# -*- coding: utf-8 -*-

"""Operations on sequences, with native slice syntax. Syntactic sugar, pure Python."""

from ..syntax import macros, test, test_raises # noqa: F401

from ..test.fixtures import session, testset

from itertools import repeat

from ..slicing import fup, islice

from ..mathseq import primes, s

def runtests():

# functional update for sequences

# (when you want to be more functional than Python allows)

with testset("slice syntax for fupdate"):

tup = (1, 2, 3, 4, 5)

test[type(fup(tup)[3] << 42) is type(tup)]

test[fup(tup)[3] << 42 == (1, 2, 3, 42, 5)]

test[fup(tup)[0::2] << tuple(repeat(10, 3)) == (10, 2, 10, 4, 10)]

test[fup(tup)[1::2] << tuple(repeat(10, 3)) == (1, 10, 3, 10, 5)]

test[fup(tup)[::2] << tuple(repeat(10, 3)) == (10, 2, 10, 4, 10)]

test[fup(tup)[::-1] << tuple(range(5)) == (4, 3, 2, 1, 0)]

test[tup == (1, 2, 3, 4, 5)]

test_raises[TypeError, fup(tup)[2, 3]] # multidimensional indexing not supported

with testset("slice syntax wrapper for itertools.islice"):

p = primes()

test[tuple(islice(p)[10:15]) == (31, 37, 41, 43, 47)]

test[tuple(islice(primes())[10:15]) == (31, 37, 41, 43, 47)]

p = primes()

test[islice(p)[10] == 31]

odds = islice(s(1, 2, ...))[::2]

test[tuple(islice(odds)[:5]) == (1, 3, 5, 7, 9)]

test[tuple(islice(odds)[:5]) == (11, 13, 15, 17, 19)] # five more

finite = (x for x in range(5)) # consumable iterable, no sequence protocol

test[islice(finite)[-1] == 4]

with testset("negative start, stop in the islice wrapper"):

# !! step must be positive !!

#

# CAUTION: will force the iterable (at the latest at the time when the

# first item is read from it), since that's the only way to know where it

# ends, if at all.

test[tuple(islice(range(10))[-3:]) == (7, 8, 9)] # start < 0, no stop

test[tuple(islice(range(10))[-3:9]) == (7, 8)] # start < 0, stop > 0, before end

test[tuple(islice(range(10))[-2:10]) == (8, 9)] # start < 0, stop > 0, at end

test[tuple(islice(range(10))[-2:20]) == (8, 9)] # start < 0, stop > 0, beyond end

test[tuple(islice(range(10))[:-8]) == (0, 1)] # no start, stop < 0

test[tuple(islice(range(10))[6:-2]) == (6, 7)] # start > 0, stop < 0

test[tuple(islice(range(10))[10:-2]) == ()] # start > 0, at end, stop < 0

test[tuple(islice(range(10))[20:-2]) == ()] # start > 0, beyond end, stop < 0

test[tuple(islice(range(10))[-8:-4]) == (2, 3, 4, 5)] # start < 0, stop < 0

test[tuple(islice(range(10))[-6::2]) == (4, 6, 8)] # step

test[tuple(islice(range(10))[:-2:2]) == (0, 2, 4, 6)] # step

test[tuple(islice(range(10))[-8:-2:3]) == (2, 5)] # step

# edge cases, should behave like list does

test[tuple(islice(range(10))[:-20]) == ()] # stop < 0, past the start of the iterable

test[tuple(islice(range(10))[-20:]) == tuple(range(10))] # start < 0, past the start of the iterable

test[tuple(islice(range(10))[-20:5]) == tuple(range(5))] # same, but with stop > 0

with testset("error cases"):

test_raises[TypeError, islice(range(10))[2, 3]] # multidimensional indexing not supported

if __name__ == '__main__': # pragma: no cover

with session(__file__):

runtests()