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Imagine v2.0 introduces a new feature that requires a parser change—one that v1.0 wouldn't be able to parse.

  $if $defined(C3_V2_PLUS):  
      // new feature
      fn f = \ -> foo(); // this won't parse in v1.0
  $else
      Callback f = ...;
  $endif

This is also an issue if a future version of C3 introduces language level support, allowing newer compilers to compile code as if it were written for an earlier version. While this approach works well when teams standardize on a specific version’s feature set, they may still want to take advantage of performance improvements in the latest compiler.

That said, this is a niche case and not something I’d consider a dealbreaker.

sriram_malhar 17 hours ago [ - ]

You don't need an ifdef.

You just need a CLI option like java's --source, where you specify the source compatibility with different language versions.

owlstuffing 16 hours ago [ - ]

You do, that's the point here. You need ifdefs in this example to selectively compile the same code with different compilers, or different language levels with the same compiler. In either case C3 will fail while parsing a newer feature with an older compiler or lang level.

sriram_malhar 3 hours ago [ - ]

This exact situation is there in Java, using compiler args, after lambda functions were introduced. Older compilers would not be able to handle it, and the newer compilers would not break backward compatibility.

lerno 17 hours ago [ - ]

Ah, that is indeed true. However, the plan is to have the language fixed at 1.0, only updating stdlib and tooling after that.

Well, if your language gains traction that plan may not succeed. For your sake, I hope that's the case :)

lerno an hour ago [ - ]

I know it’s hard.