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That means that for every incrementer you create, you've also got to allocate two additional functions: value and increment. They have to be distinct objects, b

by rictic 8y ago

That means that for every incrementer you create, you've also got to allocate two additional functions: value and increment. They have to be distinct objects, because `incrementer().value === incrementer().value` must yield false. Debugging is also harder. When you're debugging and you find an incrementer somewhere else in your program (maybe somewhere unexpected), how do you know what kind of thing you have? All you can tell is that it's got a value and an increment method, so you've got to do a bunch of grepping over your source to find where it comes from. If it were a class instance you could ask instance.constructor.name to find out that it's an Incrementer, so you can grep for `class Incrementer`. Yes, lambda can do everything, which is really cool to learn! But lambda isn't the ultimate. More specialized tools often carry benefits.

strainer 8y ago
Comparing these function references: `a_inc_instance.value === b_inc_instance.value` is true in javascript when the function `value` is a class method. In the closure/factory created version it is false - each function `value` is a different instance with a different reference. That will involve unnecessary duplication in the interpreter, but also allows for the function to be optimised for its state (monomorphic etc) which can be significant when more than a simple example `x++` operation is involved. So the class version does entail less memory usage, but the closure permits more JIT optimisation. > If it were a class instance you could ask instance.constructor.name to find out that it's an Incrementer, so you can grep for `class Incrementer`. Im not sure how much extra help that kind of thing is, we might instead grep for `symbol\s*=` to find where a symbol was assigned whether it had a .constructor.name property or not. I can see it is a general advantage of having more types, to have summary information besides the names.

by rictic 8y ago

strainer 8y ago

Comparing these function references: `a_inc_instance.value === b_inc_instance.value` is true in javascript when the function `value` is a class method. In the closure/factory created version it is false - each function `value` is a different instance with a different reference. That will involve unnecessary duplication in the interpreter, but also allows for the function to be optimised for its state (monomorphic etc) which can be significant when more than a simple example `x++` operation is involved. So the class version does entail less memory usage, but the closure permits more JIT optimisation. > If it were a class instance you could ask instance.constructor.name to find out that it's an Incrementer, so you can grep for `class Incrementer`. Im not sure how much extra help that kind of thing is, we might instead grep for `symbol\s*=` to find where a symbol was assigned whether it had a .constructor.name property or not. I can see it is a general advantage of having more types, to have summary information besides the names.