Lazy¶
from pymonet.lazy import Lazy
def fn():
print('fn call')
return 42
def mapper(value):
print('mapper side effect of ' + value)
return value + 1
def side_effect(value):
print('side effect of ' + value)
# Lazy instances memoize output of constructor function
lazy = Lazy(fn)
mapped_lazy = lazy.map(mapper)
mapped_lazy.fold(side_effect)
# fn call
# mapper side effect of 42
# side effect of 42
lazy = Lazy(fn)
value1 = lazy.get()
# fn call
value2 = lazy.get()
print(value1, value2)
# 42, 42
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class
pymonet.lazy.Lazy(constructor_fn: Callable[[T], U])¶ Data type for storage any type of function. This function (and all his mappers) will be called only during calling fold method
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__eq__(other: object) → bool¶ Two Lazy are equals where both are evaluated both have the same value and constructor functions.
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__init__(constructor_fn: Callable[[T], U]) → None¶ - Parameters
constructor_fn (Function() -> A) – function to call during fold method call
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bind(fn: Callable[[U], pymonet.lazy.Lazy[~ U, ~ W][U, W]]) → pymonet.lazy.Lazy[~T, ~W][T, W]¶ Take function and call constructor function passing returned value to fn function.
It’s only way to call function store in Lazy :param fn: Function(constructor_fn) -> B :returns: result od folder function :rtype: B
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get(*args)¶ Evaluate function and memoize her output or return memoized value when function was evaluated.
- Returns
result of function in Lazy
- Return type
A
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map(mapper: Callable[[U], W]) → pymonet.lazy.Lazy[~T, ~W][T, W]¶ Take function Function(A) -> B and returns new Lazy with mapped result of Lazy constructor function. Both mapper end constructor will be called only during calling fold method.
- Parameters
mapper (Function(A) -> B) – mapper function
- Returns
Lazy with mapped value
- Return type
Lazy[Function() -> B)]
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classmethod
of(value: U) → pymonet.lazy.Lazy[~T, ~U][T, U]¶ Returns Lazy with function returning argument.
- Parameters
value (Any) – value to return by Lazy constructor_fn
- Returns
Lazy with function returning argument
- Return type
Lazy[Function() -> A]
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to_validation(*args)¶ Transform Lazy into successful Validation with constructor_fn result.
- Returns
successfull Validation monad with previous value
- Return type
Validation[A, []]
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