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Write a piece of code that takes a string as input, and outputs a piece of code in the same language that, when run, will output the initial input string.
It must be able to handle any combination of characters A-Z, a-z, and 0-9.
Example in Python:
import sys
print "print('" + sys.argv[1] + "')"
Given the input of testing123, it will return print('testing123').
Since this is code-golf, the shortest answer in bytes will win.
#
How it works
# //Takes the input and places it onto the string stack
//This is then output implicitly
{input} //The next program then consists of the input string
//This is then placed directly onto the string stack
//Then output implicitly
An alternative, also at 1 byte is:
$
This works the same as the above but only takes the first line of input. Seeing as input will only ever be [A-Za-z0-9] this is fine.
pryr::f(function()cat(x))
which evaluates to the function:
function (x)
function() cat(x)
which returns the function:
function()cat(x)
where x is defined in the scope of the first function, and taken directly from its input.
f=pryr::f(function()print(x)) f('test') function()print(x) <environment: 0x000000000aad19d8> I'm not sure I can actually then run that output code and get the string 'test'. Obviously this answer outputs a function that prints the string, I'm just not sure how literally to interpret the spec.
\$\endgroup\$
x.
\$\endgroup\$
function()cat(x) and get the string, but that's not literally true - I'd have to save that function, and x would have to be saved somewhere ... does this mean that the spec isn't actually requiring "a piece of code that when run...`, and in fact is fine with returning a function that outputs the string?
\$\endgroup\$
function()cat(x) then it won't actually return x - I have to actually invoke the function with x as input. Am I misunderstanding? Being overly literal?
\$\endgroup\$
id
id returns it's argument unchanged.
id "abc" returns "abc" which evaluates to itself, which is a valid output method according to or standard rules. id is polymorphic and works for all kind of input types, so it also works for integer inputs.
The challenge requires to "output a piece of code". As @TannerSwett point out in a comment, the output of id is not valid Haskell source code, but a Haskell value or function that can be evaluated further, so it might also qualify as "code". If "code" means "source code" then we have a 4 byte answer
show
id "abc" really evaluate to the string abc (which would normally be written with quotation marks to indicate that it's a string), rather than to the string literal "abc"? I would think that "interpreting the output of id "abc" as a Haskell expression" would mean interpreting abc, not "abc", as an expression.
\$\endgroup\$
Aug 14, 2017 at 7:34
id is a valid answer. I'll edit this in my answer.
\$\endgroup\$
$0="BEGIN{print\""$0"\"}"
Should work for most input other than ".
If some (possibly empty) input is allowed for the secondary program this could be shortened to:
$0="$0=\""$0"\""
91Pn93PACP
Straightforward: print an open bracket, then the input, then the close bracket and the letter p for the print command. 91Pn23920P also works.
/->:?v";"o;
/l^ >"o''"o{ooo1
Takes input using the -s flag
Prints a program that reads and print the original input character by character.
input -> 'i'o'n'o'p'o'u'o't'o;
function(x)"[[<-"(sys.call(),1,"cat")
How it works:
sys.call (makes only sense if used from within a function) returns the call; the first element of it is the name of the function; this is replaced on-the-fly by cat (which will print its arguments).
A nicer version:
sqk <- function(x)"[[<-"(sys.call(),1,as.name("cat"))
# will print cat(args) instead of "cat"(args) - both are functional but the 2nd is nicer
Example with output:
> sqk("The paws")
cat("The paws")
A rather strange challenge, especially given that the solution is only required to support alphanumeric strings.
s->"v->\""+s+'"'
This is a lambda from a string to the string representation of a lambda taking an empty argument of any type and returning the string.
s->()->s
Function that takes a string, and returns a closure that returns the string when called.
Alternately, a program outputting a program:
print(:(show($(ARGS[1]))))
(Removed, of all things, a trailing whitespace. Smh. Also changed inner print to show.)
INPUT s$
?"?";
WRITE s$
Gets input from the user, and then prints a question mark followed by the input wrapped in double quotes. (Question mark is a shortcut for PRINT.)
Try it online! Takes input surrounded in any of "‘’“” (as long as the first and last quotes are the same).
