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com.livecode.list: Add "index of _ after _ in _" accessor.
Add a new operation on lists: the index of <tNeedle> after <tPosition> in <tList> This looks for an element 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>, or 0 if no element of of the subsequence is equal to <tNeedle>. There are two variants of the operation: the first index of <tNeedle> after <tPosition> in <tList> the last index of <tNeedle> after <tPosition> in <tList> If <tNeedle> is a list, it is considered as an element of <tList> not as a subsequence of <tList>.
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‎libscript/src/list.mlc‎

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@@ -75,6 +75,7 @@ public foreign handler MCListExecDeleteFirstElementOf(inout Target as List) as u
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public foreign handler MCListExecDeleteLastElementOf(inout Target as List) as undefined binds to "<builtin>"
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public foreign handler MCListEvalIndexOfElement(in IsLast as CBool, in Needle as any, in Haystack as List, out Index as LCUIndex) as undefined binds to "<builtin>"
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public foreign handler MCListEvalIndexOfElementAfter(in IsLast as CBool, in Needle as any, 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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@@ -893,4 +894,38 @@ begin
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MCListEvalIndexOfElement(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 value.
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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"]
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put the index of "b" after 1 in tVar into tOffset
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--tOffset contains 1
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put the last index of "b" after 2 in tVar into tOffset
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--tOffset contains 3
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Description:
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Use `the index of… after` to find where particular elements occur
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within a list. Starting from but not including the position <After>,
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<Haystack> is scanned for an element that is equal to <Needle>, and
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the position relative to <After> of the element found is returned. If
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no element of <Haystack> is equal to <Needle>, the return value is 0.
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Tags: Lists
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*/
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syntax ListIndexAfter is prefix operator with precedence 1
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"the" ( "first" <IsLast=false> | "last" <IsLast=true> | <IsLast=false> ) "index" "of" <Needle: Expression> "after" <After: Expression> "in" <Haystack: Expression>
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begin
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MCListEvalIndexOfElementAfter(IsLast, Needle, After, Haystack, output)
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end syntax
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end module

‎libscript/src/module-list.cpp‎

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@@ -481,6 +481,28 @@ MCListEvalIndexOfElement (bool p_is_last,
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MCListEvalIndexOfElementInRange (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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MCListEvalIndexOfElementAfter (bool p_is_last,
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MCValueRef 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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MCListEvalIndexOfElementInRange (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

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@@ -392,4 +392,77 @@ public handler TestIndex()
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test "index (empty)" when the index of 1 in [] is 0
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end handler
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handler TestIndexAfter_InvalidPositive()
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return the index of true after 2 in [true]
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end handler
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handler TestIndexAfter_InvalidNegative()
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return the index of true after -3 in [true]
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end handler
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handler TestFirstIndexAfter_InvalidPositive()
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return the first index of true after 2 in [true]
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end handler
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handler TestFirstIndexAfter_InvalidNegative()
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return the first index of true after -3 in [true]
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end handler
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handler TestLastIndexAfter_InvalidPositive()
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return the last index of true after 2 in [true]
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end handler
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handler TestLastIndexAfter_InvalidNegative()
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return the last index of true after -3 in [true]
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end handler
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public handler TestIndexAfter()
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variable t
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put [true, false, true, true, false] into t
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test "index after (+ve)" when the index of true after 1 in t is 2
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test "index after (-ve)" when the index of true after -5 in t is 2
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test "index after (-ve, limit)" when the index of true after -6 in t is 1
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test "index after (+ve, missing)" when the index of true after 4 in t is 0
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test "index after (-ve, missing)" when the index of true after -2 in t is 0
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MCUnitTestHandlerThrows(TestIndexAfter_InvalidPositive, "index after (+ve, invalid)")
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MCUnitTestHandlerThrows(TestIndexAfter_InvalidNegative, "index after (-ve, invalid)")
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end handler
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public handler TestFirstIndexAfter()
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variable t
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put [true, false, true, true, false] into t
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test "first index after (+ve)" when the first index of true after 1 in t is 2
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test "first index after (-ve)" when the first index of true after -5 in t is 2
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test "first index after (-ve, limit)" when the first index of true after -6 in t is 1
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test "first index after (+ve, missing)" when the first index of true after 4 in t is 0
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test "first index after (-ve, missing)" when the first index of true after -2 in t is 0
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MCUnitTestHandlerThrows(TestFirstIndexAfter_InvalidPositive, "first index after (+ve, invalid)")
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MCUnitTestHandlerThrows(TestFirstIndexAfter_InvalidNegative, "first index after (-ve, invalid)")
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end handler
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public handler TestLastIndexAfter()
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variable t
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put [true, false, true, true, false] into t
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test "last index after (+ve)" when the last index of true after 1 in t is 3
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test "last index after (-ve)" when the last index of true after -5 in t is 3
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test "last index after (-ve, limit)" when the last index of true after -6 in t is 4
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test "last index after (+ve, missing)" when the last index of true after 4 in t is 0
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test "last index after (-ve, missing)" when the last index of true after -2 in t is 0
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MCUnitTestHandlerThrows(TestLastIndexAfter_InvalidPositive, "last index after (+ve, invalid)")
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MCUnitTestHandlerThrows(TestLastIndexAfter_InvalidNegative, "last index after (-ve, invalid)")
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end handler
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public handler TestIndexAfterZero()
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-- "index of _ after 0 in _" should be equivalent to "index 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 index of true in t into tNoAfter
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test "index after (+ve, 0)" when the index of true after 0 in t is tNoAfter
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put the first index of true in t into tNoAfter
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test "first index after (+ve, 0)" when the first index of true after 0 in t is tNoAfter
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put the last index of true in t into tNoAfter
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test "last index after (+ve, 0)" when the last index of true after 0 in t is tNoAfter
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end handler
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end module

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