Function: aref

aref is a function defined in data.c.

Signature

(aref ARRAY IDX)

Documentation

Return the element of ARRAY at index IDX.

ARRAY may be a vector, a string, a char-table, a bool-vector, a record, or a byte-code object. IDX starts at 0.

View in manual

Probably introduced at or before Emacs version 20.4.

Aliases

svref (obsolete since 27.1) cl-svref avl-tree--node-branch

Source Code

// Defined in /usr/src/emacs/src/data.c
{
  register EMACS_INT idxval;

  CHECK_FIXNUM (idx);
  idxval = XFIXNUM (idx);
  if (STRINGP (array))
    {
      int c;
      ptrdiff_t idxval_byte;

      if (idxval < 0 || idxval >= SCHARS (array))
	args_out_of_range (array, idx);
      if (! STRING_MULTIBYTE (array))
	return make_fixnum ((unsigned char) SREF (array, idxval));
      idxval_byte = string_char_to_byte (array, idxval);

      c = STRING_CHAR (SDATA (array) + idxval_byte);
      return make_fixnum (c);
    }
  else if (BOOL_VECTOR_P (array))
    {
      if (idxval < 0 || idxval >= bool_vector_size (array))
	args_out_of_range (array, idx);
      return bool_vector_ref (array, idxval);
    }
  else if (CHAR_TABLE_P (array))
    {
      CHECK_CHARACTER (idx);
      return CHAR_TABLE_REF (array, idxval);
    }
  else
    {
      ptrdiff_t size = 0;
      if (VECTORP (array))
	size = ASIZE (array);
      else if (COMPILEDP (array) || RECORDP (array))
	size = PVSIZE (array);
      else
	wrong_type_argument (Qarrayp, array);

      if (idxval < 0 || idxval >= size)
	args_out_of_range (array, idx);
      return AREF (array, idxval);
    }
}