Dynamic type languages versus static type language

Question

What are the advantages and limitations of dynamic type languages compared to static type languages?

See also: whats with the love of dynamic languages (a far more argumentative thread...)

Answer 1

Static Typing: The languages such as Java and Scala are static typed.

The variables have to be defined and initialized before they are used in a code.

for ex. int x; x = 10;

System.out.println(x);

Dynamic Typing: Perl is an dynamic typed language.

Variables need not be initialized before they are used in code.

y=10; use this variable in the later part of code

Answer 2

Perhaps the single biggest "benefit" of dynamic typing is the shallower learning curve. There is no type system to learn and no non-trivial syntax for corner cases such as type constraints. That makes dynamic typing accessible to a lot more people and feasible for many people for whom sophisticated static type systems are out of reach. Consequently, dynamic typing has caught on in the contexts of education (e.g. Scheme/Python at MIT) and domain-specific languages for non-programmers (e.g. Mathematica). Dynamic languages have also caught on in niches where they have little or no competition (e.g. Javascript).

The most concise dynamically-typed languages (e.g. Perl, APL, J, K, Mathematica) are domain specific and can be significantly more concise than the most concise general-purpose statically-typed languages (e.g. OCaml) in the niches they were designed for.

The main disadvantages of dynamic typing are:

• Run-time type errors.

• Can be very difficult or even practically impossible to achieve the same level of correctness and requires vastly more testing.

• No compiler-verified documentation.

• Poor performance (usually at run-time but sometimes at compile time instead, e.g. Stalin Scheme) and unpredictable performance due to dependence upon sophisticated optimizations.

Personally, I grew up on dynamic languages but wouldn't touch them with a 40' pole as a professional unless there were no other viable options.

Answer 3

From Artima's Typing: Strong vs. Weak, Static vs. Dynamic article:

strong typing prevents mixing operations between mismatched types. In order to mix types, you must use an explicit conversion

weak typing means that you can mix types without an explicit conversion

In the Pascal Costanza's paper, Dynamic vs. Static Typing — A Pattern-Based Analysis (PDF), he claims that in some cases, static typing is more error-prone than dynamic typing. Some statically typed languages force you to manually emulate dynamic typing in order to do "The Right Thing". It's discussed at Lambda the Ultimate.