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peter-bpeter-b
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com.livecode.list: Add "offset of _ after _ in _" accessor.
Add a new operation on lists: the offset of <tNeedle> after <tPosition> in <tList> This looks for an subsequence equal to <tNeedle> in the subsequence of <tList> starting at the 1-based index <tPosition> (exclusive). It returns the 1-based index relative to <tPosition> of the first element of the matching subsequence, or 0 if no matching subsequence is found. There are two variants of the operation: the first offset of <tNeedle> after <tPosition> in <tList> the last offset of <tNeedle> after <tPosition> in <tList> <tNeedle> must be a List.
1 parent 14a3d5a commit b0028c1

3 files changed

Lines changed: 138 additions & 1 deletion

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‎libscript/src/list.mlc‎

Lines changed: 41 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -79,6 +79,7 @@ public foreign handler MCListEvalIndexOfElementAfter(in IsLast as CBool, in Need
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public foreign handler MCListEvalIndexOfElementBefore(in IsLast as CBool, in Needle as any, in Before as LCIndex, in Haystack as List, out Index as LCUIndex) as undefined binds to "<builtin>"
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public foreign handler MCListEvalOffsetOfList(in IsLast as CBool, in Needle as List, in Haystack as List, out Index as LCUIndex) as undefined binds to "<builtin>"
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public foreign handler MCListEvalOffsetOfListAfter(in IsLast as CBool, in Needle as List, in After as LCIndex, in Haystack as List, out Index as LCUIndex) as undefined binds to "<builtin>"
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--
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@@ -991,7 +992,7 @@ Use `the offset of` to find where a particular sub-list occurs within
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a list. <Haystack> is scanned for a sequence of elements that are
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equal to the elements of <Needle>, and the position of the start of
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the sequence found is returned. If neither the "first offset" nor
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"last offset" are specified, the index of the first matching seb-list
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"last offset" are specified, the index of the first matching sub-list
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found is returned. If no sub-list of <Haystack> is equal to <Needle>,
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the return value is 0.
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@@ -1003,4 +1004,43 @@ begin
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MCListEvalOffsetOfList(IsLast, Needle, Haystack, output)
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end syntax
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/*
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Summary: Find the first or last occurrence of <Needle> within the tail of <Haystack>
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Needle: An expression which evaluates to any list.
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After: An expression which evaluates to a valid index in Target.
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Target: An expression which evaluates to a list.
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Returns: Returns the index in <Haystack> relative to <After>.
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Example:
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variable tVar as List
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variable tOffset as Number
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put ["a", "b", "c", "d", "b", "c"]
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put the offset of ["b","c"] after 1 in tVar into tOffset
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--tOffset contains 1
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put the last offset of ["b","c"] after 1 in tVar into tOffset
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--tOffset contains 4
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Description:
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Use `the offset of… after` to find where a particular sub-list occurs
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within a list. Starting from but not including the position <After>,
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<Haystack> is scanned for an sequence of elements that are equal to
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the elements of <Needle>, and the position relative to <After> of the
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start of the sequence found is returned. If neither the "first
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offset" nor "last offset" are specified, the position of the first
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matching sub-list found is returned. If no sub-list of <Haystack>
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starting after the position <After> is equal to <Needle>, the return
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value is 0.
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Tags: Lists
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*/
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syntax ListOffsetAfter is prefix operator with precedence 1
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"the" ( "first" <IsLast=false> | "last" <IsLast=true> | <IsLast=false> ) "offset" "of" <Needle: Expression> "after" <After: Expression> "in" <Haystack: Expression>
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begin
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MCListEvalOffsetOfListAfter(IsLast, Needle, After, Haystack, output)
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end syntax
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end module

‎libscript/src/module-list.cpp‎

Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -567,6 +567,28 @@ MCListEvalOffsetOfList (bool p_is_last,
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MCListEvalOffsetOfListInRange (p_is_last, p_needle, p_haystack, t_range, r_output);
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}
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extern "C" MC_DLLEXPORT void
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MCListEvalOffsetOfListAfter (bool p_is_last,
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MCProperListRef p_needle,
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index_t p_after,
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MCProperListRef p_haystack,
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uindex_t & r_output)
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{
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uindex_t t_start, t_count;
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if (!MCChunkGetExtentsOfElementChunkByExpressionInRange (p_haystack, nil,
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p_after, true, true, false, t_start, t_count) &&
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p_after != 0)
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{
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MCErrorCreateAndThrow (kMCGenericErrorTypeInfo, "reason",
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MCSTR("chunk index out of range"), nil);
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return;
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}
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MCListEvalOffsetOfListInRange (p_is_last, p_needle, p_haystack,
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MCRangeMake(t_start + t_count, UINDEX_MAX),
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r_output);
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}
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////////////////////////////////////////////////////////////////////////////////////////////////////
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#ifdef _TEST

