Clojure: Forms
Lisp-like languages are said to be languages without syntax. Of course, they have a syntax, but it is as primitive as possible, actually consisting of lists and values. In addition, Lisp languages do not have keywords and their corresponding constructs. In popular languages, there are many control constructions, such as conditions, loops, returns, variable assignments, and more. Lisp-like languages have no such constructs (this does not mean that you can't implement a loop or write a condition in Clojure!)
So how does Clojure know what it's working with now and what to do? It's all about forms. Any correct Lisp program is called a form. For example:
;forms
(println "some-str")
(+ 1 2 3)
(- 3)
8
"hello world!"
; not forms, program will fail with error
(1 2)
Execution error (ClassCastException) at user/eval1 (REPL:1).
class java.lang.Long cannot be cast to class clojure.lang.IFn (java.lang.Long is in module java.base of loader 'bootstrap'; clojure.lang.IFn is in unnamed module of loader 'app')
There are only two forms: normal and composite. The normal form corresponds to all values (and definitions, which we will get to know later) because they evaluate to themselves, e.g., the number 8 or the string "hello". A compound form is a list that needs to be processed (evaluated) in one way or another.
Instructions
Print to the standard output stream (using the println function) the result of the following expression: - 23 * (- 3) + 15
The exercise doesn't pass checking. What to do? 😶
If you've reached a deadlock it's time to ask your question in the «Discussions». How ask a question correctly:
- Be sure to attach the test output, without it it's almost impossible to figure out what went wrong, even if you show your code. It's complicated for developers to execute code in their heads, but having a mistake before their eyes most probably will be helpful.
In my environment the code works, but not here 🤨
Tests are designed so that they test the solution in different ways and against different data. Often the solution works with one kind of input data but doesn't work with others. Check the «Tests» tab to figure this out, you can find hints at the error output.
My code is different from the teacher's one 🤔
It's fine. 🙆 One task in programming can be solved in many different ways. If your code passed all tests, it complies with the task conditions.
In some rare cases, the solution may be adjusted to the tests, but this can be seen immediately.
I've read the lessons but nothing is clear 🙄
It's hard to make educational materials that will suit everyone. We do our best but there is always something to improve. If you see a material that is not clear to you, describe the problem in “Discussions”. It will be great if you'll write unclear points in the question form. Usually, we need a few days for corrections.
By the way, you can participate in courses improvement. There is a link below to the lessons course code which you can edit right in your browser.