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Ah OK, that makes sense. So Python doesn't have that issue because it doesn't overload braces for hashes and blocks. Oil does overload them, but it has a sepa

by chubot 7y ago

Ah OK, that makes sense. So Python doesn't have that issue because it doesn't overload braces for hashes and blocks. Oil does overload them, but it has a separate lexing mode for statements and expressions. It switches when it sees say the 'var' keyword, so the right of var x = {a: 3} is lexed as an expression rather than a statement. This sort of fell out of compatibility constraints with shell, but ended up being pretty convenient and powerful. The lexing mode relies pretty strongly on having the "first word", e.g. 'var' or 'func', Pascal-style. So yeah I can see how it would be more complex with Java-style syntax.

munificent 7y ago
> So Python doesn't have that issue because it doesn't overload braces for hashes and blocks. Yes, and also because lambdas in Python can only have expression bodies, not statements. That means you can never have a statement nested inside an expression. This is important because Python's rule to ignore all newlines between parentheses would fall apart if you could stuff a statement-bodied function inside a parenthesized expression.
- chubot 7y ago
  Yes the lambda issue is something I ran into for Oil. Although this part of the language is deferred, the parser is implemented: # Ruby/Rust style lambda, with the Python constraint that the body can only be an expression var inc = |x| x + 1 # NOT possible in Oil because | isn't a distinct enough token to change the lexer mode var inc = |x| { return x + 1 } # This is possible but I didn't implement it. # "func" can change the lexer mode so { is known to start a block. # In other words, { and } each have two distinct token IDs. var inc = func(x) { return x + 1 } I think this is a decent tradeoff, but it's indeed tricky and something I probably spent too much time thinking about ... the perils of "familiar" syntax :-/

by chubot 7y ago

munificent 7y ago

> So Python doesn't have that issue because it doesn't overload braces for hashes and blocks. Yes, and also because lambdas in Python can only have expression bodies, not statements. That means you can never have a statement nested inside an expression. This is important because Python's rule to ignore all newlines between parentheses would fall apart if you could stuff a statement-bodied function inside a parenthesized expression.

chubot 7y ago
Yes the lambda issue is something I ran into for Oil. Although this part of the language is deferred, the parser is implemented: # Ruby/Rust style lambda, with the Python constraint that the body can only be an expression var inc = |x| x + 1 # NOT possible in Oil because | isn't a distinct enough token to change the lexer mode var inc = |x| { return x + 1 } # This is possible but I didn't implement it. # "func" can change the lexer mode so { is known to start a block. # In other words, { and } each have two distinct token IDs. var inc = func(x) { return x + 1 } I think this is a decent tradeoff, but it's indeed tricky and something I probably spent too much time thinking about ... the perils of "familiar" syntax :-/