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Merged
merged 2 commits into from
Nov 22, 2019
Merged

Add itertools.combinations() #1603

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dralley Nov 17, 2019
16b2b42
Add itertools.combinations()
dralley Nov 21, 2019
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23 changes: 23 additions & 0 deletions tests/snippets/stdlib_itertools.py
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Original file line number Diff line number Diff line change
Expand Up @@ -301,6 +301,7 @@ def assert_matches_seq(it, seq):
assert list(t[0]) == []

# itertools.product

it = itertools.product([1, 2], [3, 4])
assert (1, 3) == next(it)
assert (1, 4) == next(it)
Expand All @@ -321,3 +322,25 @@ def assert_matches_seq(it, seq):
itertools.product(None)
with assert_raises(TypeError):
itertools.product([1, 2], repeat=None)

# itertools.combinations

it = itertools.combinations([1, 2, 3, 4], 2)
assert list(it) == [(1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]

it = itertools.combinations([1, 2, 3], 1)
assert list(it) == [(1,), (2,), (3,)]

it = itertools.combinations([1, 2, 3], 2)
assert next(it) == (1, 2)
assert next(it) == (1, 3)
assert next(it) == (2, 3)
with assert_raises(StopIteration):
next(it)

it = itertools.combinations([1, 2, 3], 4)
with assert_raises(StopIteration):
next(it)

with assert_raises(ValueError):
itertools.combinations([1, 2, 3, 4], -2)
144 changes: 127 additions & 17 deletions vm/src/stdlib/itertools.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ use std::ops::{AddAssign, SubAssign};
use std::rc::Rc;

use num_bigint::BigInt;
use num_traits::sign::Signed;
use num_traits::ToPrimitive;

use crate::function::{Args, OptionalArg, PyFuncArgs};
Expand Down Expand Up @@ -733,14 +734,14 @@ impl PyItertoolsTee {

#[pyclass]
#[derive(Debug)]
struct PyIterToolsProduct {
struct PyItertoolsProduct {
pools: Vec<Vec<PyObjectRef>>,
idxs: RefCell<Vec<usize>>,
cur: Cell<usize>,
stop: Cell<bool>,
}

impl PyValue for PyIterToolsProduct {
impl PyValue for PyItertoolsProduct {
fn class(vm: &VirtualMachine) -> PyClassRef {
vm.class("itertools", "product")
}
Expand All @@ -753,7 +754,7 @@ struct ProductArgs {
}

#[pyimpl]
impl PyIterToolsProduct {
impl PyItertoolsProduct {
#[pyslot(new)]
fn tp_new(
cls: PyClassRef,
Expand All @@ -780,7 +781,7 @@ impl PyIterToolsProduct {

let l = pools.len();

PyIterToolsProduct {
PyItertoolsProduct {
pools,
idxs: RefCell::new(vec![0; l]),
cur: Cell::new(l - 1),
Expand Down Expand Up @@ -848,19 +849,137 @@ impl PyIterToolsProduct {
}
}

#[pyclass]
#[derive(Debug)]
struct PyItertoolsCombinations {
pool: Vec<PyObjectRef>,
indices: RefCell<Vec<usize>>,
r: Cell<usize>,
exhausted: Cell<bool>,
}

impl PyValue for PyItertoolsCombinations {
fn class(vm: &VirtualMachine) -> PyClassRef {
vm.class("itertools", "combinations")
}
}

#[pyimpl]
impl PyItertoolsCombinations {
#[pyslot(new)]
fn tp_new(
cls: PyClassRef,
iterable: PyObjectRef,
r: PyIntRef,
vm: &VirtualMachine,
) -> PyResult<PyRef<Self>> {
let iter = get_iter(vm, &iterable)?;
let pool = get_all(vm, &iter)?;

let r = r.as_bigint();
if r.is_negative() {
return Err(vm.new_value_error("r must be non-negative".to_string()));
}
let r = r.to_usize().unwrap();

let n = pool.len();

