Implementation-wise, it's no so difficult to include - the lexer needs to be tweaked. But it seems like a specialised use-case that will only affect a minority of users is probably not worthwhile as an extension to the language/compiler.

Maybe you can try using OverloadedStrings and implement this as a library?

```

newtype Binary = Binary Integer

  deriving Num

instance IsString Binary where

  fromString binaryLiteral = error "Code here to parse binary literal with underscores"

binaryVal :: Binary

binaryVal = "1101_1110_0101"

```

Hope that helps,

Rahul

On Tue, Sep 26, 2017 at 8:40 AM, Takenobu Tani <takenobu.hs@gmail.com> wrote:

Dear devs,

GHC's BinaryLiterals extension is useful.
(For example, x = 0b110111000101)

Is it difficult to include underscore(_) in the format like Verilog-HDL[1] ?
(For example, x = 0b1101_1100_0101)

[1]: https://inst.eecs.berkeley.edu/~cs150/fa06/Labs/verilog-ieee.pdf#page=20

Regards,
Takenobu

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Rahul Muttineni