OCaml is a value-based; strongly, statically, implicitly typed; functional programming language

4.1 OCaml expressions have values

• integer negation is with the ~- operator
• full set of operators is provided in OCaml’s Stdlib module (standard library so the values it provides can be referred to anywhere without any additional qualification)

# 1001 / 365 ;; (* # of years in 1001 nights *)
- : int = 2
# 1001 mod 365 ;; (* # of nights left over *)
- : int = 271
# 1001 - (1001 / 365) * 365 ;; (* ...or alternatively *)
- : int = 271

• floating point literals can be expressed using decimal notation, with an exponent, and even in hexadecimal

# 3.14 ;;
- : float = 3.14
# 314e-2 ;;
- : float = 3.14
# 0x1.91eb851eb851fp+1 ;;
- : float = 3.14

• addition (+.), subtraction (-.), multiplication (*.), division (/.), and negation (~-.)
• character literals are given in single quotes: ‘a’, ‘x’, ‘3’
• ‘\n’ - new line or ‘\t’ - tab space
• string literals are given in double quotes: “first” and can be concatenated with the ^ operator

# "" ^ "first" ^ " and second" ;;
- : string = "first and second"

• truth values: true and false
• operators for conjunction (&&), disjunction (||), and negation (not)
• comparative operators for =, <, >, ≤, ≥, or <> (not equal)
• conditional expressions: if ⟨exprtest⟩ then ⟨exprtrue⟩ else ⟨exprfalse⟩

# if 3 = 3 then 0 else 1 ;;
- : int = 0
# 2 * if 3 > 4 then 3 else 4 + 5 ;;
- : int = 18
# 2 * (if 3 > 4 then 3 else 4) + 5 ;;
- : int = 13

4.2 OCaml expressions have types

OCaml is a typed language, meaning that every expression of the language is associated with a type; specifically, OCaml is statically typed, in that the type of an expression can be determined just by examining the expression in its context. On the other hand, Python is dynamically typed, meaning that it is necessary to run the code in which an expression occurs in order to determine the type of an expression