python PS

ps.py

# (v -> Boolean) -> Boolean

class State:
  pass

def empty():
  return lambda r: True

def singleton(v):
  return lambda r: r(v)

def where(f, ps):
  return lambda r: ps(lambda v: r(v) if f(v) else True)

def select(m, ps):
  return lambda r: ps(lambda v: r(m(v)))

def collect(m, ps):
  return lambda r: ps(lambda v: m(v)(r))

def debug(nm, ps):
  def dps(r):
    def dr(v):
      res = r(v)
      print("DEBUG - %s - %s - %s" % (nm, res, v))
      return res
    ps(dr)
  return dps

def fromList(vs):
  def ps(r):
    for v in vs:
      if not r(v):
        return False
    return True
  return ps

def fold(f, z, ps):
  st = State()
  st.acc = z
  def r(v):
    st.acc = f(st.acc, v)
    return True
  ps(r)
  return st.acc

def toList(ps):
  acc = []
  ps(lambda v: acc.append(v) or True)
  return acc

def first(ps):
  st = State()
  st.acc = None
  def r(v):
    st.acc = v
    return False
  ps(r)
  return st.acc

toList(where(lambda v: v > 2, select(lambda v: v + 1, fromList([1,2,3]))))