epicours/Algo/Séminaire/Chapter 4 - A bit of imperative.md

0.1. Print

If we want to print something in CAML, we have to use this structure

# print_string "Hello World!";;
Hello! - : unit=()

# print_int ;;
-: int -> unit = <fun>

(*expression*)
# print_[type] [things to print];;
[things to print] -: unit=()

Difference between compiler and interpreter for print

flowchart LR

A[CAML] -- compile --> B[ ] -- exec --> C[standard output] & D[standard error] ~~~ E(on your terminal)

flowchart LR

A[CAML] -- interpreter --> B[standard error] & C[standard output] & D[CAML answer] ~~~ E(in the interpreter interface)

To print something and create a new line for the CAML evaluation

# print_endline "toto";;
toto
-: unit = ()

To just print a newline

# print_newline();;
-: unit = ()

0.2. Sequence of prints

# print_string "The answer is: "; print_int 42;;
The answer is: 42 -: unit = ()

# 3*2*7; print_string "The answer is : ";;
The answer is -: unit = () 
Warning 10 [non-unit-statement]: this expression should have type unit.

# print_string "The answer is: "; 3*2*7;;
The answer is: -:int = 42