The program immediately reaches the end, so it triggers implicit output. Since the length of the stack (0) is less than the arity of the print function (1), it implicitly checks if there's input (which there is), and if so uses it as the argument. It outputs with a trailing newline, but that doesn't matter since newlines are nops in 05AB1E.
cat.Finally, each of "‘’“” are used for strings. The difference is that ‘’“” are used for compressed strings while " is regular. However, ‘’“” treat all ASCII characters normally, so they don't make a difference for this challenge. Declaring strings pushes them to the stack, so now the original input is on the stack of the generated program. At the end, it implicitly outputs the top of the stack - which is, you guessed it, the original input.
Say you input "testing123". Since the program is a one-line cat, it outputs "testing123". Running this will push everything between "" to the stack, therefore pushing the string "testing123". Finally, it implicitly outputs the top of the stack, printing testing123.
2x0v1x1f1r3x0v4e2x1v2f0x1x2f1v3x0v3e1s2x1v0m1a1o8m4m3m1a1o2f0x1x3f0m1a1o8m3m5m9s1o2d7s1o3d7m3s1o1f0x1x4f0a0x1f
Works for any null-terminated input string, with some caveats: programs generated for strings containing any control characters between SOH and TAB (values 1-9) will produce incorrect output due to a language quirk, and programs generated for strings containing any control characters between VT and US (values 11-31), or the control character DEL (value 127), will error out with invalid output value if run. Luckily, none of these cases are required by the challenge.
Output programs are generated naïvely and are thus near-irreducible; the output program for an input of ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 will take around 125 milliseconds to generate, but around 10 seconds to run.
Explanation (with 0x commands removed)
2x0v # Set variable 0 equal to 0
1x1f # Function 1
1r # Read a byte of input
3x0v4e # Goto function 4 if it equals variable 0
2x1v # Otherwise, store it in variable 1,
2f # and call function 2
1x2f # Function 2
1v # Set the register equal to the value of variable 1
3x0v3e # Goto function 3 if this equals variable 0
1s2x1v # Otherwise, subtract 1 from variable 1,
0m1a1o8m4m3m1a1o # output "1a",
2f # and jump back to the start of function 2
1x3f # Function 3
0m1a1o8m3m5m9s1o2d7s1o3d7m3s1o # Output "1o0m"
1f # Call function 1
1x4f # Function 4
0a # Add 0 to the register
1f # Call function 1
q because there's a built in for quoting strings
\$\endgroup\$
+Nz
Explaination:
+Nz expects any input
+ joins on same line
N quotation mark
z input as string
"\""<>#<>"\"&"&
Not much.
Defer@Print@#&
For input "test", this function will output Print["test"], which prints "test" when run.
Warning : the code that will be printed will be invalid if input contains at least one of the character "
#include<iostream>
int main(int a,char**v){std::cout<<"#include<iostream>\nint main(){std::cout<<\""<<(a>1?v[1]:"")<<"\";}";}
If empty strings are considered as invalid input :
#include<iostream>
int main(int a,char**v){std::cout<<"#include<iostream>\nint main(){std::cout<<\""<<v[1]<<"\";}";}
./program "", so the second program is equally valid.
\$\endgroup\$
s=>$"()=>\"{s}\""
`,(read-line)
For instance, given the input john, the output will be "john", which evaluates to itself.
For a program that works through printing and not through the REPL:
`(princ,(read-line))
that produces (princ input-string).
i:1+?!v
-1"#"~<.1fo;!?l"<.09o;!?l"r}:
Fairly simple;
Takes input, prints out a printing loop with the string attached to the end.
ì (prepend), since you want a quote at the start of the text, not the end. Also, per meta consensus you're allowed to take input surrounded in quotes, making a 0 byter possible. ;)
\$\endgroup\$
\`^
¶
For an input like testing123 returns the program:
testing123
which in turn produces the desired output.
There might be a trick to disable the newline append with shorter syntax, but I don't know it!
print("print(\"\(CommandLine.arguments[1])\")")
I think this is pretty straight forward.
q`
Explanation:
q e# Input
` e# String representation
'print(%r)'&(%)
Binds 'print(%r)' to the left argument of % string formatting. When the input is given, it is applied as the second (right) argument which formats into the print statement.
