Menu
For a homework assignment, we've been instructed to complete a task without introducing any "side-effects". I've looked up "side-effects" on Wikipedia, and though I get that in theory it means "modifies a state or has an observable interaction with calling functions", I'm having trouble figuring out specifics.
For example, would creating a value that holds a non-compile time result be introducing side effects?
Say I had (might not be syntactically perfect):
val myList = (someFunction x y);;
if List.exists ((=) 7) myList then true else false;;
Would this introduce side-effects? I guess maybe I'm confused on what "modifies a state" means in the definition of side-effects.
874
Pure and impure functional programming A pure function is one without any side-effects. A side-effect really means that the function keeps some sort of hidden state inside it. strlen is a good example of a pure function in C. If you call strlen with the same string, it always returns the same length.
OCaml supports imperative programming through the primitive parameterized ref type. A value of type "int ref" is a pointer to a location in memory, where the location in memory contains an integer. It's analogous to "int*" in C/C++ or "Integer" in Java (but not "int" in Java).
the let expression is the main way to bind a name to a value. since functions are values just like ints or strings, let is also used to define functions. to define simple values: let name = value.
At its simplest, a variable is an identifier whose meaning is bound to a particular value. In OCaml these bindings are often introduced using the let keyword.
No; a side-effect refers to e.g. mutating a ref cell with the assignment operator :=, or other things where the value referred to by a name changes over time. In this case, myList is an immutable value that never changes during the program, thus it is effect-free.
See also
http://en.wikipedia.org/wiki/Referential_transparency_(computer_science)
153
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
