I am not a big fan of functional programming language. I do not think it is easy to use, nor it is high performant. As to its completeness, I do not think it is very strong. Then why are there so many people obsessed by this kind of such "unpractical" programming language?
neonachronism
A big reason is because it maps very nicely on to logic, so its easy to formally analyze code, and its very natural if you have a background in logic. However, regular programers use things like higher order functions and closures. Also, with new "hybrid" languages like Rust, the practicality is going up.
bob_sacamano
It's not a necessity but it's common to have functional languages that follow immutable semantics - you can never modify the value a variable takes. This makes it very unlikely to have unpredictable behavior in your programs. Along with the intuitive flow of logic that @neonachronism mentioned, you can be almost certain that your program will be semantically correct once it compiles.
I am not a big fan of functional programming language. I do not think it is easy to use, nor it is high performant. As to its completeness, I do not think it is very strong. Then why are there so many people obsessed by this kind of such "unpractical" programming language?
A big reason is because it maps very nicely on to logic, so its easy to formally analyze code, and its very natural if you have a background in logic. However, regular programers use things like higher order functions and closures. Also, with new "hybrid" languages like Rust, the practicality is going up.
It's not a necessity but it's common to have functional languages that follow immutable semantics - you can never modify the value a variable takes. This makes it very unlikely to have unpredictable behavior in your programs. Along with the intuitive flow of logic that @neonachronism mentioned, you can be almost certain that your program will be semantically correct once it compiles.