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1 Install Erlang with "sudo zypper install erlang"
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2
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3 Erlang has a REPL (erl)
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4
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5 Comments are "%", just to be different
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6
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7 Commands need to end with a full-stop (like Prolog)
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8
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9 Erlang has dynamic typing with coercion: 2 + 2 = 4, 2 + 2.0 = 4.0
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10 → BUT lists aren't just lists, they're strings when the values are printable ASCII 😮
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11 → AND numbers aren't coerced to strings
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12
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13 As well as strings there are "atoms" - arbitrarily named symbols.
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14
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15 Variables start with upper-case.
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16
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17 Variables can't be redefined. Trying results in "exception error: no match of right hand side value <the value>"
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18
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19 Lists use square brackets. Tuples use curly braces.
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20
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21 Tuples are apparently used instead of maps and hashes to associate atoms as keys with values.
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22 → Values are extracted from tuples using pattern matching
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23 → BUT this implies matching ordering (which isn't the same as maps)
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24
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25 Example:
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26 Person = {person, {name, "Agent Smith"}, {profession, "Killing programs"}}.
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27 % person, name and profession are atoms
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28 {person, {name, Name}, {profession, Profession}} = Person.
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29 Name. % prints "Agent Smith"
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30 Profession. % prints "Killing programs"
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31
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32 The initial atom is an Erlang-ism to make it easier to match all "person" tuples
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33
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34 Erlang can pack and unpack bits using "<<Variable:bit_count[ Variable:bit_count[, …]]>>" and then pattern matching to unpack
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35
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36 Functions are well documented at http://erlang.org/doc/apps/stdlib/index.html
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37
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38 Case statements use patern matching:
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39
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40 Animal = "dog".
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41 case Animal of
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42 "dog" -> underdog;
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43 "cat" -> thundercat;
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44 _ -> something_else
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45 end.
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46
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47 If statements use "guards" (conditions) and implies "elseif". Else requires a guard of "true".
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48
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49 if
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50 X > 0 -> positive;
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51 X < 0 -> negative;
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52 true -> zero
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53 end.
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54
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55 Anonymous functions are defined as "fun(Var[, …]) -> [code] end."
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56
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57 List processing is in the "lists" module - e.g. lists:foreach/2 takes function and list of values and calls function on each value in list.
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58 → There are also map, filter, all and any functions, etc.
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59 → Interesting extra functions are lists:takewhile/2 and lists:dropwhile/2, which filter or discard from the start of a list based on the function's return
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60
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61 Erlang has list comprehension - similar to Python's, but with Erlang-y syntax.
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62 → [Function(Val) || Val <- List]. % Call Function on Val for each Val in List
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63 → Can also be done without a function and just code - e.g. [X * 2 || X <- [1, 2, 3]].
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64 → Therefore, map(Func,List) can be defined as [ Func(X) || X <- List ].
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65 → EXCEPT it isn't that simple - there can be multiple clauses after the double-pipe, which can be generators (X <- List) or filter clauses (X < 3)
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66 |
