
    LazyList.continually(generate(tys)).filter(insts => cond(folTermSize(insts).toFloat / insts.size)).head

}