Researcher question – what's the point of semicolons and curly braces?

[Joe Duarte via Digitalmars-d]

Hi all,

I'm a social scientist and I'm preparing some studies on the 
effects of programming language syntax on learning, motivation to 
pursue programming, as well as any disproportionate effects that 
PL syntax has on the appeal of programming to women (more on the 
latter in a separate post).

So I want to get a better idea of the rationale for various 
syntactical design decisions, and I'm going to ask you the same 
question I'll ask the Rust community:

Why are curly braces and semicolons necessary? What information 
do they carry that a compiler could not otherwise reliably obtain?

Here's an example from the D Overview page:


class Foo
{
     int foo(Bar c) { return c.bar; }
}

class Bar
{
     int bar() { return 3; }
}


Okay, if we remove the curly braces and semicolons, we have:


class Foo

     int foo(Bar c) return c.bar


class Bar

     int bar() return 3


Would it be difficult to compile the clean version? Would there 
be issues with the design of the lexer/parser? I assume the 
compiler would recognize keywords like return (and a clean syntax 
could drive different rules for what statements and expressions 
could appear on the same line and so forth).

In reality, a compiler would see the above with line ending 
characters terminating every line (e.g. U+000A), so it would be 
as line-aware as a human. I've never built lexers or parsers, 
much less compilers, so maybe I'm missing a major implementation 
hurdle. I'm just thinking that Facebook has built software that 
recognizes my face in other people's pictures, so it seems like 
building software that understands structured text would be a 
solved problem. It puzzles me to see so much apparent punctuation 
noise in a 21st-century language (and, to be fair, Rust puzzles 
me for the same reasons).

JD