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Erlang  

1 
Print a literal string on standard output


2 
Loop to execute some code a constant number of times


3 
Like a function which doesn't return any value, thus has only side effects (e.g. Print to standard output)


4 
Create a function which returns the square of an integer


5 
Declare a container type for two floatingpoint numbers x and y

module(points). export([new/2, x/1, y/1]). opaque point() :: #{x => float(), y => float()}. export_type([point/0]). spec new(float(), float()) > point(). new(X, Y) > #{x => X, y => Y}. spec x(point()) > float(). x(#{x := X}) > X. spec y(point()) > float(). y(#{y := Y}) > Y. 

6 
Do something with each item x of an arraylike collection items, regardless indexes.



7 
Print each index i with its value x from an arraylike collection items


8 
Create a new map object x, and provide some (key, value) pairs as initial content.



9 
The structure must be recursive because left child and right child are binary trees too. A node has access to children nodes, but not to its parent.


10 
Generate a random permutation of the elements of list x


11 
The list x must be nonempty.



12 
Check if the list contains the value x.
list is an iterable finite container. 
Alternative implementation:


13 
Access each key k with its value x from an associative array mymap, and print them.


14 
Pick a random number greater than or equals to a, strictly inferior to b. Precondition : a < b.


15 
Pick a random integer greater than or equals to a, inferior or equals to b. Precondition : a < b.



17 
The structure must be recursive. A node may have zero or more children. A node has access to its children nodes, but not to its parent.



19 
Reverse the order of the elements of the list x.
This may reverse "inplace" and destroy the original ordering. 


20 
Implement a function search which looks for item x in a 2D matrix m.
Return indices i, j of the matching cell. Think of the most idiomatic way in the language to return the two values at the same time. 
spec search(T, [[T]]) > {pos_integer(), pos_integer()}. search(X, M) > search(X, M, 1). search(_, [], _) > throw(notfound); search(X, [RRs], RN) > case search_row(X, R) of notfound > search(X, Rs, RN+1); CN > {RN, CN} end. search_row(X, Row) > search_row(X, Row, 1). search_row(_, [], _) > notfound; search_row(X, [X_], CN) > CN; search_row(X, [_Elems], CN) > search_row(X, Elems, CN+1). 

21 
Swap the values of the variables a and b

fun1(A, B) > do:something(), fun2(B, A). fun2(A, B) > now(A, is, B), and(B, is, A), keep:moving(). 

22 
Extract the integer value i from its string representation s (in radix 10)



23 
Given a real number x, create its string representation s with 2 decimal digits following the dot.


24 
Declare a new string s and initialize it with the literal value "ネコ" (which means "cat" in japanese)



26 
Declare and initialize a matrix x having m rows and n columns, containing real numbers.


27 
Declare and initialize a 3D array x, having dimensions boundaries m, n, p, and containing real numbers.

X = array(M, N, P). spec array(pos_integer(), pos_integer(), pos_integer()) > [[[float()]]]. array(M, N, P) > [array(M, N)  _ < lists:seq(1, P)]. array(M, N) > [array(M)  _ < lists:seq(1, N)]. array(M) > [rand:uniform()  _ < lists:seq(1, M)]. 

28 
Sort the elements of the list (or arraylike collection) items in ascending order of x.p, where p is a field of the type Item of the objects in items.

sort_by_birth(ListOfMaps) > lists:sort( fun(A, B) > maps:get(birth, A, undefined) =< maps:get(birth, B, undefined) end, ListOfMaps). sort_by_birth(ListOfRecords) > lists:keysort(#item.birth, ListOfRecords). 

29 
Remove ith item from list items.
This will alter the original list or return a new list, depending on which is more idiomatic. Note that in most languages, the smallest valid value for i is 0. 

30 
Launch the concurrent execution of procedure f with parameter i from 1 to 1000.
Tasks are independent and f(i) doesn't return any value. Tasks need not run all at the same time, so you may use a pool. 


31 
Create the recursive function f which returns the factorial of the nonnegative integer i, calculated from f(i1)



32 
Create function exp which calculates (fast) the value x power n.
x and n are nonnegative integers. 
module (int_power). export ([exp/2]). exp (X, N) > exp (X, N, 1). exp (_X, 0, Y) > Y; exp (X, N, Y) when N rem 2 =:= 0 > exp (X * X, N div 2, Y); exp (X, N, Y) > exp (X * X, N div 2, X * Y). 

35 
Implement a function compose (A > C) with parameters f (A > B) and g (B > C), which returns the composition function g ∘ f


36 
Implement a function compose which returns composition function g ∘ f for any functions f and g having exactly 1 parameter.


38 
Find substring t consisting in characters i (included) to j (excluded) of string s.
Character indices start at 0 unless specified otherwise. Make sure that multibyte characters are properly handled. 

39 
Set boolean ok to true if string word is contained in string s as a substring, or to false otherwise.


41 
Create string t containing the same characters as string s, in reverse order.
Original string s must remain unaltered. Each character must be handled correctly regardless its number of bytes in memory. 


