[treeplayer] Fix Alt$(array) to iterate correctly when used standalone#22599
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guitargeek wants to merge 1 commit into
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[treeplayer] Fix Alt$(array) to iterate correctly when used standalone#22599guitargeek wants to merge 1 commit into
Alt$(array) to iterate correctly when used standalone#22599guitargeek wants to merge 1 commit into
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A standalone Alt$ on a variable-length array, e.g.
```c++
t.Scan("Alt$(x,-1)");
```
only ever evaluated the first element of each entry instead of looping
over the whole array. The combined form `x:Alt$(x,-1)` worked because
the sibling formula `x` drove the iteration, which made the bug easy to
miss.
Root cause: `TTreeFormula::ResetDimensions()` never accounted for the
`kAlternate`/`kAlternateString` actions when computing `fMultiplicity`.
By design, `Alt$` hides its primary operand from the TTreeFormulaManager
so that, in expressions like `arr1+Alt$(arr2,0)`, `arr1` drives the loop
and the alternate pads the entries where `arr2` is too short. But when
`Alt$` is the *only* source of multiplicity there is no sibling to drive
the loop, so the formula collapsed to a single instance.
Fix: in `ResetDimensions()`, after the main operand loop, if the formula
has no other multiplicity (`fMultiplicity == 0`) scan for `kAlternate`/
`kAlternateString` operands and register their primary with the manager
when that primary is itself a genuine array.
Adds two regression tests: **AltDollarVariableArray** (standalone `Alt$`
now loops; `Alt$(x[2],-1)` keeps its fall-back behaviour) and
**AltDollarPadsShorterArray** (the documented `arr1+Alt$(arr2,0)`
padding still iterates over the longer array).
Closes root-project#6378.
🤖 Done with the help of [Claude Code](https://claude.com/claude-code) (Claude Opus 4.8)
guitargeek
changed the title
Alt$(array) to iterate correctly when used standalone
Test Results 21 files 21 suites 3d 7h 40m 3s ⏱️ Results for commit 40c7101. ♻️ This comment has been updated with latest results. |
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A standalone Alt$ on a variable-length array, e.g.
t.Scan("Alt$(x,-1)");only ever evaluated the first element of each entry instead of looping over the whole array. The combined form
x:Alt$(x,-1)worked because the sibling formulaxdrove the iteration, which made the bug easy to miss.Root cause:
TTreeFormula::ResetDimensions()never accounted for thekAlternate/kAlternateStringactions when computingfMultiplicity. By design,Alt$hides its primary operand from the TTreeFormulaManager so that, in expressions likearr1+Alt$(arr2,0),arr1drives the loop and the alternate pads the entries wherearr2is too short. But whenAlt$is the only source of multiplicity there is no sibling to drive the loop, so the formula collapsed to a single instance.Fix: in
ResetDimensions(), after the main operand loop, if the formula has no other multiplicity (fMultiplicity == 0) scan forkAlternate/kAlternateStringoperands and register their primary with the manager when that primary is itself a genuine array.Adds two regression tests: AltDollarVariableArray (standalone
Alt$now loops;Alt$(x[2],-1)keeps its fall-back behaviour) and AltDollarPadsShorterArray (the documentedarr1+Alt$(arr2,0)padding still iterates over the longer array).Closes #6378.
🤖 Done with the help of Claude Code (Claude Opus 4.8)