Keywords and Symbols

1:status
2:user/id            ; namespaced keyword (helps avoid collisions)

1(def m {:status :ok})
2
3(:status m) ; => :ok   ; keyword-as-function lookup
4(get m :status)

1(def status :ok)
2
3status   ; => :ok     ; resolves to a var’s value
4'status  ; => status  ; quoted symbol (data, not lookup)

1(+ 1 2)  ; here `+` is a symbol that resolves to a function

### Which statement is true about keywords? - [x] A keyword like `:k` evaluates to itself and is commonly used as a map key. - [ ] A keyword like `:k` must be defined with `def` before it can be used. - [ ] Keywords resolve to vars in a namespace. - [ ] Keywords are mutable identifiers like Java variables. > **Explanation:** Keywords are self-evaluating values and are widely used for map keys and “keyword-as-function” lookup. ### What does quoting a symbol do? (Example: `'status`) - [x] It returns the symbol as data instead of resolving it to a value. - [ ] It turns the symbol into a keyword. - [ ] It evaluates the symbol in a different namespace. - [ ] It forces compilation of the symbol. > **Explanation:** Quote prevents evaluation. You’ll see quoted symbols and lists constantly in macros and code tools. ### Why might you prefer `:user/id` over `:id` as a map key in a larger system? - [x] It reduces key collisions when maps from different domains get merged or passed around. - [ ] It makes map lookups faster on the JVM. - [ ] It makes keywords mutable. - [ ] It avoids the need for `get`. > **Explanation:** Namespacing communicates intent and reduces accidental collisions across modules and teams.