Spell out the Revu'a

Question

Actually not inspired neither by Atbash Self Palindromes nor by Generalized Gematria Calculator.

Given a string s of length n, output the Revu'a sequence, which is the first character of s, the first two characters of s, ... the first n–2 characters of s, the first n–1 characters of s, the entire s.

The string will only consist of Unicode (any encoding you want) characters that have strong directionality and are found in the range 0x0000 through 0xFFFF. However, no directionality control characters will occur. All characters in any given string will have the same directionality.

You may return in array notation ["t","te","tes","test"], as a space-separated string "t te tes test", as multi-line text
t
te
tes
test
, a pre-formatted array

t
te
tes
test

, or anything similar. Amounts of leading, separating, and trailing spacing is not important, and neither are trailing newline. Ask if in doubt.

Right-to-Left input must result in Right-to-Left output in proper order:
Input: "נחמן"
Output: "נ נח נחמ נחמן" or

נ
נח
נחמ
נחמן

, or ["נ","נח","נחמ","נחמן"]. Among invalid results are "נחמן נחמ נח נ" ,"ן מן חמן נחמן", and "נחמן חמן מן ן".

Answer 1

05AB1E, 1 byte

η

Builtins ftw ¯\_(ツ)_/¯

Outputs as a list of prefixes.

Try it online or verify all test cases.

Explanation:

η  # Push a list of prefixes of the (implicit) input-string
   # (and output this list implicitly as result)

Answer 2

Dyalog APL, 2 bytes

,\

Cumulative reduce by concatenate. Try it here.

The formatting of the output is nicer when you prefix a ⍕, but it clearly shows the correct order without.

Answer 3

JavaScript (ES6), 27 26 25 bytes

Saved one byte thanks to @nicael and @MartinBüttner, one thanks to @Neil

x=>x.replace(/.?/g,"$` ")

Takes advantage of some built-in features of JS's .replace function. Specifically, in the replacement, $` becomes everything preceding the matched character. Using the regex /.?/g rather than /./g means it also matches the empty string at the end.

Answer 4

Japt, 10 4 bytes

I didn't realize that a cumulative reduce would be so useful in this case. :-)

UŒ+

Outputs as an array, comma-separated by default. If this is not allowed, use this 6-byte code instead:

U¬å+ ·

Try it online!

How it works

      // Implicit: U = input string
U¬    // Split U into chars.
  å+  // Cumulative reduce: loop through each item in the array, concatenating it to the total.
      // ["t","e","s","t"] => ["t","te","tes","test"].
      // Implicit: output last expression

Answer 5

Retina, 11 7 bytes

.
 $`$0

Output is space-separated, with a leading space and a trailing linefeed.

Try it online!

Answer 6

Brainfuck, 40 bytes

My console doesn't support Right-to-Left characters, but I don't think it will work :c

++++++++++>,[>,]<[<]>[[<+>-]<[<]>[.>]>]

Ungolfed:

++++++++++> # Store 10 (Newline)
,[>,]       # Store input
<[<]>       # Goto first character
[           # While next character
  [<+>-]    # Copy character to the left
  <[<]>     # Goto first character
  [.>]      # Print all charaters
  >         # Go to next character
]

Answer 7

Prolog (SWI), 60 49 bytes

Code:

p(X):-findall(S,atom_prefix(X,S),[_|R]),write(R).

Explained:

atom_prefix with X set to input and S as a variable gives 1 prefix of the atom X starting with the empty atom.

findall gets all solutions and puts them in a list.

[_|R] throws away the head (the empty atom) and stores the tail in R

Examples:

p('נחמן').
[נ, נח, נחמ, נחמן]

p('test').
[t, te, tes, test]

Try it online here

Edit: saved 11 bytes by only storing the tail in R.

Answer 8

Python, 35

f=lambda s:f(s[:-1])+[s]if s else[]

Couldn't find a way to use and/or to simplify the recursion because [] is falsy.

