mathext.lua

function math.isinf(x)
  argcheck(x,1,'number')
  
  return (
    x ==  math.huge and  1 or
    x == -math.huge and -1
  )
end

function math.isnan(x)
  argcheck(x,1,'number')
  
  return x ~= x
end

function math.finite(x)
  argcheck(x,1,'number')
  
  return (
    x > -math.huge and
    x <  math.huge
  )
end