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Lua is a simple and only slightly quirky (1-based arrays) dynamic programming language. It has exceptionally small and high quality implementations in Lua and

Lua is a simple and only slightly quirky (1-based arrays) dynamic programming language. It has exceptionally small and high quality implementations in Lua and LuaJIT. It has very good documentation. Its main downside is that the language changes in backward-compatible ways between releases. And worse, LuaJIT has in some sense forked the language. Lua 5.3 introduced integer support, but there are no plans to add this to LuaJIT AFAIK.

vbit 11y ago
The 1-based indexing isn't particularly bothersome. It's the method vs. function determination at call site combined with default nil for unspecified arguments that really gets you.
- haberman 11y ago
  I've never had any problem with the two things you mentioned.
- jnbiche 11y ago
  > default nil for unspecified arguments Isn't this what most scripting languages do? I know it's the case with Python and PHP. And I disagree about the 1-based array indexing. With algorithms that require a lot of 1-off values, it can be a huge pain in the ass, particularly if you're trying to integrate it with C (and its 0-based array indexing). Still not sure why the creators chose it, given that Lua was designed for easy and close C interop.
  - ewmailing 11y ago
    Why? From one of Roberto Ierusalimschy's talks (starts at slide 6): http://www.inf.puc-rio.br/%7Eroberto/talks/ws2011.pdf http://www.inf.puc-rio.br/%7Eroberto/talks/ws2011.pdf Excerpt: - Not all languages are 0-based: Icon, Fortran, AWK1, and Smalltalk are 1-based; Snobol, Pascal, Modula, Modula-32, and Ada have configurable bases. - Currently, many languages are 0-based due to influence from C. - Ironically, none of them share the reason that made C 0-based (where a[e] means *(a+e)). 1-based arrays: - Much more intuitive: first is 1st (not 0th). ISO-C: “E1[E2] designates the E2-th element of E1 (counting from zero).” - Much easier for non programmers. Easy for (good) programmers :) - Historical reason: Fortran used 1-based arrays, and most first users of Lua had a Fortran background.
    - kbd 11y ago
      The presentation asserts that 0-based arrays have "More interesting mathematical properties". Dijkstra's classic paper on this is a must-read: http://www.cs.utexas.edu/users/EWD/ewd08xx/EWD831.PDF http://www.cs.utexas.edu/users/EWD/ewd08xx/EWD831.PDF
  - rkrzr 11y ago
    > Isn't this what most scripting languages do? I know it's the case with Python and PHP. This is false for Python: >> print bla NameError: name 'bla' is not defined In Lua: > = bla nil
    - pygy_ 11y ago
      That's yet another source of nil, but it can be fixed with modules like strict.lua, or simply setmetatable(_G or _ENV, {__index = error}) -- `error` for the example, you can write a function that prints a better error message.
  - vbit 11y ago
    Python errors out if you don't specify all arguments. >>> def f(a): ... pass ... >>> f() Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: f() takes exactly 1 argument (0 given) >>> I agree 1-based indexing isn't ideal, but in the grand scheme of things, the default nils and the method/function syntax are a constant source of mistakes and frustration for me. In Lua you have to call `obj:method()` which to pass `obj` as the first argument. If you accidentally do `obj.method()` - there is no error, but the first argument becomes `nil`. In Python, there the call syntax is consistent and `obj` is automatically passed as the first argument for methods.
    - pygy_ 11y ago
      > but the first argument becomes `nil` s/first/last/, the arguments will be shifted to the right. But yes, it can be annoying.
  - jnbiche 11y ago
    Thanks for the corrections. I've been switching a lot between Lua and Python for the past year and have clearly gotten some things mixed up.
ewmailing 11y ago
Speaking to its small and high quality implementations, Verisign gave a talk on how they used it for their high availability/performance servers. Rather than the usual throw more hardware redundancy at the problem, they went the other extreme and audited and understood every line of code in Lua so they could create a reliable system by eliminating bugs. And Wikipedia (Wikimedia) uses Lua for their multimedia scripting engine. Besides good performance, the implementation was good and small enough that it could be audited for security.

vbit 11y ago

The 1-based indexing isn't particularly bothersome. It's the method vs. function determination at call site combined with default nil for unspecified arguments that really gets you.

haberman 11y ago
I've never had any problem with the two things you mentioned.
jnbiche 11y ago
> default nil for unspecified arguments Isn't this what most scripting languages do? I know it's the case with Python and PHP. And I disagree about the 1-based array indexing. With algorithms that require a lot of 1-off values, it can be a huge pain in the ass, particularly if you're trying to integrate it with C (and its 0-based array indexing). Still not sure why the creators chose it, given that Lua was designed for easy and close C interop.
- ewmailing 11y ago
  Why? From one of Roberto Ierusalimschy's talks (starts at slide 6): http://www.inf.puc-rio.br/%7Eroberto/talks/ws2011.pdf http://www.inf.puc-rio.br/%7Eroberto/talks/ws2011.pdf Excerpt: - Not all languages are 0-based: Icon, Fortran, AWK1, and Smalltalk are 1-based; Snobol, Pascal, Modula, Modula-32, and Ada have configurable bases. - Currently, many languages are 0-based due to influence from C. - Ironically, none of them share the reason that made C 0-based (where a[e] means *(a+e)). 1-based arrays: - Much more intuitive: first is 1st (not 0th). ISO-C: “E1[E2] designates the E2-th element of E1 (counting from zero).” - Much easier for non programmers. Easy for (good) programmers :) - Historical reason: Fortran used 1-based arrays, and most first users of Lua had a Fortran background.
  - kbd 11y ago
    The presentation asserts that 0-based arrays have "More interesting mathematical properties". Dijkstra's classic paper on this is a must-read: http://www.cs.utexas.edu/users/EWD/ewd08xx/EWD831.PDF http://www.cs.utexas.edu/users/EWD/ewd08xx/EWD831.PDF
- rkrzr 11y ago
  > Isn't this what most scripting languages do? I know it's the case with Python and PHP. This is false for Python: >> print bla NameError: name 'bla' is not defined In Lua: > = bla nil
  - pygy_ 11y ago
    That's yet another source of nil, but it can be fixed with modules like strict.lua, or simply setmetatable(_G or _ENV, {__index = error}) -- `error` for the example, you can write a function that prints a better error message.
- vbit 11y ago
  Python errors out if you don't specify all arguments. >>> def f(a): ... pass ... >>> f() Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: f() takes exactly 1 argument (0 given) >>> I agree 1-based indexing isn't ideal, but in the grand scheme of things, the default nils and the method/function syntax are a constant source of mistakes and frustration for me. In Lua you have to call `obj:method()` which to pass `obj` as the first argument. If you accidentally do `obj.method()` - there is no error, but the first argument becomes `nil`. In Python, there the call syntax is consistent and `obj` is automatically passed as the first argument for methods.
  - pygy_ 11y ago
    > but the first argument becomes `nil` s/first/last/, the arguments will be shifted to the right. But yes, it can be annoying.
- jnbiche 11y ago
  Thanks for the corrections. I've been switching a lot between Lua and Python for the past year and have clearly gotten some things mixed up.

ewmailing 11y ago

Speaking to its small and high quality implementations, Verisign gave a talk on how they used it for their high availability/performance servers. Rather than the usual throw more hardware redundancy at the problem, they went the other extreme and audited and understood every line of code in Lua so they could create a reliable system by eliminating bugs. And Wikipedia (Wikimedia) uses Lua for their multimedia scripting engine. Besides good performance, the implementation was good and small enough that it could be audited for security.