I have two nested loops like this: loop1 do ... loop2 do ... break if cond ... end ... end Here, the break just gets me out of the inner loop2 but I want to get out of both. I have a cludge way of doing that, but does Crystal provide an elegant way to break out of both?

There’s also the thing that if we allow breaking from an inner loop then we need to think about how the type inference/flow changes. All type inference done up until the “break” point is carried over outside, which makes the compiler and the language harder to implement and understand.

[image] straight-shoota: I suppose this could be solved with throw / catch but really a more direct solution would be a nesting value for break . In PHP for example, you can pass a number to break which determines how many nested levels of loops it should break. break can be extended, without…

Will something like the following work for you? Caveat: it breaks to the specific place but holds no value. But perhaps for your uses you can adapt my solution… class Break < Exception getter symbol : Symbol def initialize(@symbol : Symbol) end end def catch(symbol : Symbol) begin yie…

When @matthewmcgarvey was porting Roda to Crystal he actually implemented throw / catch because that’s how Roda bails on processing the request. He uses LibUnwind directly to avoid generating a stack trace, which IIRC was the most expensive part of raising an exception, so it should theoretically be…

If you want to avoid a stack trace, there’s no need to use libunwind directly. You just need to assign a value to the exception’s callstack property before raising.

[image] beta-ziliani: Will something like the following work for you? Caveat: it breaks to the specific place but holds no value. But perhaps for your uses you can adapt my solution… I tried it, and it works. But - catch :here || catch(:here) - produces error. In catchtest.cr:59:3 59 | c…

Sorry, I missed to explain my code and that lead you to the wrong application. In order to work properly, the code must be enclosed in a block. The symbol is not a label in a goto sense, just a mark to say “if the code that the block is executing raises this particular label, then rescue it, otherw…

Ah that explains the slow times. After running some benchmarks, the original code took ~50s, the code using nested break statements took ~60s, and my implementation using code your took ~255s. I’ll try the way you just showed and see what happens.

Nothing is going to be faster than your original code.

Elegant breaking from nested loops

Help & Support

jgaskins February 9, 2022, 7:48pm 19

Found the thread where it was discussed before. I couldn’t remember the details.

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Elegant breaking from nested loops

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