43 
Look for a negative value v in 2D integer matrix m. Print it and stop searching.

find_negative_in([]) > undefined; find_negative_in([RowRows]) > find_negative_in(Row, Rows). find_negative_in([], Rows) > find_negative_in(Rows); find_negative_in([PosValues], Rows) when Pos >= 0 > find_negative_in(Values, Rows); find_negative_in([Neg_], _) > Neg. 

44 
Insert the element x at position i in the list s. Further elements must be shifted to the right.



45 
Sleep for 5 seconds in current thread, before proceeding with the next instructions.



46 
Create string t consisting of the 5 first characters of string s.
Make sure that multibyte characters are properly handled. 

47 
Create string t consisting in the 5 last characters of string s.
Make sure that multibyte characters are properly handled. 

48 
Assign to variable s a string literal consisting in several lines of text, including newlines.


49 
Build list chunks consisting in substrings of input string s, separated by one or more space characters.


50 
Write a loop that has no end clause.



51 
Determine whether the map m contains an entry for the key k



53 
Concatenate elements of string list x joined by the separator ", " to create a single string y.



54 
Calculate the sum s of the integer list or array x.



55 
Create the string representation s (in radix 10) of the integer value i.


56 
Forkjoin : launch the concurrent execution of procedure f with parameter i from 1 to 1000.
Tasks are independent and f(i) doesn't return any value. Tasks need not run all at the same time, so you may use a pool. Wait for the completion of the 1000 tasks and then print "Finished". 
run_n_times(Fun, N) > Self = self(), Task = fun (I) > spawn(?MODULE, run_task_and_notify_completion, [Self, Fun, I]) end, lists:foreach(Task, lists:seq(1, N)), wait_for_n_tasks(N). run_task_and_notify_completion(ParentPid, Fun, Arg) > Fun(Arg), ParentPid ! done. wait_for_n_tasks(0) > io:format("Finished~n"); wait_for_n_tasks(N) when N > 0 > receive done > ok end, wait_for_n_tasks(N1). run_n_times(F, 1000). 

57 
Create the list y containing the items from the list x that satisfy the predicate p. Respect the original ordering. Don't modify x inplace.



58 
Create string lines from the content of the file with filename f.


59 
Print the message "x is negative" to standard error (stderr), with integer x value substitution (e.g. "2 is negative").


61 
Assign to the variable d the current date/time value, in the most standard type.


63 
Assign to x2 the value of string x with all occurrences of y replaced by z.
Assume occurrences of y are not overlapping. 


71 
Basic implementation of the Echo program: Print all arguments except the program name, separated by space, followed by newline.
The idiom demonstrates how to skip the first argument if necessary, concatenate arguments as strings, append newline and print it to stdout. 
main() > main(init:get_plain_arguments()). main(ARGV) > io:format("~s~n", [lists:join(" ", ARGV)]). 

75 
Compute the least common multiple x of big integers a and b. Use an integer type able to handle huge numbers.

gcd(A,B) when A == 0; B == 0 > 0; gcd(A,B) when A == B > A; gcd(A,B) when A > B > gcd(AB, B); gcd(A,B) > gcd(A, BA). lcm(A,B) > (A*B) div gcd(A, B). 

76 
Create the string s of integer x written in base 2.
E.g. 13 > "1101" 

78 
Execute a block once, then execute it again as long as boolean condition c is true.



82 
Find how many times string s contains substring t.
Specify if overlapping occurrences are counted. 
countOccurence(List1, List2) > countOccurence(List1, List2, 0). countOccurence(_, [], Count) > Count; countOccurence(List1, [_  Rest] = List2, Count) > case (lists:prefix(List1, List2)) of true > countOccurence(List1, Rest, Count + 1); false > countOccurence(List1, Rest, Count) end. countOccurence("ab", "abcddababa"). 

87 
Exit immediately.
If some extra cleanup work is executed by the program runtime (not by the OS itself), describe it. 

89 
You've detected that the integer value of argument x passed to the current function is invalid. Write the idiomatic way to abort the function execution and signal the problem.


96 
Set boolean b to true if string s starts with prefix prefix, false otherwise.


98 
Convert a timestamp ts (number of seconds in epochtime) to a date with time d. E.g. 0 > 19700101 00:00:00


99 
Assign to the string x the value of the fields (year, month, day) of the date d, in format YYYYMMDD.


100 
Sort elements of arraylike collection items, using a comparator c.



110 
Set the boolean blank to true if the string s is empty, or null, or contains only whitespace ; false otherwise.



116 
Remove all occurrences of string w from string s1, and store the result in s2.



117 
Set n to the number of elements of the list x.


118 
Create the set y from the list x.
x may contain duplicates. y is unordered and has no repeated values. 


119 
Remove duplicates from the list x.
Explain if the original order is preserved. 


124 
Write the function binarySearch which returns the index of an element having the value x in the sorted array a, or 1 if no such element exists.

bsearch([], _) > 1; bsearch([H_T], X) when X < H > 1; bsearch(List, X) > bsearch(List, X, 0, length(List)). bsearch(_List, _X, First, Last) when Last < First > 1; bsearch(List, X, First, Last) > Middle = First + (Last  First) div 2, Item = lists:nth(Middle, List), case Item of X > Middle; _Less when X < Item > bsearch(List, X, First, Middle); _More > bsearch(List, X, Middle + 1, Last) end. 

