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The author's basic complaint with the Javascript switch statement is that it's essentially a structured series of 'goto' statements. They think that each 'case

by rovolo 8y ago

The author's basic complaint with the Javascript switch statement is that it's essentially a structured series of 'goto' statements. They think that each 'case' should behave as an 'if-else' where each case has its own lexical scope, and the control flow doesn't leak from one case to another. They think that pattern matching is a better model for 'switch' in practice. How often do you use a 'switch' statement whose cases don't always end in 'return' or 'break'? The "coroutines in C" [0] article is a clever use of switch-case as a goto, but it seems like you need to invent new types of control flow to use 'goto' properly. Does anyone have other clever uses of 'switch'? [0] https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html

ioddly 8y ago
> How often do you use a 'switch' statement whose cases don't always end in 'return' or 'break'? I do, occasionally. I prefer the inverted golang switch where fallthrough needs to be specified, since these cases (heh) are generally the minority.
xahrepap 8y ago
I would like it better if switch statements used the keyword `continue` to fallthrough and `break` is implied. Switch statements are much easier to maintain if you keep them one or two lines long, and just have it immediately delegate to a function call then break. I think that's true for almost any code-flow syntax: if/elseif/else blocks, various loops. They all break down quickly if you have too much in them.
ivyirwin 8y ago
I agree. Their complaint on the use cases (pun!) for switch seem to ignore the flexibility of the syntax. I don't think the requirement to include breaks/returns is a problem if you know how it's intended to work. I prefer switches for the easy to follow flow but also the ability to "waterfall" multiple conditions, which is syntactically clunky with other approaches.
ricardobeat 8y ago
This is my favorite from a library I wrote ~6 years ago: https://github.com/ricardobeat/require-tree/blob/master/index.js#L16-L22 https://github.com/ricardobeat/require-tree/blob/master/inde... The goal is to accept a 'filter' argument that can either be a string, an array of strings, a regular expression, or a filter function. It fully uses fall-through and the multiple entry points. I find it magical, in that it turns all of those into a function so the remainder of the code doesn't have to care, and it's not any less efficient. Similar feeling to finding a use case for 'Infinity' :) switch (type(filter)) { case 'array' : filter = filter.join('|') case 'string' : filter = new RegExp('^('+filter.replace('*', '.*')+')$', 'i') case 'regexp' : filter = filter.exec.bind(filter) case 'function' : return filter }
- fc88 8y ago
  This is one of the most amazing pieces of code I have ever seen

by rovolo 8y ago

ioddly 8y ago

> How often do you use a 'switch' statement whose cases don't always end in 'return' or 'break'? I do, occasionally. I prefer the inverted golang switch where fallthrough needs to be specified, since these cases (heh) are generally the minority.

xahrepap 8y ago

I would like it better if switch statements used the keyword `continue` to fallthrough and `break` is implied. Switch statements are much easier to maintain if you keep them one or two lines long, and just have it immediately delegate to a function call then break. I think that's true for almost any code-flow syntax: if/elseif/else blocks, various loops. They all break down quickly if you have too much in them.

ivyirwin 8y ago

I agree. Their complaint on the use cases (pun!) for switch seem to ignore the flexibility of the syntax. I don't think the requirement to include breaks/returns is a problem if you know how it's intended to work. I prefer switches for the easy to follow flow but also the ability to "waterfall" multiple conditions, which is syntactically clunky with other approaches.

ricardobeat 8y ago

This is my favorite from a library I wrote ~6 years ago: https://github.com/ricardobeat/require-tree/blob/master/index.js#L16-L22 https://github.com/ricardobeat/require-tree/blob/master/inde... The goal is to accept a 'filter' argument that can either be a string, an array of strings, a regular expression, or a filter function. It fully uses fall-through and the multiple entry points. I find it magical, in that it turns all of those into a function so the remainder of the code doesn't have to care, and it's not any less efficient. Similar feeling to finding a use case for 'Infinity' :) switch (type(filter)) { case 'array' : filter = filter.join('|') case 'string' : filter = new RegExp('^('+filter.replace('*', '.*')+')$', 'i') case 'regexp' : filter = filter.exec.bind(filter) case 'function' : return filter }

fc88 8y ago
This is one of the most amazing pieces of code I have ever seen