Re: Definition of Semantic: was What Lua can do that other programming languages can't do?

[Dirk Laurie <dirk.laurie@...>]

2013/3/26 Tim Hill <drtimhill@gmail.com>:
> I would say a "semantic" bug is any deviation from expected behavior
> of a program that is grammatically correct (i.e. has correct syntax
> according to the formal grammar of the language).

I would classify bugs into five groups.

  Typographical: the program would have been correct if the symbol
    the programmer intended had been typed, but actually there is
    a different symbol in there.
  Syntactic: the compiler catches the bug.
  Semantic: the bug is caused by something in the language having
     a different meaning to what the programmer reasonably expects.
     E.g. when does an expression test "false" in a `if` statement?
     (There are four different conventions for C, Python, Lua and
     LuaJIT.) What is the precedence of operators in a expression?
     Etc.
  Logical: the bug can be found by using 'assert'. The programmer has
     (perhaps unwittingly) assumed that a certain state must exist,
     but failed take into account that it could be otherwise.
  Rot: The program used to work, but changes to the language, OS etc
     have made it invalid.