PyItertoolsCombinations {
pool,
indices: RefCell::new((0..r).collect()),
r: Cell::new(r),
exhausted: Cell::new(r > n),
}
.into_ref_with_type(vm, cls)
}

#[pymethod(name = "__iter__")]
fn iter(zelf: PyRef<Self>, _vm: &VirtualMachine) -> PyRef<Self> {
zelf
}

#[pymethod(name = "__next__")]
fn next(&self, vm: &VirtualMachine) -> PyResult {
// stop signal
if self.exhausted.get() {
return Err(new_stop_iteration(vm));
}

let n = self.pool.len();
let r = self.r.get();

let res = PyTuple::from(
self.pool
.iter()
.enumerate()
.filter(|(idx, _)| self.indices.borrow().contains(&idx))
.map(|(_, num)| num.clone())
.collect::<Vec<PyObjectRef>>(),
);

let mut indices = self.indices.borrow_mut();
let mut sentinel = false;

// Scan indices right-to-left until finding one that is not at its maximum (i + n - r).
let mut idx = r - 1;
loop {
if indices[idx] != idx + n - r {
sentinel = true;
break;
}

if idx != 0 {
idx -= 1;
} else {
break;
}
}
// If no suitable index is found, then the indices are all at
// their maximum value and we're done.
if !sentinel {
self.exhausted.set(true);
}

// Increment the current index which we know is not at its
// maximum. Then move back to the right setting each index
// to its lowest possible value (one higher than the index
// to its left -- this maintains the sort order invariant).
indices[idx] += 1;
for j in idx + 1..r {
indices[j] = indices[j - 1] + 1;
}

Ok(res.into_ref(vm).into_object())
}
}

pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
let ctx = &vm.ctx;

let accumulate = ctx.new_class("accumulate", ctx.object());
PyItertoolsAccumulate::extend_class(ctx, &accumulate);

let chain = PyItertoolsChain::make_class(ctx);

let compress = PyItertoolsCompress::make_class(ctx);

let combinations = ctx.new_class("combinations", ctx.object());
PyItertoolsCombinations::extend_class(ctx, &combinations);

let count = ctx.new_class("count", ctx.object());
PyItertoolsCount::extend_class(ctx, &count);

let dropwhile = ctx.new_class("dropwhile", ctx.object());
PyItertoolsDropwhile::extend_class(ctx, &dropwhile);

let islice = PyItertoolsIslice::make_class(ctx);

let filterfalse = ctx.new_class("filterfalse", ctx.object());
PyItertoolsFilterFalse::extend_class(ctx, &filterfalse);

let product = ctx.new_class("product", ctx.object());
PyItertoolsProduct::extend_class(ctx, &product);

let repeat = ctx.new_class("repeat", ctx.object());
PyItertoolsRepeat::extend_class(ctx, &repeat);

Expand All @@ -869,30 +988,21 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
let takewhile = ctx.new_class("takewhile", ctx.object());
PyItertoolsTakewhile::extend_class(ctx, &takewhile);

let islice = PyItertoolsIslice::make_class(ctx);

let filterfalse = ctx.new_class("filterfalse", ctx.object());
PyItertoolsFilterFalse::extend_class(ctx, &filterfalse);

let accumulate = ctx.new_class("accumulate", ctx.object());
PyItertoolsAccumulate::extend_class(ctx, &accumulate);

let tee = ctx.new_class("tee", ctx.object());
PyItertoolsTee::extend_class(ctx, &tee);
let product = ctx.new_class("product", ctx.object());
PyIterToolsProduct::extend_class(ctx, &product);

py_module!(vm, "itertools", {
"accumulate" => accumulate,
"chain" => chain,
"compress" => compress,
"combinations" => combinations,
"count" => count,
"dropwhile" => dropwhile,
"islice" => islice,
"filterfalse" => filterfalse,
"repeat" => repeat,
"starmap" => starmap,
"takewhile" => takewhile,
"islice" => islice,
"filterfalse" => filterfalse,
"accumulate" => accumulate,
"tee" => tee,
"product" => product,
})
Expand Down