[ruby-core:124474] [Ruby Bug#21831] Prism doesn't count underscores in the fraction part of rational float

11 Jan 2026


      Issue #21831 has been reported by nobu (Nobuyoshi Nakada).

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Bug #21831: Prism doesn't count underscores in the fraction part of rational float
https://bugs.ruby-lang.org/issues/21831

* Author: nobu (Nobuyoshi Nakada)
* Status: Open
* Backport: 3.2: REQUIRED, 3.3: REQUIRED, 3.4: REQUIRED, 4.0: REQUIRED
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Good.
```console
$ ruby3.3 -e 'p 0.1_2r.to_f'
0.12

$ ruby3.4 --parser=parse.y -e 'p 0.1_2r.to_f'
0.12
```

Wrong.
```console
$ ruby3.4 -e 'p 0.1_2r.to_f'
0.012
```


-- 
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