Delete element in a slice

Question

func main         a      string  Hello1    Hello2    Hello3       fmt Println a          Hello1 Hello2 Hello3      a   append a  0   a 1           fmt Println a          Hello2 Hello3      How does this delete trick with the append function work   It would seem that it s grabbing everything before the first element  empty array   Then appending everything after the first element  position zero   What does the      dot dot dot  do

User · Answer

There are two options   A  You care about retaining array order   a   append a  i   a i 1          or a   a  i copy a i    a i 1       B  You don t care about retaining order  this is probably faster    a i    a len a -1     Replace it with the last one  CAREFUL only works if you have enough elements  a   a  len a -1       Chop off the last one    See the link to see implications re memory leaks if your array is of pointers   https   github com golang go wiki SliceTricks

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In golang s wiki it show some tricks for slice  including delete an element from slice   Link  enter link description here  For example a is the slice which you want to delete the number i element   a   append a  i   a i 1         OR  a   a  i copy a i    a i 1

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Rather than thinking of the indices in the  a  -    b - and  a b -notations as element indices  think of them as the indices of the gaps around and between the elements  starting with gap indexed 0 before the element indexed as 0     Looking at just the blue numbers  it s much easier to see what is going on   0 3  encloses everything   3 3  is empty and  1 2  would yield   B    Then  a   is just the short version of  a len arrayOrSlice      b  the short version of  0 b  and     the short version of  0 len arrayOrSlice    The latter is commonly used to turn an array into a slice when needed

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I m getting an index out of range error with the accepted answer solution  Reason   When range start  it is not iterate value one by one  it is iterate by index  If you modified a slice while it is in range  it will induce some problem   Old Answer   chars      string  a    a    b    for i  v    range chars       fmt Printf    v   d   s n   chars  i  v      if v     a            chars   append chars  i   chars i 1               fmt Printf    v   chars    Expected     a a b   0  a  a b   0  a  b   0  b Result   b    Actual      Autual  a a b   0  a  a b   1  b  a b   2  b Result   a b    Correct Way  Solution    chars      string  a    a    b    for i    0  i  lt  len chars   i         if chars i      a            chars   append chars  i   chars i 1               i--    form the remove item index to start iterate next item          fmt Printf    v   chars    Source  https   dinolai com notes golang golang-delete-slice-item-in-range-problem html

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Where a is the slice  and i is the index of the element you want to delete   a   append a  i   a i 1             is syntax for variadic arguments in Go   Basically  when defining a function it puts all the arguments that you pass into one slice of that type  By doing that  you can pass as many arguments as you want  for example  fmt Println can take as many arguments as you want    Now  when calling a function      does the opposite  it unpacks a slice and passes them as separate arguments to a variadic function   So what this line does   a   append a  0   a 1         is essentially   a   append a  0   a 1   a 2     Now  you may be wondering  why not just do   a   append a 1         Well  the function definition of append is  func append slice   Type  elems    Type    Type   So the first argument has to be a slice of the correct type  the second argument is the variadic  so we pass in an empty slice  and then unpack the rest of the slice to fill in the arguments

User · Answer

is syntax for variadic arguments   I think it is implemented by the complier using slice    Type   just like the function append    func append slice   Type  elems    Type    Type   when you use  elems   in  append   actually it is a slice   type   So  a   append a  0   a 1        means  a   append a 0 0   a 1      a 0 0  is a slice which has nothing  a 1    is  Hello2 Hello3   This is how it works

[go] Delete element in a slice

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