Elements
Clojure is very different from imperative languages such as Java / C / Go. A Clojure program is represented entirely as a data structure.
Elements of Clojure
Let’s first look at how Clojure represents data in its source file.
Data in Clojure source file
Literals: numbers, strings, characters
- They have the same representation as Java.
Lists
- Lists are specified by parentheses ‘(’ and ‘)’.
Vectors
- Vectors are like arrays. They are enclosed by ‘[’ and ‘]’.
Hashmaps
- Hashmap are also called dictionaries. They store key-value pairs. Anything can be a key. Hashmaps are given as
{ <key> <value> <key> <value> ... }Symbols
Symbols are commonly known as variables. We will use the terminology symbols as they are part of data specification.
- This makes that we can generate symbols at runtime.
- We can also define symbols in the source code - just like Java.
My personal favourite feature of Clojure is amazingly generous naming rule.
The following are all valid symbol names:
get-record-from-idid->recordx,x',x''<--*-->: Yes, you can have a symbol like this. It’s crazy.∮: Yes, this can be valid Clojure code:(∮ x' dx)
Keywords
- Keywords are another unique feature of Clojure. They are equivalent to the Java enum values.
:age
:runtime-port- Keywords are great to be used as hashmap keys. Keyword-key lookup in done in constant time.
Binding & Scoping
Binding
- Symbols are placeholders. They are associated with data. The association of a symbol to a value is called a binding.
Don't forget that data can be many things include other symbols.
Scopes
- Clojure organizes its code into nested scopes using various programming constructs. So, the value that a symbol is bound to depends on the scope that the resolution is performed in.
