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Fortran  

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


6 
Do something with each item x of the list (or array) items, regardless indexes.


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


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. 

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.


16 
Call a function f on every node of binary tree bt, in depthfirst infix order



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.


18 
Call a function f on every node of a tree, in depthfirst prefix order



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. 

21 
Swap the values of the variables a and b


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)


25 
Share the string value "Alan" with an existing running process which will then display "Hello, Alan"


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.


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. 

33 
Assign to the variable x the new value f(x), making sure that no other thread may modify x between the read and the write.


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 the boolean ok to true if the 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. 

42 
Print each item v of list a which is not contained in list b.
For this, write an outer loop to iterate on a and an inner loop to iterate on b. 

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


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 the string t consisting of the 5 first characters of the 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 the string s, separated by one or more space characters.



50 
Write a loop that has no end clause.


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". 

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 the 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").


60 
Assign to x the string value of the first command line parameter, after the program name.



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


62 
Set i to the first position of string y inside string x, if exists.
Specify if i should be regarded as a character index or as a byte index. Explain the behavior when y is not contained in x. 

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

65 
From the real value x in [0,1], create its percentage string representation s with one digit after decimal point. E.g. 0.15625 > "15.6%"


67 
Calculate binom(n, k) = n! / (k! * (nk)!). Use an integer type able to handle huge numbers.


69 
Use seed s to initialize a random generator.
If s is constant, the generator output will be the same each time the program runs. If s is based on the current value of the system clock, the generator output will be different each time. 

70 
Get the current datetime and provide it as a seed to a random generator. The generator sequence will be different at each run.


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. 


74 
Compute the greatest common divisor x of big integers a and b. Use an integer type able to handle huge numbers.



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

77 
Declare a complex x and initialize it with value (3i  2). Then multiply it by i.


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


79 
Declare the floating point number y and initialize it with the value of the integer x .


80 
Declare integer y and initialize it with the value of floating point number x . Ignore noninteger digits of x .
Make sure to truncate towards zero: a negative x must yield the closest greater integer (not lesser). 

81 
Declare the integer y and initialize it with the rounded value of the floating point number x .
Ties (when the fractional part of x is exactly .5) must be rounded up (to positive infinity). 

82 
Find how many times string s contains substring t.
Specify if overlapping occurrences are counted. 

84 
Count number c of 1s in the integer i in base 2.
E.g. i=6 → c=2 


85 
Write boolean function addingWillOverflow which takes two integers x, y and return true if (x+y) overflows.
An overflow may be above the max positive value, or below the min negative value. 

86 
Write the boolean function multiplyWillOverflow which takes two integers x, y and returns true if (x*y) overflows.
An overflow may reach above the max positive value, or below the min negative value. 

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

88 
Create a new bytes buffer buf of size 1,000,000.


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.


90 
Expose a readonly integer x to the outside world while being writable inside a structure or a class Foo.


93 
Implement the procedure control which receives one parameter f, and runs f.


95 
Assign to variable x the length (number of bytes) of the local file at path.



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


97 
Set boolean b to true if string s ends with string suffix, false otherwise.


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


105 
Assign to the string s the name of the currently executing program (but not its full path).



106 
Assign to string dir the path of the working directory.
(This is not necessarily the folder containing the executable itself) 


108 
Print the value of variable x, but only if x has been declared in this program.
This makes sense in some languages, not all of them. (Null values are not the point, rather the very existence of the variable.) 

109 
Set n to the number of bytes of a variable t (of type T).



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


111 
From current process, run program x with commandline parameters "a", "b".


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.


120 
Read an integer value from the standard input into the variable n


122 
Create an enumerated type Suit with 4 possible values SPADES, HEARTS, DIAMONDS, CLUBS.


123 
Verify that predicate isConsistent returns true, otherwise report assertion violation.
Explain if the assertion is executed even in production environment or not. 

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.


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



126 
Write a function foo that returns a string and a boolean value.


127 
Import the source code for the function foo body from a file "foobody.txt".


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. 

