simpleSubset = (sub, dom, options) => {
  if (sub === dom) {
    return true
  }

  if (sub.length === 1 && sub[0].semver === ANY) {
    if (dom.length === 1 && dom[0].semver === ANY) {
      return true
    } else if (options.includePrerelease) {
      sub = [new Comparator('>=0.0.0-0')]
    } else {
      sub = [new Comparator('>=0.0.0')]
    }
  }

  if (dom.length === 1 && dom[0].semver === ANY) {
    if (options.includePrerelease) {
      return true
    } else {
      dom = [new Comparator('>=0.0.0')]
    }
  }

  const eqSet = new Set()
  let gt, lt
  for (const c of sub) {
    if (c.operator === '>' || c.operator === '>=') {
      gt = higherGT(gt, c, options)
    } else if (c.operator === '<' || c.operator === '<=') {
      lt = lowerLT(lt, c, options)
    } else {
      eqSet.add(c.semver)
    }
  }

  if (eqSet.size > 1) {
    return null
  }

  let gtltComp
  if (gt && lt) {
    gtltComp = compare(gt.semver, lt.semver, options)
    if (gtltComp > 0) {
      return null
    } else if (gtltComp === 0 && (gt.operator !== '>=' || lt.operator !== '<=')) {
      return null
    }
  }

  // will iterate one or zero times
  for (const eq of eqSet) {
    if (gt && !satisfies(eq, String(gt), options)) {
      return null
    }

    if (lt && !satisfies(eq, String(lt), options)) {
      return null
    }

    for (const c of dom) {
      if (!satisfies(eq, String(c), options)) {
        return false
      }
    }

    return true
  }

  let higher, lower
  let hasDomLT, hasDomGT
  // if the subset has a prerelease, we need a comparator in the superset
  // with the same tuple and a prerelease, or it's not a subset
  let needDomLTPre = lt &&
    !options.includePrerelease &&
    lt.semver.prerelease.length ? lt.semver : false
  let needDomGTPre = gt &&
    !options.includePrerelease &&
    gt.semver.prerelease.length ? gt.semver : false
  // exception: <1.2.3-0 is the same as <1.2.3
  if (needDomLTPre && needDomLTPre.prerelease.length === 1 &&
      lt.operator === '<' && needDomLTPre.prerelease[0] === 0) {
    needDomLTPre = false
  }

  for (const c of dom) {
    hasDomGT = hasDomGT || c.operator === '>' || c.operator === '>='
    hasDomLT = hasDomLT || c.operator === '<' || c.operator === '<='
    if (gt) {
      if (needDomGTPre) {
        if (c.semver.prerelease && c.semver.prerelease.length &&
            c.semver.major === needDomGTPre.major &&
            c.semver.minor === needDomGTPre.minor &&
            c.semver.patch === needDomGTPre.patch) {
          needDomGTPre = false
        }
      }
      if (c.operator === '>' || c.operator === '>=') {
        higher = higherGT(gt, c, options)
        if (higher === c && higher !== gt) {
          return false
        }
      } else if (gt.operator === '>=' && !satisfies(gt.semver, String(c), options)) {
        return false
      }
    }
    if (lt) {
      if (needDomLTPre) {
        if (c.semver.prerelease && c.semver.prerelease.length &&
            c.semver.major === needDomLTPre.major &&
            c.semver.minor === needDomLTPre.minor &&
            c.semver.patch === needDomLTPre.patch) {
          needDomLTPre = false
        }
      }
      if (c.operator === '<' || c.operator === '<=') {
        lower = lowerLT(lt, c, options)
        if (lower === c && lower !== lt) {
          return false
        }
      } else if (lt.operator === '<=' && !satisfies(lt.semver, String(c), options)) {
        return false
      }
    }
    if (!c.operator && (lt || gt) && gtltComp !== 0) {
      return false
    }
  }

  // if there was a < or >, and nothing in the dom, then must be false
  // UNLESS it was limited by another range in the other direction.
  // Eg, >1.0.0 <1.0.1 is still a subset of <2.0.0
  if (gt && hasDomLT && !lt && gtltComp !== 0) {
    return false
  }

  if (lt && hasDomGT && !gt && gtltComp !== 0) {
    return false
  }

  // we needed a prerelease range in a specific tuple, but didn't get one
  // then this isn't a subset.  eg >=1.2.3-pre is not a subset of >=1.0.0,
  // because it includes prereleases in the 1.2.3 tuple
  if (needDomGTPre || needDomLTPre) {
    return false
  }

  return true
}
Raise error that headers already sent.

@api private