Erlang

Question 1

erlang og need

Answer 1

telecom systems where reliability, responsiveness, scalability, and constant availability were needed

Question 2

nature of erlang programs

Answer 2

immutable data, pattern matching, functional programming, garbage collector

Question 3

sequential subset of erlang lang supports

Answer 3

eager evaluation, single assignment, dynamic typing

Question 4

normal erlang application built out of

Answer 4

thousands of small erlang programs

Question 5

BEAM

Answer 5

virtual machine at core of erlang
part of run time system

.beam file extension

Question 6

Erlang run time system (ERTS) compiles

Answer 6

erlang source code into bytecode which runs on BEAM

Question 7

ERTS designed for systems with these traits:

Answer 7

distributed, fault tolerant, soft real time, highly available non stop apps, hot swapping

Question 8

what makes erlang processes “living” objects

Answer 8

data encapsulation, message passing and capable of changing behavior during runtime (hot swapping)

Question 9

thread of execution

Answer 9

process

Question 10

how does erlang communicate

Answer 10

asynch signaling

Question 11

most commonly used signal

Answer 11

message

Question 12

other common signals

Answer 12

exit, link, unlink, monitor, demonitor

Question 13

basic unit of concurrency

Answer 13

process

Question 14

process

Answer 14

lightweight thread of execution that runs independently and communicates with other processes through message passing

Question 15

how are processes created

Answer 15

spawn function -> takes function as an argument and returns process identifier (pid)

Question 16

what is a program a call to

Answer 16

call to an initial function

Question 17

how are processes scheduled

Answer 17

virtual machine (vm)

Question 18

erlang: let it crash or let it fail

Answer 18

let it fail -> less code devoted to defensive programming

Question 19

design philosophy

Answer 19

systems -> expect failure to happen, build supervisor structure to monitor executions, detect failures, and restart failed processes

Question 20

variables

Answer 20

sequence of characters, must begin with uppercase letter

Question 21

are variables single assignment

Answer 21

yes, value cannot be changed once assigned

Question 22

atoms

Answer 22

sequence of characters, must begin with lowercase

Question 23

functions

Answer 23

named sequences of expressions to be evaluated

Question 24

modules

Answer 24

primary mechanism for organizing erlang code -> contain func defs

Question 25

basic data types

Answer 25

atom, int, float, binary, pid, port, fun

Question 26

structured types

Answer 26

list: dynamic mixed collection [] tuple: fixed-length mixed collection {}

Question 27

pattern matching

Answer 27

used in function parameter binding

Question 28

guards

Answer 28

used to partially define function clauses

Question 29

io:format("~s~p~n"["age: ", 45]). what does this do

Answer 29

~n -> newline ~p -> numeric data ~s -> string data

Question 30

module consists of

Answer 30

sequence of attributes and function declarations

Question 31

what do modules get compiled into

Answer 31

nameoffile.beam

Question 32

function declaration

Answer 32

sequence of function clauses separated by semicolons and terminated by period

Question 33

what does a function clause consist of

Answer 33

head and body separated by ->

Question 34

clause head

Answer 34

func name, argument list, optional guard sequence beg with keyword when

Question 35

sequential scope

Answer 35

variables are accessible after they are bound

Question 36

nested scope

Answer 36

inner expressions dont leak variables to outer ones

Question 37

t/f: no global variables

Answer 37

true, everything is local to the func, mod, or process

Question 38

t/f: processes can share variables

Answer 38

false, its all local to process scope

Question 39

pattern matching scope

Answer 39

case, receive, if expressions -> vars are bound to one branch only