Champion "Binary Literals" and "Digit Separators" (C# 7.0)

[gafter]

• [x] Proposal added (binary literals, digit separators)
• [x] Discussed in LDM (2016-10-18)
• [x] Decision in LDM
• [x] Finalized (done, rejected, inactive)
• [ ] Spec'ed

See also

• https://github.com/dotnet/roslyn/issues/215
• https://github.com/dotnet/roslyn/issues/216

[gafter]

This is a "proposal issue" because we need to add a proposal/spec to the repo.

[Alexhuszagh]

Is there any particular reason why digit separators are allowed in integer digits, but not in fraction digits? For example:

> 1_2;             // "Works" (weirdly), 122
> 1_2.34;       // "Works" (wierdly), 122.34
> 122.3_4;     // Fails, (1,6): error CS1525: Unexpected symbol `_4'

System Information (running Mono on Fedora 30):

$ mono --version
Mono JIT compiler version 6.8.0.96 (tarball Wed Jan 15 09:00:57 UTC 2020)
Copyright (C) 2002-2014 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
	TLS:           __thread
	SIGSEGV:       altstack
	Notifications: epoll
	Architecture:  amd64
	Disabled:      none
	Misc:          softdebug 
	Interpreter:   yes
	LLVM:          yes(610)
	Suspend:       hybrid
	GC:            sgen (concurrent by default)

Command To Start Interpreter:

csharp -langversion:Experimental

[CyrusNajmabadi]

Is there any particular reason why digit separators are allowed in integer digits, but not in fraction digits?

It is allowed.

Fails, (1,6): error CS1525: Unexpected symbol `_4' System Information (running Mono on Fedora 30):

Sounds like a mono problem. Maybe report this to them?

[gafter]

Specification in progress at https://github.com/dotnet/csharpstandard/pull/548.