Similar to list reduce, this function takes a dictionary and reduces key-value pairs based on a reducing function. The dictionary is iterated through in order.

The function fn should be in the form def fn(acc=None, key=None, val=None). All keyword arguments are mandatory.

Arguments:

def util.dicts.reduce(
  d: dict = None, # Dictionary to reduce
  fn: function = None, # Reducing function
  default: function = None, # Default value
):

Returns the sum generated by the reduction function fn.

Example:

def red_fn(acc=0, key='', val=''):
  return acc + val
  
# 6
return util.dicts.reduce(
  d={
    'john': 1,
    'bob': 2,
    'charles': 3,
  },
  fn=red_fn,
  default=None)