4 ms·

Is dynamic scope hard to understand or be explained or isn't it just the case that most find it to be a terrible idea for general purpose software development?

• aardvark179 4y ago
  It does seem hard to explain to people, and although I agree it is not normally the right answer, it is often a better answer than simple thread local variables.
• eadmund 4y ago
  > Is dynamic scope hard to understand or be explained or isn't it just the case that most find it to be a terrible idea for general purpose software development? I think that dynamic scope is strictly better than global variables: all of its downsides are shared by globals, but it has the important advantage that a dynamic binding is scoped. Given that every popular language I am aware of supports globals in some form, I think that adopting dynamic scope would be an improvement. Even more interesting is to consider what would it would mean to replace global with dynamic scoping entirely. I don’t really know if that is possible or efficient, but it certainly is intriguing. Almost like dependency injection throughout the language. Kinda sorta kinda.
  • skybrian 4y ago
    I think Go's context objects serve a similar purpose to dynamic scope? https://pkg.go.dev/context https://pkg.go.dev/context It seems like pretty much anything that lets you pass in an environment as a function parameter would work.
    • agumonkey 4y ago
      I believe dynamic variables are reinvented every year. Even dependency injection seems like a sibling.
  • gpderetta 4y ago
    Implicit parameters seems to be the principled dynamic scoping for statically typed languages. Implicit parameters are in the list of must-have features for the programming language I'll never get around to implement.
  • samatman 4y ago
    This is effectively how globals are handled in Lua: they are first-class environments, ordinary tables which can be assigned to a function (5.1/LuaJIT) or upvalue (5.2+) to resolve globals. I like it a lot, it's a supplement to lexical scope: like ordinary globals it's a flat namespace 'behind' the locals, unlike many implementations of globals these environments are replaceable and (mostly) fungible.
• CoastalCoder 4y ago
  I'm surprised that dynamic vs. lexical scope is hard for seasoned programmers / computer-scientists to grasp. Maybe it's because the two concepts are inter-related during program execution? Similar to the way that latency vs. bandwidth can confuse some people, because they're inter-related in some circumstances but not others?
• slaymaker1907 4y ago
  It is definitely useful for things like semi-global options like a variable for the current stdout.