Struct, sig, do ... -> begin?

Learning
1

We have various syntactic structures that contain blocks of code, eg:

for ... do
end

module M = struct
end

module type MT = sig
end

We also have begin...end which seems to be a synonym for (...).

Is there some reason why we can’t use begin for all of the above blocks, or is it purely for historical reasons?

2
  1. You’d need to change the parser; it’s not backwards compatible.
  2. struct and sig can stand by themselves, without assignment. How would you indicate that you mean one or the other if you just use begin?
3

agreed, it’s no use if we just keep the two syntax side by side anyway.

you know from context when you’re in a module or module type context, so that’s not a problem, I think. module A = <module context here>, module type FOO = <module type context here>, open <module context here>, etc.

4

Just historical/tradition reasons. Technically there is no problem: ReasonML used { and } to delineate all blocks.

Cheers,
Nicolas