132 
Run the procedure f, and return the duration of the execution of f.


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.


135 
Remove at most 1 item from list items, having the value x.
This will alter the original list or return a new list, depending on which is more idiomatic. If there are several occurrences of x in items, remove only one of them. If x is absent, keep items unchanged. 

136 
Remove all occurrences of the value x from list items.
This will alter the original list or return a new list, depending on which is more idiomatic. 

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


138 
Create a new temporary file on the filesystem.


141 
Iterate in sequence over the elements of the list items1 then items2. For each iteration print the element.


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

143 
Iterate alternatively over the elements of the lists items1 and items2. For each iteration, print the element.
Explain what happens if items1 and items2 have different size. 

144 
Set boolean b to true if file at path fp exists on filesystem; false otherwise.
Beware that you should never do this and then in the next instruction assume the result is still valid, this is a race condition on any multitasking OS. 

145 
Print message msg, prepended by current date and time.
Explain what behavior is idiomatic: to stdout or stderr, and what the date format is. 

146 
Extract floating point value f from its string representation s


147 
Create string t from string s, keeping only ASCII characters


148 
Read a list of integer numbers from the standard input, until EOF.


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.


153 
Create the string t as the concatenation of the string s and the integer i.


154 
Find color c, the average between colors c1, c2.
c, c1, c2 are strings of hex color codes: 7 chars, beginning with a number sign # . Assume linear computations, ignore gamma corrections. 

155 
Delete from filesystem the file having path filepath.


156 
Assign to the string s the value of the integer i in 3 decimal digits. Pad with zeros if i < 100. Keep all digits if i ≥ 1000.


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


158 
Create a new list y from randomly picking exactly k elements from list x.
It is assumed that x has at least k elements. Each element must have same probability to be picked. Each element from x must be picked at most once. Explain if the original ordering is preserved or not. 


159 
Define a Trie data structure, where entries have an associated value.
(Not all nodes are entries) 

160 
Execute f32() if platform is 32bit, or f64() if platform is 64bit.
This can be either a compiletime condition (depending on target) or a runtime detection. 

161 
Multiply all the elements of the list elements by a constant c


162 
execute bat if b is a program option and fox if f is a program option.



163 
Print all the list elements, two by two, assuming list length is even.


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.


167 
Create the string t consisting of the string s with its prefix p removed (if s starts with p).



168 
Create string t consisting of string s with its suffix w removed (if s ends with w).


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. 

171 
Append the element x to the list s.


175 
From the 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). 

176 
From hex string s of 2n digits, build the equivalent array a of n bytes.
Each pair of hexadecimal characters (16 possible values per digit) is decoded into one byte (256 possible values). 

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. 

179 
Return the center c of the rectangle with coördinates(x1,y1,x2,y2)


182 
Output the source of the current program. A quine is a computer program that takes no input and produces a copy of its own source code as its only output.
Reading the source file from disk is cheating. 

186 
Exit a program cleanly indicating no error to OS


188 
Perform matrix multiplication of a real matrix a with nx rows and ny columns, a real matrix b with ny rows and nz columns and assign the value to a real matrix c with nx rows and nz columns.


189 
Produce a new list y containing the result of the function T applied to all elements e of the list x that match the predicate P.


190 
Declare an external C function with the prototype
void foo(double *a, int n); and call it, passing an array (or a list) of size 10 to a and 10 to n. Use only standard features of your language. 

191 
Given a onedimensional array a, check if any value is larger than x, and execute the procedure f if that is the case



192 
Declare a real variable a with at least 20 digits; if the type does not exist, issue an error at compile time.


193 
Declare two twodimensional arrays a and b of dimension n*m and m*n, respectively. Assign to b the transpose of a (i.e. the value with index interchange).



194 
Given an array a, set b to an array which has the values of a along its second dimension shifted by n. Elements shifted out should come back at the other end.



195 
Pass an array a of real numbers to the procedure (resp. function) foo. Output the size of the array, and the sum of all its elements when each element is multiplied with the array indices i and j (assuming they start from one).


