[dozzie]

> The conflation between 'strong' and 'static', and 'weak' and 'dynamic', is probably terminal at this point,

Type system of C is weak and static.

Type system of JavaScript is weak and dynamic.

Type system of Lisp is strong and dynamic.

Type system of OCaml is strong and static.

Type system of Python is dynamic. It may be strong or weak, depending on your opinion about duck typing (does it weaken the type system or not?).

[kazinator]

The "weak" terminology has a flaw because it sometimes means "leaves type errors undetected, with undefined behavior" and sometimes it refers to a situation whereby a character string like "3.14" can be treated as a number and such.

Awk and Perl are not weakly typed in the same sense that C is weakly typed.

[kazinator]

There is also the related aspect of conversions. Ada is said to be stronger than C even if we ignore the "holes in the type system" of C because it doesn't allow implicit conversions (conversions without an explicit conversion operator or casting syntax). Though C won't treat a "3.14" character string as a number, it implicitly converts among numbers of different kinds, and converts between void * and object pointers. Narrowing conversions silently discard data ("implementation-defined result"), and so do conversions between same size but different signedness. Out-of range conversions between integer and floating-point values can trigger undefined behavior. (These issues are still there when the conversions are explicit, but when the conversion are implicit, the issues can sneak into the code more easily by accident).

Though Lisp was listed in the grandparent posting as "strongly typed", it also has something similar to C's implicit conversions:

  [1]> (sin 42)
  -0.91652155
  [2]> (sin 42.0)
  -0.91652155
  [3]> (+ 1 2.0)
  3.0

Unlike C, it won't go from floating to integer:

  [4]> (evenp 3.0)

  *** - EVENP: 3.0 is not an integer

Whereas if we had an

  bool evenp(int arg);

function in C and called it as

  evenp(3.0);

or even

  evenp(3.1);

it would work.