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Bytes	Lang	Time	Link
014	APLDyalog Unicode	250509T154747Z	Mat_rdv
054	Janet	250508T180519Z	Adam
048	Juby	250508T143655Z	Jordan
011	Pyth	170726T221103Z	Anders K
006	Japt	170723T203134Z	Justin M
091	Java	170725T090249Z	RCB
053	Haskell	170724T162506Z	nimi
013	Brachylog	170724T141221Z	Erik the
006	05AB1E	170724T140049Z	Erik the
058	C++14	170723T215313Z	vaultah
056	Python 3	170723T215106Z	ovs
025	Mathematica	170724T084307Z	user6198
013	CJam	170724T081029Z	Peter Ta
065	Cubix	170724T024159Z	MickyT
032	R	170723T230700Z	MickyT
051	PHP	170723T223234Z	Titus
012	Pyth	170723T220150Z	notjagan
060	Mathematica	170723T212502Z	ZaMoC
038	JavaScript ES6	170723T210113Z	Neil
072	Python	170723T202041Z	Uriel
004	Jelly	170723T204759Z	Leaky Nu
003	Husk	170723T204048Z	Zgarb
006	MATL	170723T202328Z	Luis Men

APL(Dyalog Unicode), 14 bytes ^SBCS

+/2⊥¨⊢⊂⍨1,2≠/,

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1 and ¯1 are used as values.

Explanation

             ,   ravel (vectors stay the same, scalars turn into 1-element vector)
            /    reduce
           ≠     not equal
          2≠/,   2-wise reduce: where the sequence values change
         ,       concatenate
        1,       concatenate 1 with...
       ⍨         reverse order of arguments
      ⊂          partition
     ⊢           the values
     ⊢⊂⍨1,2≠/,  splitting the sequence into parts with identical values
    ¨            each
   ⊥             decode
  2⊥             decode from binary (same as 1+2+4+8+... for positive parts and -1-2-4-8-... for negative parts)
 /               reduce
+/               sum
+/2⊥¨⊢⊂⍨1,2≠/, solution

Janet, 55 54 bytes

|(+;(do(var a 0)(map|(+= a(if(>(* a $)0)a(- $ a)))$)))

J-uby, 48 bytes

Same technique as Anders and Luis.

:slice_when+:!=|:sum+:*%[:first,:+@|:**&2|~:-&1]

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Explanation

:slice_when + :!= | :sum + :* % [:first, :+@ | :** & 2 | ~:- & 1]

:slice_when + :!= |                            # Slice array into runs of equal elements, then
:sum + :* % [      ,                        ]  # Sum products of
             :first                            #   The first element of each run and
                     :+@ | :** & 2 | ~:- & 1   #   2**n-1, where n is the size of the run

Pyth, 11 bytes

s.b*t^2NYr8

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How it works

         r8    run-length encode input
 .b            map (N, Y) ↦
     ^2N           2^N
    t              minus 1
   *    Y          times Y
s              sum

Japt, 8 6 bytes

-2 bytes thanks to @ETHproductions

ò¦ xì2

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Explanation

Implicit input: [1, 1, 1, -1, -1, -1, -1, 1, 1]

ò¦

Partition input array (ò) between different (¦) elements:
[[1, 1, 1], [-1, -1, -1, -1], [1, 1]]

ì2

Map each partition to itself parsed as an array of base-2 digits (ì): [7, -15, 3]

Get the sum (x) of the resulting array: -5

Java, 91 bytes

int f(int[]a){int s=0,r=0,i=-1;while(++i<a.length)r+=s=s!=0&s>0==a[i]>0?2*s:a[i];return r;}

Haskell, 54 53 bytes

k#(a:b:c)=k+last(b:[k*2|a==b])#(b:c)
k#_=k
(#)=<<head

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A simple recursion that either doubles the accumulator k or resets it to 1/-1 and adds the values of each step.

Brachylog, 13 bytes

ḅ⟨{ȧᵐ~ḃ}×h⟩ᵐ+

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Brachylog uses _ instead of -.

Explanation:

?ḅ⟨{ȧᵐ~ḃ}×h⟩ᵐ+. Predicate (implicit ?.)
?               The input
 ḅ              A list where its elements' elements are equal, and when concatenated is ?
            ᵐ   The result of mapping this predicate over ?
  ⟨        ⟩      The result of forking two predicates over ? with a third
   {    }           The result of this predicate on ?
     ᵐ                The result of mapping this predicate over ?
    ȧ                   The absolute value of ?
      ~               An input where the result of this predicate over it is ?
       ḃ                A list that represents the digits of ? in base I (default 2)
          h         An object that is the first element of ?
         ×          A number that is the product of ?
             +  A number that is the sum of ?
              . The output

05AB1E, 6 bytes

γε2β}O

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C++14, 58 bytes

[](auto v,int&s){int p=s=0;for(auto x:v)s+=p=x*p<1?x:2*p;}

Takes input via the v argument (std::vector, or any iterable container), outputs to the s argument (by reference). Each element of v must be either 1 or -1.

Example usage and test cases.

Python 3, 57 56 bytes

-1 byte thanks to @notjagan

f=lambda a,*s,m=1:m*a+(s>()and f(*s,m=(m*2)**(a==s[0])))

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Mathematica, 25 bytes

Tr[Fold[#+##&]/@Split@#]&

CJam (13 bytes)

{e`{(*2b}%1b}

Online test suite. This is an anonymous block (function) which takes an array of ints on the stack and leaves an int on the stack. The last test shows that it handles an empty array correctly, giving 0.

The approach is straightforward run-length encoding followed by a manual run-length decode of each run and base conversion. Using the built-in for run-length decode I get one byte more with {e`1/:e~2fb1b} or {e`{ae~2b}%1b}.

Cubix, 65 bytes

W(?\q.p)w.;0.w;/0>I!U-unP(nwUs;q\^q:;^!u?P(w!u+w.;;>2p!u/@Os..sr\

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        W ( ? \
        q . p )
        w . ; 0
        . w ; /
0 > I ! U - u n P ( n w U s ; q
\ ^ q : ; ^ ! u ? P ( w ! u + w
. ; ; > 2 p ! u / @ O s . . s r
\ . . . . . . . . . . . . . . .
        . . . .
        . . . .
        . . . .
        . . . .

Watch it run

As a brief explanation of this:

Read in each integer (1 or -1) and compare it to previous. If:
- the same push it to the bottom as the start of a counter
- else bring counter to top and increment/decrement it as appropriate.
Once input is finished bring each counter to the top and handling negatives do 2 ^ counter - 1
Sum the results and output

R, 32 bytes

sum((2^(R=rle(scan()))$l-1)*R$v)

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This is the same method as a few others here.

With the input of -1 -1 1 1 -1 -1 -1

Do a Run Length Encoding on the input. Results with lengths of 2, 2, 3 and values -1, 1, -1
Do 2 to power of lengths - 1. Results in 3, 3, 7
Multiply by the RLE values giving -3, 3, -7
Return the sum -7

PHP, 51 bytes

while($d=$argv[++$i])$s+=$x=$d*$x>0?2*$x:$d;echo$s;

Run with -n or try it online.

Pyth, 12 bytes

sm*edt^2hdr8

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Mathematica, 60 bytes

Tr[Last@*Accumulate/@(#[[1]]2^(Range@Tr[1^#]-1)&/@Split@#)]&

JavaScript (ES6), 38 bytes

a=>a.map(e=>r+=d=d*e>0?d+d:e,r=d=0)&&r

Python, 76 72 bytes

f=lambda s,k=1:len(s)and(f(s,s[0])if s[0]*abs(k)/k-1else k+f(s[1:],2*k))

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Jelly, 4 bytes

ŒgḄS

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Husk, 3 bytes

ṁḋg

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Explanation

ṁḋg
  g  Group equal adjacent elements,
ṁ    take sum of
 ḋ   base-2 decoding of each group.

MATL, 6 bytes

Y'Wq*s

Try it online! Or verify all test cases.

Explanation

Consider input [1 1 1 1 1 1 -1 -1 -1 -1 1 1 1].

     % Implicit input
     % STACK: [1 1 1 1 1 1 -1 -1 -1 -1 1 1 1]
Y'   % Run-length encoding
     % STACK: [1 -1 1], [6 4 3]
W    % Exponentiation with base 2, element-wise
     % STACK: [1 -1 1], [64 16 8]
q    % Subtract 1
     % STACK: [1 -1 1], [63 15 7]
*    % Multiply, element-wise
     % STACK: [63 -15 7]
s    % sum of array
     % STACK: 55
     % Implicit display

APL(Dyalog Unicode), 14 bytes SBCS

Explanation

Janet, 55 54 bytes

J-uby, 48 bytes

Explanation

Pyth, 11 bytes

How it works

Japt, 8 6 bytes

Explanation

Java, 91 bytes

Haskell, 54 53 bytes

Brachylog, 13 bytes

05AB1E, 6 bytes

C++14, 58 bytes

Python 3, 57 56 bytes

Mathematica, 25 bytes

CJam (13 bytes)

Cubix, 65 bytes

R, 32 bytes

PHP, 51 bytes

Pyth, 12 bytes

Mathematica, 60 bytes

JavaScript (ES6), 38 bytes

Python, 76 72 bytes

Jelly, 4 bytes

Husk, 3 bytes

Explanation

MATL, 6 bytes

Explanation

APL(Dyalog Unicode), 14 bytes ^SBCS