‎tests/lcb/stdlib/list.lcb‎

Lines changed: 75 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -564,5 +564,80 @@ public handler TestOffset()
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test "offset (empty)" when the offset of [] in t is 0
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end handler
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----------------------------------------------------------------
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handler TestOffsetAfter_InvalidPositive()
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return the offset of [true] after 2 in [true]
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end handler
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handler TestOffsetAfter_InvalidNegative()
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return the offset of [true] after -3 in [true]
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end handler
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handler TestFirstOffsetAfter_InvalidPositive()
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return the first offset of [true] after 2 in [true]
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end handler
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handler TestFirstOffsetAfter_InvalidNegative()
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return the first offset of [true] after -3 in [true]
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end handler
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handler TestLastOffsetAfter_InvalidPositive()
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return the last offset of [true] after 2 in [true]
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end handler
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handler TestLastOffsetAfter_InvalidNegative()
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return the last offset of [true] after -3 in [true]
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end handler
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public handler TestOffsetAfter()
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variable t
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put [true, false, true, true, false] into t
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test "offset after (+ve)" when the offset of [true,false] after 1 in t is 3
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test "offset after (-ve)" when the offset of [true,false] after -5 in t is 3
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test "offset after (-ve, limit)" when the offset of [true,false] after -6 in t is 1
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test "offset after (+ve, missing)" when the offset of [false,true] after 2 in t is 0
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test "offset after (-ve, missing)" when the offset of [false,true] after -4 in t is 0
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MCUnitTestHandlerThrows(TestOffsetAfter_InvalidPositive, "offset after (+ve, invalid)")
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MCUnitTestHandlerThrows(TestOffsetAfter_InvalidNegative, "offset after (-ve, invalid)")
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end handler
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public handler TestFirstOffsetAfter()
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variable t
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put [true, false, true, true, false] into t
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test "first offset after (+ve)" when the first offset of [true,false] after 1 in t is 3
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test "first offset after (-ve)" when the first offset of [true,false] after -5 in t is 3
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test "first offset after (-ve, limit)" when the first offset of [true,false] after -6 in t is 1
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test "first offset after (+ve, missing)" when the first offset of [false,true] after 2 in t is 0
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test "first offset after (-ve, missing)" when the first offset of [false,true] after -4 in t is 0
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MCUnitTestHandlerThrows(TestFirstOffsetAfter_InvalidPositive, "first offset after (+ve, invalid)")
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MCUnitTestHandlerThrows(TestFirstOffsetAfter_InvalidNegative, "first offset after (-ve, invalid)")
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end handler
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public handler TestLastOffsetAfter()
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variable t
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put [true, false, true, true, false] into t
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test "last offset after (+ve)" when the last offset of [true] after 1 in t is 3
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test "last offset after (-ve)" when the last offset of [true] after -5 in t is 3
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test "last offset after (-ve, limit)" when the last offset of [true] after -6 in t is 4
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test "last offset after (+ve, missing)" when the last offset of [true] after 4 in t is 0
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test "last offset after (-ve, missing)" when the last offset of [true] after -2 in t is 0
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MCUnitTestHandlerThrows(TestLastOffsetAfter_InvalidPositive, "last offset after (+ve, invalid)")
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MCUnitTestHandlerThrows(TestLastOffsetAfter_InvalidNegative, "last offset after (-ve, invalid)")
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end handler
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public handler TestOffsetAfterZero()
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-- "offset of _ after 0 in _" should be equivalent to "offset of _ in _"
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variable t
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put [true, false, true, true, false] into t
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variable tNoAfter
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put the offset of [true,false] in t into tNoAfter
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test "offset after (+ve, 0)" when the offset of [true,false] after 0 in t is tNoAfter
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put the first offset of [true,false] in t into tNoAfter
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test "first offset after (+ve, 0)" when the first offset of [true,false] after 0 in t is tNoAfter
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put the last offset of [true,false] in t into tNoAfter
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test "last offset after (+ve, 0)" when the last offset of [true,false] after 0 in t is tNoAfter
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end handler
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end module

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