Feature Request: Allow Underscore in Numeric Literals Again

[macdjord]

YAML 1.1 allowed numeric literals, i.e. ints and floats, to include underscores, which were semantically ignored. They could thus be used for digit grouping in long values, much as commas are often used as thousands-separators in human-readable text. This was very convenient, and greatly improved readability for large values.

YAML 1.2.0 dropped this feature, for no reason I can find documented anywhere.

I propose that YAML 1.3 bring this feature back.

[KJTsanaktsidis]

I believe the reason is so that the regular expressions for implicit resolution of !int and !float match the JSON rules, since the aim of YAML 1.2 was to be a strict superset of JSON.