incVars initialLevel j = assert (j > 0) $ instantiateVars fn initialLevel
  where fn _ i = Term $ LocalVar (i+j)

-- | Substitute @ts@ for variables @[k .. k + length ts - 1]@ and
-- decrement all higher loose variables by @length ts@.
incVars initialLevel j = assert (j > 0) $ instantiateVars fn initialLevel
  where fn _ i = Term $ LocalVar (i+j)

-- | Substitute @ts@ for variables @[k .. k + length ts - 1]@ and
-- decrement all higher loose variables by @length ts@.
incVars initialLevel j = assert (j > 0) $ instantiateVars fn initialLevel
  where fn _ i = Term $ LocalVar (i+j)

-- | Substitute @ts@ for variables @[k .. k + length ts - 1]@ and
-- decrement all higher loose variables by @length ts@.