| Variable % starts with upper case Str = “John Doe”. % strings are stored as integers. atom or ‘ATOM’ |
Macros: -define(macro1, Replacement) ?macro1 % to use the macro |
| % Writing the value on output Io:format(“Name is: ~s~n”, [Str]). Io:fwrite(“Name is: ~s~n”, [Str]). ~n => new line ~s => string ~f => float ~w=>standard output. Like Object.toString(). ~p=>like ~w but breaks after each line |
Erlang Shell: c(ModuleName) % compile module on erlang shell cd(“dirname”) % change directory on shell f() to clear all existing bindings rr("records.hrl") to read a records file rf(record_name) to forget a recordd, |
| List = [1,2,3,4]. % lists NewList = [6, 7, List] % returns [6,7, [1,2,3,4]] % appends to a new list 29> [H|T] = AList. % returns the Head and Tail. H and T are Unbound variables. ["a","b",{1,2,3}] |
Records: - record(todo, {status=reminder,who=john,text}). - to create an instance of record: X = #todo{status=urgent}. - extracting values from record is similar to pattern matchingd, - X#todo.status %% to get a single value. |
| Tuple = {1.0, 2.0, 3.0} element(2, Tuple) returns 2.0 % tuple index {_, Second, _} = Tuple stored 2.0 in Second variable % pattern matching to retrieve a value |
- ++ is the infix append operator - [1] ++ [2] ++ [3] = [1,2,3] - X--Y is the list subtraction operator. It subtracts the elements of Y from X. |
| List and Tuple can contain any type. Atuple = {1,2,3}. {1,2,3} AList = ["a", "b", Atuple]. ["a","b",{1,2,3}] Anewtuple = {atom1, atom2, AList}. {atom1,atom2,["a","b",{1,2,3}] |
Use pattern matching/recursion to replace iteration. total([{What,N|T}]) -> cost(What) * N + total(T); total([]) -> 0. |
| Functions: Anonymous: F = fun(X) -> X end. % F(10) prints 10 Named: method_name(Arg) -> Arg. |
File attributes % -import, -export, -module -module(ModuleName) -export([Func_a/0, Func_b/1]). -import to import the module and methods % -import(lists, [map/2]). - Includes File: -include(Filename). % -include_lib(Name). |
| % Perform action on each element on list L = [1,2,3,4,5]. [1,2,3,4,5] lists:map(fun(X) -> 2*X end, L). % using map method of lists module [2,4,6,8,10] [2*X || X <- L]. % using list comprehensions [2,4,6,8,10] |
case Expression of Pattern1 [when Guard1] -> Expr_seq1; Pattern2 [when Guard2] -> Expr_seq2 end. |