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py: Support __len__ of rangetype. by corona10 · Pull Request #40 · go-python/gpython · GitHub

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py: Support __len__ of rangetype. #40

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Merged
ncw merged 1 commit into from
Dec 26, 2018
Conversation 3 Commits 1 Checks 0 Files changed
Merged

py: Support __len__ of rangetype. #40

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47 changes: 37 additions & 10 deletions py/range.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,10 +9,10 @@ package py
// A python Range object
// FIXME one day support BigInts too!
type Range struct {
Start Int
Stop Int
Step Int
//Length Object
Start Int
Stop Int
Step Int
Length Int
}

// A python Range iterator
Expand Down Expand Up @@ -53,10 +53,12 @@ func RangeNew(metatype *Type, args Tuple, kwargs StringDict) (Object, error) {
return nil, err
}
if len(args) == 1 {
length := computeRangeLength(0, startIndex, 1)
return &Range{
Start: Int(0),
Stop: startIndex,
Step: Int(1),
Start: Int(0),
Stop: startIndex,
Step: Int(1),
Length: length,
}, nil
}
stopIndex, err := Index(stop)
Expand All @@ -67,10 +69,12 @@ func RangeNew(metatype *Type, args Tuple, kwargs StringDict) (Object, error) {
if err != nil {
return nil, err
}
length := computeRangeLength(startIndex, stopIndex, stepIndex)
return &Range{
Start: startIndex,
Stop: stopIndex,
Step: stepIndex,
Start: startIndex,
Stop: stopIndex,
Step: stepIndex,
Length: length,
}, nil
}

Expand All @@ -82,6 +86,10 @@ func (r *Range) M__iter__() (Object, error) {
}, nil
}

func (r *Range) M__len__() (Object, error) {
return r.Length, nil
}

// Range iterator
func (it *RangeIterator) M__iter__() (Object, error) {
return it, nil
Expand All @@ -97,6 +105,25 @@ func (it *RangeIterator) M__next__() (Object, error) {
return r, nil
}

func computeRangeLength(start, stop, step Int) Int {
var lo, hi Int
if step > 0 {
lo = start
hi = stop
step = step
} else {
lo = stop
hi = start
step = (-step)
}

if lo >= hi {
return Int(0)
}
res := (hi-lo-1)/step + 1
return res
}

// Check interface is satisfied
var _ I__iter__ = (*Range)(nil)
var _ I_iterator = (*RangeIterator)(nil)
16 changes: 16 additions & 0 deletions py/tests/range.py
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@@ -0,0 +1,16 @@
# Copyright 2018 The go-python Authors. All rights reserved.
# Use of this source code is governed by a BSD-style
# license that can be found in the LICENSE file.

doc="range"
a = range(255)
b = [e for e in a]
assert len(a) == len(b)
a = range(5, 100, 5)
b = [e for e in a]
assert len(a) == len(b)
a = range(100 ,0, 1)
b = [e for e in a]
assert len(a) == len(b)

doc="finished"
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