196 
Given an integer array a of size n, pass the first, third, fifth and seventh, ... up to the m th element to a routine foo which sets all these elements to 42.


198 
Abort program execution with error condition x (where x is an integer value)


200 
Compute the hypotenuse h of the triangle where the sides adjacent to the square angle have lengths x and y.


201 
Calculate n, the Euclidean norm of data (an array or list of floating point values).



202 
Calculate the sum of squares s of data, an array of floating point values.


203 
Calculate the mean m and the standard deviation s of the list of floating point values data.


204 
Given a real number a, print the fractional part and the exponent of the internal representation of that number. For 3.14, this should print (approximately)
0.785 2 

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".


206 
Execute different procedures foo, bar, baz and barfl if the string str contains the name of the respective procedure. Do it in a way natural to the language.


207 
Allocate a list a containing n elements (n assumed to be too large for a stack) that is automatically deallocated when the program exits the scope it is declared in.


208 
Given the arrays a,b,c,d of equal length and the scalar e, calculate a = e*(a+b*c+cos(d)).
Store the results in a. 

209 
Declare a type t which contains a string s and an integer array n with variable size, and allocate a variable v of type t. Allocate v.s and v.n and set them to the values "Hello, world!" for s and [1,4,9,16,25], respectively. Deallocate v, automatically deallocating v.s and v.n (no memory leaks).


210 
Assign, at runtime, the compiler version and the options the program was compilerd with to variables version and options, respectively, and print them. For interpreted languages, substitute the version of the interpreter.
Example output: GCC version 10.0.0 20190914 (experimental) mtune=generic march=x8664 

214 
Append extra character c at the end of string s to make sure its length is at least m.
The length is the number of characters, not the number of bytes. 

215 
Prepend extra character c at the beginning of string s to make sure its length is at least m.
The length is the number of characters, not the number of bytes. 

216 
Add the extra character c at the beginning and ending of string s to make sure its length is at least m.
After the padding the original content of s should be at the center of the result. The length is the number of characters, not the number of bytes. E.g. with s="abcd", m=10 and c="X" the result should be "XXXabcdXXX". 

222 
Set i to the first index in list items at which the element x can be found, or 1 if items does not contain x.


223 
Loop through list items checking a condition. Do something else if no matches are found.
A typical use case is looping through a series of containers looking for one that matches a condition. If found, an item is inserted; otherwise, a new container is created. These are mostly used as an inner nested loop, and in a location where refactoring inner logic into a separate function reduces clarity. 

224 
Insert the element x at the beginning of the list items.


225 
Declare an optional integer argument x to procedure f, printing out "Present" and its value if it is present, "Not present" otherwise


226 
Remove the last element from the list items.


227 
Create the new list y containing the same elements as the list x.
Subsequent modifications of y must not affect x (except for the contents referenced by the elements themselves if they contain pointers). 

228 
Copy the file at path src to dst.



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


238 
Write in a new byte array c the xor result of byte arrays a and b.
a and b have the same size. 

243 
Print the contents of the list or array a on the standard output.


247 
Remove all the elements from list x that don't satisfy the predicate p, without allocating a new list.
Keep all the elements that do satisfy p. For languages that don't have mutable lists, refer to idiom #57 instead. 

248 
Construct the "double precision" (64bit) floating point number d from the mantissa m, the exponent e and the sign flag s (true means the sign is negative).


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 string 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


256 
Print the numbers 5, 4, ..., 0 (included), one line per number.


257 
Print each index i and value x from the list items, from the last down to the first.


258 
Convert the string values from list a into a list of integers b.


260 
Declare a new list items of string elements, containing zero elements


261 
Assign to the string x the value of fields (hours, minutes, seconds) of the date d, in format HH:MM:SS.


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 


263 
Write two functions log2d and log2u, which calculate the binary logarithm of their argument n rounded down and up, respectively. n is assumed to be positive. Print the result of these functions for numbers from 1 to 12.



