Re: Block lambda is cool, its syntax isn't

Thu, 12 Jan 2012 22:58:51 -0800

January 12, 2012 10:23 PM


Two more pro-pipe points: block lambdas (lambda blocks?) will often be arguments of functions:
foo( {|x,y| x + y } )
foo( {(x,y) x + y } )

With parens, you are starting to look a bit like Lisp... ;-)

Agreed, although note that you can go paren-free in the call:

  foo {|x,y| x+y}

But there will be paren-ful call cases.

I also find that pipes stick out better as something alien. Parens feel too much like someone has forgotten to add a semicolon, inside a normal block:
https://gist.github.com/d2c8fcbab5a3da4c4dae (Rick Waldron’s Gist comparing parens and pipes)

Yup.

But man does that code profit from block lambdas – really nice to look at. In some cases, things would fit into a single line where you were forced to split into multiple lines without BLs.

It's not just the line savings -- the lack of 'function' deadwood  and 'return' just to have a result value win too. (I didn't see any TCP-based control effects.)

/be

January 12, 2012 7:33 PM
The correspondence principle is a big change for the body, so even if we could reserve block or abuse do, making the special form look like function (params) { body } is a mistake. 'return' does not return from the block, it returns from the enclosing function.

I'm not in love with Ruby syntax but {(a, b) a + b} isn't as distinctive and clearly a lambda-like thing. You're right about that, but turning back to function-based syntax with a different introductory keyword goes the wrong direction. This is why I keep coming back to "different syntax is a virtue". The correspondence-principle-based semantics are different enough.

/be

January 12, 2012 5:44 PM

I agree. While Ruby and Smalltalk are useful to continue mining for
ideas, they shouldn't be a source of syntax, as they're not
super-popular. Using || to denote an argument list looks *bizarre* to
my eyes, and I suspect also to the eyes of every single person who's
used a C-like language but not Ruby.

I'm not wedded to {(a,b) a + b} for blocks either, but it's at least
an improvement over {|a,b| a + b}. I wouldn't mind something simple
like "block(a,b){a+b}" or even "do(a,b){a+b}", though those probably
run into ambiguity issues.

~TJ
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