Geek asks and answers

Haskell semantics undefined

I am new to Haskell and its semantics. I found out that not every function can be associated with an object. For instance:

square :: Int -> Int 
square x = x*x

The square value is mapped to a mathematical object. However, for any function, we endlessly correlate it with a special mathematical value ⊥. I want to know what happens if I have to do calculations with this undefined value. For example, I have a set of numbers Z⊥ ={⊥, 1,0,-1}. What will be the way out if I multiply ⊥by 1? Since the type ⊥will be undefined, can I do multiplication with a well-defined type? Since it ⊥is in the area Z⊥, I think I can do the multiplication. But then he will have to come back ⊥! I would like to have some recommendations regarding this!

+3
source share
1 answer

Multiplication will also return ⊥. It behaves exactly as you described; any calculation depending on the value ⊥will also give ⊥.

2 * undefined ~= undefined

The lower value is a resident of each type and, therefore, is an implicit member of each value and cannot be excluded by types (except for the use of internal GHC primitives). The reason for this special meaning is the ability to argue about the stopping problem in Haskell; without this value, the compiler would have to prove that a certain calculation is completed so that it can check the type, and this is generally impossible.

+5
source

More articles:


All Articles