264 
Pass a twodimensional integer array a to a procedure foo and print the size of the array in each dimension. Do not pass the bounds manually. Call the procedure with a twodimensional array.


265 
Calculate the parity p of the integer variable i : 0 if it contains an even number of bits set, 1 if it contains an odd number of bits set.


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" 

267 
Declare an argument x to a procedure foo that can be of any type. If the type of the argument is a string, print it, otherwise print "Nothing."
Test by passing "Hello, world!" and 42 to the procedure. 

268 
Define a type vector containing three floating point numbers x, y, and z. Write a userdefined operator x that calculates the cross product of two vectors a and b.



270 
Given a floating point number r1 classify it as follows:
If it is a signaling NaN, print "This is a signaling NaN." If it is a quiet NaN, print "This s a quiet NaN." If it is not a NaN, print "This is a number." 


271 
If a variable x passed to procedure tst is of type foo, print "Same type." If it is of a type that extends foo, print "Extends type." If it is neither, print "Not related."


272 
Fizz buzz is a children's counting game, and a trivial programming task used to affirm that a programmer knows the basics of a language: loops, conditions and I/O.
The typical fizz buzz game is to count from 1 to 100, saying each number in turn. When the number is divisible by 3, instead say "Fizz". When the number is divisible by 5, instead say "Buzz". When the number is divisible by both 3 and 5, say "FizzBuzz" 


275 
From the string s consisting of 8n binary digit characters ('0' or '1'), build the equivalent array a of n bytes.
Each chunk of 8 binary digits (2 possible values per digit) is decoded into one byte (256 possible values). 

277 
Remove the element e from the set x.
Explains what happens if e was already absent from x. 

280 
Remove all the elements from the map m that don't satisfy the predicate p.
Keep all the elements that do satisfy p. Explain if the filtering happens inplace, i.e. if m is reused or if a new map is created. 

284 
Create a new list a (or array, or slice) of size n, where all elements are integers initialized with the value 0.


285 
Given two floating point variables a and b, set a to a to a quiet NaN and b to a signalling NaN. Use standard features of the language only, without invoking undefined behavior.


286 
Print a line "Char i is c" for each character c of the string s, where i is the character index of c in s (not the byte index).
Make sure that multibyte characters are properly handled, and count for a single character. 

288 
Set the boolean b to true if the set x contains the element e, false otherwise.


289 
Create the string s by concatenating the strings a and b.


291 
Delete all the elements from index i (included) to index j (excluded) from the list items.


292 
Write "Hello World and 你好" to standard output in UTF8.


294 
Given an array a containing the three values 1, 12, 42, print out
"1, 12, 42" with a comma and a space after each integer except the last one. 

296 
Assign to x2 the value of string x with the last occurrence of y replaced by z.
If y is not contained in x, then x2 has the same value as x. 

299 
Write a line of comments.
This line will not be compiled or executed. 

301 
Compute the Fibonacci sequence of n numbers using recursion.
Note that naive recursion is extremely inefficient for this task. 

302 
Given the integer x = 8, assign to the string s the value "Our sun has 8 planets", where the number 8 was evaluated from x.


303 
Declare an array a of integers with six elements, where the first index is 42 and consecutive elements have the indices 43, 44, 45, 46, 47.


305 
Compute and print a^b, and a^n, where a and b are floating point numbers and n is an integer.


309 
Create the new 2dimensional array y containing a copy of the elements of the 2dimensional array x.
x and y must not share memory. Subsequent modifications of y must not affect x. 

310 
Fill the byte array a with randomly generated bytes.


312 
Set b to true if the lists p and q have the same size and the same elements, false otherwise.


314 
Set all the elements in the array x to the same value v


316 
Determine the number c of elements in the list x that satisfy the predicate p.


321 
Assign to c the value of the ith character of the string s.
Make sure to properly handle multibyte characters. i is the character index, which may not be equal to the byte index. 

336 
Compute x = b ⁿ
b raised to the power of n is equal to the product of n terms b × b × ... × b 