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Fix slice() bug when index is off the end, doc fix

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Adrian Mariano
2023-01-28 11:53:02 -05:00
parent ea3e720493
commit d8dccc0005
3 changed files with 17 additions and 7 deletions
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14
lists.scad
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@@ -229,8 +229,9 @@ function select(list, start, end) =
// list = slice(list, s, e);
// Description:
// Returns a slice of a list, from the first position `s` up to and including the last position `e`.
// The first item in the list is at index 0. Negative indexes are counted back from the end.
// An index of -1 refers to the last list item.
// The first item in the list is at index 0. Negative indexes are counted back from the end, with
// -1 referring to the last list item. If `s` is after `e` then the empty list is returned.
// If an index is off the start/end of the list it will refer to the list start/end.
// Arguments:
// list = The list to get the slice of.
// start = The index of the first item to return. Default: 0
@@ -243,6 +244,8 @@ function select(list, start, end) =
// d = slice([3,4,5,6,7,8,9], 5); // Returns [8,9]
// e = slice([3,4,5,6,7,8,9], 2, -2); // Returns [5,6,7,8]
// f = slice([3,4,5,6,7,8,9], 4, 3; // Returns []
// g = slice([3,4,5], 1, 5; // Returns [4,5]
// h = slice([3,4,5], 5, 7); // Returns []
function slice(list,start=0,end=-1) =
assert(is_list(list))
assert(is_int(start))
@@ -250,11 +253,10 @@ function slice(list,start=0,end=-1) =
!list? [] :
let(
l = len(list),
start = constrain(start + (start<0? l : 0), 0, l-1),
end = constrain(end + (end<0? l : 0), 0, l-1)
start = start+(start<0 ? l : 0),
end = end + (end<0? l : 0)
)
[if (end>=start) for (i=[start:1:end]) list[i]];
[if (start<=end && end>=0 && start<=l) for (i=[max(start,0):1:min(end,l-1)]) list[i]];
// Function: last()
// Usage: