Evaluate an expression of minus and tilde

Question

Given an expression matching the regex /^[-~]*x$/, evaluate it in terms of x and output a string matching the regex /^-?x[+-]\d+$/.

For example, the string -~x evaluates to x+1, while the string -~-x evaluates to -x+1, and the string -~-~--x evaluates to x+2.

We start from x and evaluate the string right to left. - negates the term, while ~ converts y to -y-1.

Testcases:

    x  x+0
   ~x -x-1
  -~x  x+1
 ~-~x -x-2
-~-~x  x+2
--~~x  x+0
  ~-x  x-1
 -~-x -x+1

This is code-golf. Shortest answer in bytes wins.

The input/output format is strict. The "x" is mandatory.

Answer 1

Python 2, 42 41 39 bytes

lambda s,x=0:'-x%+d'[len(s)%2:]%eval(s)

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Answer 2

Retina, 47 44 bytes

+`--|~~

((~)|-)*x
$&+$#2
T`+`-`^~.*
~
-
--

Try it online! Edit: Saved 3 bytes thanks to @MartinEnder. Expanation:

+`--|~~

Delete pairs of adjacent duplicates.

((~)|-)*x
$&+$#2

Count the number of ~s which gives us the magnitude of the term.

T`+`-`^~.*

If the first character is a ~ then the term should be negative.

~
-
--

If the number of ~s and -s is odd then the x should be negative.

Answer 3

JavaScript, 59 bytes

x=>['-'[x.length&1]]+'x'+['+'[(x=eval(x.join` `))<0^0]]+~~x

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Answer 4

PowerShell Core, 102 bytes

$s=-1
switch -r($args[$args.Count..0]){.{$a=-$a;$s=-$s}~{$a--}}"$s`x+$a"|% *ce '+-','-'|% *ce '1x','x'

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Passes an expression as a string using splatting
Then processes it from right to left
For each char, negate $s and $a, and if the char is ~ , decrement $a
Then concatenate them all: $s + "x+" + $a
Replace +- with -
Remove the useless 1 before x

Answer 5

Perl 5, 75 + 1 (-n)= 76 bytes

map{$y=-$y;$y--if/~/}reverse/-|~/g;printf"%sx%+d",((-1)**y/-~//)=~s/1//r,$y

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Answer 6

C (gcc), 69 bytes

a;s;f(char*p){for(a=s=0;*p;a-=*p++%5*~-s)s^=2;printf("-x%+d"+!!s,a);}

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-1 byte thanks to @ThePirateBay

Answer 7

Ruby, 36 bytes

Port of user48543‘s Python answer.

->s{x=0
"-x%+d"[s.size%2..]%eval(s)}

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Answer 8

><> (Fish), 91 79 bytes

Was producing incorrect output, but for a change fixing this actually saved me bytes.

10>i:'-'=?v:'~'=?vv
 .\r*-10r~<1-@:$~/~
d3/"+"on; .3dv?(0r/
;n^?)-10:o"x"\"-"o/

Try this

Significantly harder to parse in reverse order. Basically produce a expression of the form ax + b

• For a -, set a to -a.
• For a ~, set b to b-a, then re-use the same code to set a to -a.

Rest of the code is printing the solution. Special cases for printing the - in front of x and needing a + if the extra number is not negative.

Answer 9

05AB1E (legacy), 20 bytes

á0:.E…-x+ì„+-¤:IgÉi¦

Port of (deleted) user48543's Python answer.

Try it online or verify all test cases.

Explanation:

á      # Only keep the letters of the (implicit) input (the "x")
 0:    # Replace the "x" in the (implicit) input with "0"
   .E  # Evaluate and execute it as Python code
…-x+ì  # Prepend string "-x+"
„+-¤:  # Replace a potential "+-" with "-"
IgÉi   # If the length of the original input is odd:
    ¦  #  Remove the leading "-"
       # (after which the result is output implicitly)

Answer 10

Java 8, 186 168 167 bytes

s->{s=s.replaceAll("--|~~","");int l,i=s.length()-(l=(s=s.replace("-~","")).length())>>1;return(l-(s=s.replace("~","")).length()>0?"-"+s+~i:s+"+"+i).replace("--","");}

Definitely room for improvements..

-1 byte thanks to @ceilingcat replacing (a-b)/2 with a-b>>1.

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Explanation:

s->{                            // Method with String as both parameter and return-type
  s=s.replaceAll("--|~~","");   //  Remove all "--" and "~~"
  int l,                        //  Temp integer to reduce bytes
      i=s.length()-(l=(s=s.replaceAll("-~","")).length())>>1;
                                //  Remove all "-~" and save count in `i`
  return(l-(s=s.replaceAll("~","")).length()
                                //  Remove all remaining "~"
         >0?                    //  and if its non-empty:
           "-"                  //   Start with a minus sign
           +s                   //   followed by the remaining `s`
           +~i                  //   followed by `-i-1`
          :                     //  Else:
           s                    //   Start with the remaining `s`
           +"+"                 //   followed by a plus sign
           +i                   //   followed by `i`
         ).replaceAll("--","");}//  And then remove all "--"