Using index of to search for multiple characters

Question

In my Arduino project, a string will be received. I understand using .indexof to find the placement of a certain character in the string. My problem is that I need to find the first occurrence of any letter A-Z and haven't found any resources regarding using or statements in an .indexof aka string.indexof("a" || "b" ....).

Is this something that is not possible using indexof functions and if so is there any function that I can use to solve this! Thanks!

Answer 1

Here are two functions that I hope help in your endeavours. You can supply either a String or a char array and you should get the first position of an alpha character. Returns -1 if not present.

See https://www.arduino.cc/reference/en/language/functions/characters/isalpha/

Update:

Thanks to great comments from Edgar & Mat I have updated the functions with best practise and cost improvements.

int alphaPos(const char* str)
{
  for (int i = 0; str[i] !=0 ; ++i) {
    if (isAlpha(str[i]))
    {
      return i;
    }
  }
  
  return -1;
}


int alphaPos(const String& str)
{
  return alphaPos(str.c_str());
}

/*
    Usage:

    String bobble = "&&&88434a";
    int x = alphaPos(bobble);

    if (x != -1) 
    {
      ...x has the position in the string
    }
    else
    {
     ...There is no alpha char present.
    }
*/