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There's also Eric Lippert's blog series on OOP and business rules [1] that culminates [2] in suggesting a DSL with Inform7 as a possible candidate. The comment

There's also Eric Lippert's blog series on OOP and business rules [1] that culminates [2] in suggesting a DSL with Inform7 as a possible candidate. The comments on the final post are great as people rail against the use of a DSL. [1] https://ericlippert.com/2015/04/27/wizards-and-warriors-part-one/ https://ericlippert.com/2015/04/27/wizards-and-warriors-part... [2] https://ericlippert.com/2015/05/11/wizards-and-warriors-part-five/ https://ericlippert.com/2015/05/11/wizards-and-warriors-part...

all2 5y ago
I started working with C# about 6 months ago. I'd read that post before, but I'm only just now understanding it. I think I really missed the boat when it comes to things like OO programming patterns. I'm still kinda fuzzy on the visitor pattern he mentioned. I think I get it? The abstraction he offered, of having a tree and then visiting every node in that tree, made the most sense. > One of the most common usages of this pattern is for the scenario where you’ve got a complex tree where tree nodes can be of many types, and you wish to traverse the tree — that is, visit every node in the tree — taking some actions or performing some computations as you go. The “double dispatch” part of it is that the actions you take as you visit nodes in the tree can depend on the runtime types of both the nodes in the tree, and the code performing the action. That sounds like a parser. It accepts an AST and evaluates productions on its way through. Saying "actions you take ... depend on the runtime types of ... nodes ... and the code performing the action" sounds similar to sorting out how to mash tree-traversal and productions together. In my compilers class we first wrote a code linter for our "Wombo" language (a simplified Java). Then we wrote something that built an AST. The core tree traversal code was the same, but the "productions" paired with nodes were different.

all2 5y ago

I started working with C# about 6 months ago. I'd read that post before, but I'm only just now understanding it. I think I really missed the boat when it comes to things like OO programming patterns. I'm still kinda fuzzy on the visitor pattern he mentioned. I think I get it? The abstraction he offered, of having a tree and then visiting every node in that tree, made the most sense. > One of the most common usages of this pattern is for the scenario where you’ve got a complex tree where tree nodes can be of many types, and you wish to traverse the tree — that is, visit every node in the tree — taking some actions or performing some computations as you go. The “double dispatch” part of it is that the actions you take as you visit nodes in the tree can depend on the runtime types of both the nodes in the tree, and the code performing the action. That sounds like a parser. It accepts an AST and evaluates productions on its way through. Saying "actions you take ... depend on the runtime types of ... nodes ... and the code performing the action" sounds similar to sorting out how to mash tree-traversal and productions together. In my compilers class we first wrote a code linter for our "Wombo" language (a simplified Java). Then we wrote something that built an AST. The core tree traversal code was the same, but the "productions" paired with nodes were different.