125 
measure the duration t, in nanoseconds, of a call to the function foo. Print this duration.


131 
Execute f1 if condition c1 is true, or else f2 if condition c2 is true, or else f3 if condition c3 is true.
Don't evaluate a condition when a previous condition was true. 


133 
Set boolean ok to true if string word is contained in string s as a substring, even if the case doesn't match, or to false otherwise.


134 
Declare and initialize a new list items, containing 3 elements a, b, c.



137 
Set the boolean b to true if the string s contains only characters in the range '0'..'9', false otherwise.



142 
Assign to string s the hexadecimal representation (base 16) of integer x.
E.g. 999 > "3e7" 


150 
Remove the last character from the string p, if this character is a forward slash /


152 
Create string s containing only the character c.


157 
Initialize a constant planet with string value "Earth".



165 
Assign to the variable x the last element of the list items.



166 
Create the list ab containing all the elements of the list a, followed by all the elements of the list b.



169 
Assign to the integer n the number of characters of the string s.
Make sure that multibyte characters are properly handled. n can be different from the number of bytes of s. 


175 
From array a of n bytes, build the equivalent hex string s of 2n digits.
Each byte (256 possible values) is encoded as two hexadecimal characters (16 possible values per digit). 

178 
Set boolean b to true if if the point with coordinates (x,y) is inside the rectangle with coordinates (x1,y1,x2,y2) , or to false otherwise.
Describe if the edges are considered to be inside the rectangle. 

186 
Exit a program cleanly indicating no error to OS


205 
Read an environment variable with the name "FOO" and assign it to the string variable foo. If it does not exist or if the system does not support environment variables, assign a value of "none".



213 
Compare four strings in pairwise variations. The string comparison can be implemented with an equality test or a containment test, must be caseinsensitive and must apply Unicode casefolding.

code (C) when $a =< C andalso C =< $z > C  $a; code (C) when $A =< C andalso C =< $Z > C  $A; code(C) > C. isSame([C  Rest1], [C  Rest2]) when is_integer(C)> isSame(Rest1, Rest2); isSame([C1  Rest1], [C2  Rest2]) > case (code(C1)  code(C2)) of 0 > isSame(Rest1, Rest2); _ > false end; isSame([], []) > true; isSame(_, _) > false. Alternative implementation:
code (C) when $a =< C andalso C =< $z > C  $a; code (C) when $A =< C andalso C =< $Z > C  $A; code(C) > C. isSame([C  Rest1], [C  Rest2]) when is_integer(C)> isSame(Rest1, Rest2); isSame([C1  Rest1], [C2  Rest2]) > (code(C1) == code(C2)) andalso isSame(Rest1, Rest2); isSame([], []) > true; isSame(_, _) > false. 

218 
Create the list c containing all unique elements that are contained in both lists a and b.
c should not contain any duplicates, even if a and b do. The order of c doesn't matter. 

219 
Create the string t from the value of string s with each sequence of spaces replaced by a single space.
Explain if only the space characters will be replaced, or the other whitespaces as well: tabs, newlines. 
singleSpace(Text) > singleSpace(0, Text). singleSpace(_, []) > []; singleSpace(32, [32  Rest]) > singleSpace(32, Rest); singleSpace(32, [Ch  Rest]) > [Ch] ++ singleSpace(Ch, Rest); singleSpace(Last, [Ch  Rest]) > [Ch] ++ singleSpace(Ch, Rest). %%singleSpace("this is a text with multiple spaces"). 

237 
Assign to c the result of (a xor b)


249 
Define variables a, b and c in a concise way.
Explain if they need to have the same type. 

251 
Extract integer value i from its binary string representation s (in radix 2)
E.g. "1101" > 13 

252 
Assign to the variable x the value "a" if calling the function condition returns true, or the value "b" otherwise.


254 
Replace all exact occurrences of "foo" with "bar" in the string list x


262 
Assign to t the number of trailing 0 bits in the binary representation of the integer n.
E.g. for n=112, n is 1110000 in base 2 ⇒ t=4 

265 
Set the integer variable i to 42 and calculate its parity (i.e. 0 if it contains an even number of bits, 1 if it contains an odd number of bits).


266 
Assign to the string s the value of the string v repeated n times, and write it out.
E.g. v="abc", n=5 ⇒ s="abcabcabcabcabc" 


269 
Given the enumerated type t with 3 possible values: bike, car, horse.
Set the enum value e to one of the allowed values of t. Set the string s to hold the string representation of e (so, not the ordinal value). Print s. 

274 
Create the string t from the string s, removing all the spaces, newlines, tabulations, etc.
