What does it mean when we say a language is dynamically typed versus statically typed?

 

When we say a programming language is dynamically typed or statically typed, we are referring to how the type of a variable or expression is determined and checked in the language. These terms describe the behavior of the language with respect to type checking at different stages of the program's lifecycle:

1. Dynamically Typed Language:

   • In a dynamically typed language, the data type of a variable is determined and checked at runtime, which means it happens while the program is running.
   • You can change the type of a variable during the execution of the program.
   • Type errors often manifest as runtime errors.
   • Examples of dynamically typed languages include Python, JavaScript, and Ruby.

   Here's an example in Python, a dynamically typed language:

   python

x = 5  # x is dynamically assigned an integer
x = "Hello"  # x is dynamically reassigned a string

Statically Typed Language:

• In a statically typed language, the data type of a variable is determined and checked at compile-time, which means it happens before the program is executed.
• Once a variable is declared with a specific type, it cannot change its type.
• Type errors are often caught at compile-time, preventing the program from running if there are type mismatches.
• Examples of statically typed languages include C++, Java, and C#.

Here's an example in Java, a statically typed language:

java

2. int x = 5;  // x is statically declared as an integer
   x = "Hello";  // This would result in a compile-time error
   

In the dynamically typed Python example, you can see that the same variable x first holds an integer value and then a string value. The type of x is determined and checked at runtime, allowing for this flexibility.

In the statically typed Java example, the variable x is explicitly declared as an integer, and trying to assign a string value to it results in a compile-time error. The type of x is determined and checked at compile-time, providing stricter type checking.

The choice between dynamically typed and statically typed languages comes with trade-offs. Dynamically typed languages often offer more flexibility but can lead to runtime errors if not used carefully. Statically typed languages provide strong type checking at compile-time, catching type-related errors before execution, but may require more explicit type declarations and can be less flexible in certain scenarios. The choice depends on the specific needs and design goals of a given project or programming language.