Recursive solution, returns a list of strings.

Try it online

Answer 9

Pyth, 3

._z

Prefix builtin does the trick.

Test Suite

Answer 10

GNU Sed, 21

Score includes +1 for -E option to sed:

:
s/^(\S+)\S/\1 &/
t

Works for LTR, but not RTL - I missed that bit.. Actually it does work, the RTL was just not rendering correctly in my terminal. It works fine with IO viewed in a sensible text editor (e.g. emacs). It also works in Ideone:

Try it online.

Answer 11

Brachylog, 5 bytes (Non-competing)

@[@w\

Try it online!

Explanation

@[       Take a prefix of the input
  @w     Write this prefix to STDOUT followed by a linebreak
    \    False: try another prefix

Right-to-left strings seem to work properly, even though I never even considered them.

Answer 12

CJam, 9 bytes

l{N2$@+}*

Output is linefeed-separated.

Test it here.

Explanation

l     e# Read input.
{     e# Fold this block over the input, which is effectively a foreach-loop which skips
      e# the first character...
  N   e#   Push a linefeed.
  2$  e#   Copy the previous string.
  @   e#   Pull up the current character.
  +   e#   Concatenate.
}*

Answer 13

JavaScript, 36 bytes

x=>[...x].map((c,i)=>x.slice(0,i+1))

Demo:

a=x=>[...x].map((c,i)=>x.slice(0,i+1));
document.write(
  a("test")+"<br>"+
  a("נחמן")
)

The principle is to map and output the slice of string from the first char to the every char in the word. Surprisingly, this works perfectly for the RTL strings too, no optimization needed.

Answer 14

TI-BASIC, 18 bytes

For(X,1,10^(9
Disp sub(Ans,1,X
End

Not technically valid: TI-BASIC doesn't support Unicode.

Name this prgmA, and input using Ans.

Program recursion would be shorter, but there would be no way to initialize the variables. Therefore, we display a substring of the input at each iteration. The input is never overwritten, since Disp doesn't return a value.

Eventually, the program terminates with an error after printing the whole string.

Answer 15

My console doesn't support Right-to-Left characters, but I don't think it will work :c

C, 74 bytes (2nd entry)

char m[2<<9];i;main(){do{m[i]=getchar();printf("%s ",m);}while(m[i++]>0);}

Ungolfed:

#include <stdio.h>

// char, because `printf("%s", str);` expects a array of characters.
char str[2<<9];
int  str_len = 0;
int main(void) {
    do {
        str[str_len]=getchar();
        printf("%s ", str);
    } while(m[i++]>0);
    return 0;
}

Answer 16

My console doesn't support Right-to-Left characters, but I don't think it will work :c

C, 105 bytes (3th entry)

m[2<<9];i;j;k;main(){while((m[i++]=getchar())<0);for(;j<i;j++,putchar(10))for(k=0;k<j;k++)putchar(m[k]);}

Ungolfed:

#include <stdio.h>

int str[2<<9];
int str_len = 0;
int main(void) {
    do {
        str[str_len] = getchar();
    } while(str[str_len++] != EOF);
    int i;
    for(i=0; i<str_len; i++) {
        int j;
        for(j=0; j<i; j++) {
          putchar(str[j]);
        }
        putchar(10);
    }
}

Answer 17

Python, 54 Bytes

b='';y=input()
for a in range(len(y)):b+=y[a];print(b)

Answer 18

Java 8, 95 92 58 bytes

s->{for(int i=0;;)System.out.println(s.substring(0,++i));}

Try it online.

Explanation:

s->{                        // Method with String parameter and no return-type
  for(int i=0;              //  Index-integer, starting at 0
      ;)                    //  Loop indefinitely:
    System.out.println(     //   Print with trailing newline:
      s.substring(0,++i     //    Increase the index by 1 first with `++i`
                       ));} //    And print an input-substring in the range [0,i)

Stops the infinite loop with a StringIndexOutOfBoundsException after everything has been printed to STDOUT already, which is allowed according to the meta.

