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Allow using negative index in nested list assignment #2587

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Merged
DavyLandman merged 2 commits into from
Jan 8, 2026
+12 −2
Merged

Allow using negative index in nested list assignment #2587

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4bdd971
Allow using negative index in imbricated list assignment
jbdoderlein Jan 7, 2026
68a7594
Add regression tests
jbdoderlein Jan 7, 2026
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7 changes: 7 additions & 0 deletions src/org/rascalmpl/library/lang/rascal/tests/basic/Lists.rsc
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Original file line number Diff line number Diff line change
Expand Up @@ -289,6 +289,13 @@ test bool AssignFromEnd1(){ L = [0,1,2,3,4,5,6,7,8,9]; L[-1] = 90; return L ==
test bool AssignFromEnd2(){ L = [0,1,2,3,4,5,6,7,8,9]; L[-2] = 80; return L == [0,1,2,3,4,5,6,7,80,9]; }
test bool AssignFromEnd3(){ L = [0,1,2,3,4,5,6,7,8,9]; L[-10] = 10; return L == [10,1,2,3,4,5,6,7,8,9]; }

// Nested Lists

test bool AssignNestedList1(){ L = [[0,1,2],[3,4,5],[6,7,8,9]]; L[1][2] = 50; return L == [[0,1,2],[3,4,50],[6,7,8,9]]; }
test bool AccessNestedList1(){ L = [[0,1,2],[3,4,5],[6,7,8,9]]; return L[1][2] == 5; }
test bool AssignNestedList2(){ L = [[0,1,2],[3,4,5],[6,7,8,9]]; L[-2][-1] = 50; return L == [[0,1,2],[3,4,50],[6,7,8,9]]; }
test bool AccessNestedList2(){ L = [[0,1,2],[3,4,5],[6,7,8,9]]; return L[-2][-1] == 5; }

// Library functions

test bool tstDelete(list[&T] L) {
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7 changes: 5 additions & 2 deletions src/org/rascalmpl/semantics/dynamic/Assignable.java
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Original file line number Diff line number Diff line change
Expand Up @@ -607,8 +607,11 @@ public Result<IValue> interpret(IEvaluator<Result<IValue>> __eval) {
if (receiver.getStaticType().isList()) {
if (subscript.getStaticType().isInteger()) {
IList list = (IList) receiver.getValue();
IValue result = list.get(((IInteger) subscript.getValue())
.intValue());
int index = ((IInteger) subscript.getValue()).intValue();
if (index < 0) {
index += list.length();
}
IValue result = list.get(index);
Type type = receiver.getStaticType().getElementType();
return normalizedResult(__eval, type, result);
}
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