Comment by throwitaway1123

> "2 or 2000..." statement is just a jab toward mathematicians.

It's a jab towards mathematicians in the context of criticizing a language proposal. He's comparing the complexity of mathematicians and their 2000 line proofs to the complexity of allowing statements in lambdas. He explicitly calls the proposal a "Rube Goldberg contraption".

> Bit of correction: no statements and a single - arbitrarily complex - expression.

I phrased it as a dichotomy between single and multiple statements because in many languages there's the concept of an 'ExpressionStatement', which is a single expression that acts as a statement. This makes the boundaries between a single statement and an expression somewhat murky. In JS for example the MDN docs have this to say about ExpressionStatements: "Apart from the dedicated statement syntaxes, you can also use almost any expression as a statement on its own." [1] GVR himself calls it "the problem of the multi-statement lambda" rather than "the problem of the statement lambda".

I don't want to get bogged down in pedantic debates about terminology though. I completely understand how it works, and said in my very first reply to you: "but it's nice to not be limited to expressions".

> End of the day, support for statements in a lambda would lead to a need for new symbols.

All it would require is a newline character. He calls this out in the blog post: "If the double colon is unpythonic, perhaps a solution could be found that uses a single colon and is still backwards compatible [...] I actually have one in mind: if there's text after the colon, it's a backwards-compatible expression lambda; if there's a newline, it's a multi-line lambda; the rest of the proposal can remain unchanged. Presto, QED, voila, etcetera."

There's absolutely nothing complex about allowing statements in lambdas from a user interface perspective (all of the complexity is in the implementation). Almost every modern language has support for this feature. Even Golang, which is perhaps the epitome of simplicity — the language that fought tooth and nail against generics, and doesn't have a ternary operator (or inline if), or string interpolation — supports defining inline callback functions with statements. There are even whitespace sensitive languages like CoffeeScript that bit the bullet and don't impose any restrictions on lambdas. The simplicity argument just feels really weak to me. At the time that blog post was written a Python user couldn't add a print statement to a lambda to debug their code. How in the world is that simple for biology students and people writing one-off projects?

[1] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...