Answer 19

MATL, 8 bytes

Uses current version (8.0.0) of language/compiler

jtn1X"YR

Example

>> matl
 > jtn1X"YR
 >
> test
t
te
tes
test

Explanation

j           % input string
tn          % duplicate and get length, say "N"
1X"         % repeat string N times vertically. Gives a char matrix
YR          % lower triangular part of matrix. Implicitly print

Answer 20

Mathematica, 29 bytes

#<>#2&~FoldList~Characters@#&

TODO: explanation

Answer 21

, 7 chars / 16 bytes

ᴉⓜᵖ ᵴ˖$

Try it here (Firefox only).

There's probably a builtin for this somewhere - I just haven't found it.

Explanation

ᴉⓜᵖ ᵴ˖$ // implicit: ᴉ=split input, ᵴ=empty string
ᴉⓜ      // map over ᴉ
   ᵖ ᵴ˖$ // push ᵴ+=(mapped item char)
         // implicit stack output, separated by newlines

Answer 22

Javascript ES6, 29 bytes

(a,b='')=>[...a].map(x=>b+=x)

This ain't winning anything, but it's a simple solution.

Answer 23

Pyth, 11 Bytes

Vlz=k+k@zNk

Try It Out

Explanation

(z=input)
(k="")
V        for N in Range(
lz       length of z):
=k+k@zN     k=k+z[N]
k           print(k)

Answer 24

Python, 32 bytes

f=lambda s:s and f(s[:-1])+" "+s

Recursive function that outputs a space-separated string with a leading space.

A 34-byte program (Python 2):

s=""
for c in input():s+=c;print s

Answer 25

V, 5 bytes (non-competing)

òÄ$xh

Try it online!

This language is newer than the challenge, making this answer non-competing. Explanation:

ò       " Recursively:
 Ä      "   Duplicate this line
  $     "   Move to the end of this line
   x    "   Delete one character
    h   "   Move one character to the right, which will throw an error when the line is one character long

Answer 26

PowerShell v2+, 28 bytes

[char[]]$args[0]|%{($o+=$_)}

Takes input $args[0], casts it as a char-array, pipes the characters into a loop |%{...}. Each iteration, we accumulate onto $o via += the current character $_. That expression is encapsulated in parens so a copy is placed on the pipeline. At end of execution, the pipeline is flushed via Write-Output which puts a newline between elements.

PS C:\Tools\Scripts\golfing> .\spell-out-the-revua "נחמן"
נ
נח
נחמ
נחמן

PS C:\Tools\Scripts\golfing> .\spell-out-the-revua "PPCG"
P
PP
PPC
PPCG

Answer 27

PHP, 59 Bytes

for(;$i++<mb_strlen($argn);)echo"\n".mb_substr($argn,0,$i);

Online Version

Answer 28

Unwanted, Unnecessary, Opportunistic, 9 bytes

E<+S0;*P 

Answer 29

.+?, 18 bytes

^((.+).)
\2\n\1
$

Explanation

^((.+).)   Replace the first line with
\2         The first line missing the last character
  \n       A newline
    \1     The first line
$          Repeat until the regex doesn't match (when first line has 1 character)

Try it online! (The second command line argument is input)

Answer 30

Burlesque, 2 bytes

iT

Try it online!

iT # Generate inits

Answer 31

GolfScript, 10 bytes

Courtesy to a'_' for saving two bytes by removing redundant bits!

:i,,{)i<}/

Nice short and cute response :)

:i,,{)i>}% #Revu'a Sequence
:i           #Remember the input as i
  ,,         #Array from 0 to i-1
    {   }% #Block, for each element, map this
    {)  }% #Increment the number by 1
    { i }% #Move i to the top of the stack
    {  >}% #Print the characters less than the index i

Try it online!