How to append a char to a std string

Question

The following fails with the error prog cpp 5 13  error  invalid conversion from    char    to    const char      int main       char d    d     std  string y  Hello worl      y append d      Line 5 - this fails   std  cout  lt  lt  y    return 0      I also tried  the following  which compiles but behaves randomly at runtime   int main       char d 1       d       std  string y  Hello worl      y append d     std  cout  lt  lt  y    return 0      Sorry for this dumb question  but I ve searched around google  what I could see are just  char array to char ptr    char ptr to char array   etc

User · Answer

To add a char to a std  string var using the append method  you need to use this overload   std  string  append size type  Count  char  Ch    Edit   Your re right I misunderstood the size type parameter  displayed in the context help  This is the number of chars to add  So the correct call is  s append 1  d     not  s append sizeof char   d     Or the simpliest way    s    d

User · Answer

I found a simple way    I needed to tack a char on to a string that was being built on the fly   I needed a char list  because I was giving the user a choice and using that choice in a switch   statement   I simply added another std  string Slist  and set the new string equal to the character   list  - a  b  c or whatever the end user chooses like this   char list  std  string cmd  state    Slist  Slist   list    set this string to the chosen char  cmd   Slist   state x     whatever   system cmd c str       Complexity may be cool but simplicity is cooler  IMHO

User · Answer

str append 10u  d      appends character d 10 times   Notice I have written 10u and not 10 for the number of times I d like to append the character  replace 10 with whatever number

User · Answer

y    d    I would use    operator instead of named functions

User · Answer

Use push back     std  string y  Hello worl    y push back  d   std  cout  lt  lt  y

User · Answer

Try the    operator link text  append   method link text  or push back   method link text  The links in this post also contain examples of how to use the respective APIs

User · Answer

Also adding insert option  as not mentioned yet    std  string str  Hello World    char ch   str push back ch      ch is the character to be added OR str append sizeof ch  ch   OR str insert str length   sizeof ch  ch    not mentioned above

User · Answer

Try using the d as pointer y append  d

User · Answer

I test the several propositions by running them into a large loop  I used microsoft visual studio 2015 as compiler and my processor is an i7  8Hz  2GHz       long start   clock        int a   0        100000000     std  string ret      for  int i   0  i  lt  60000000  i                  ret append 1                  ret                   ret push back                 ret insert ret end    1                  ret resize ret size     1                  long stop   clock        long test   stop - start      return 0    According to this test  results are         operation             time ms             note ------------------------------------------------------------------------ append                     66015                            67328      1 02 time slower than  append  resize                     83867      1 27 time slower than  append  push back  amp  insert         90000      more than 1 36 time slower than  append    Conclusion     seems more understandable  but if you mind about speed  use append

User · Answer

the problem with   std  string y  Hello worl    y push back  d   std  cout  lt  lt  y    is that you have to have the  d  as opposed to using a name of a char  like char d    d   Or am I wrong

User · Answer

If you are using the push back there is no call for the string constructor  Otherwise it will create a string object via casting  then it will add the character in this string to the other string  Too much trouble for a tiny character

User · Answer

In addition to the others mentioned  one of the string constructors take a char and the number of repetitions for that char   So you can use that to append a single char   std  string s    hell   s    std  string 1   o

User · Answer

int main       char d    d     std  string y  Hello worl       y    d    y push back d     y append 1  d     appending the character 1 time   y insert y end    1  d     appending the character 1 time   y resize y size   1  d     appending the character 1 time   y    std  string 1  d     appending the character 1 time     Note that in all of these examples you could have used a character literal directly  y     d     Your second example almost would have worked  for unrelated reasons  char d 1       d    didn t work  but char d 2       d     note the array is size two  would have been worked roughly the same as const char  d    d    and a string literal can be appended  y append d

[c++] How to append a char to a std::string?

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