String Manipulation

O2scl

There are a couple classes and functions to help manipulate strings of text found in src/base/string_conv.h.

The columnify class converts a set of strings into nicely formatted columns by padding with the necessary amount of spaces. This class operates on string objects of type std::string, and also works will for formatting columns of floating-point numbers. This class is used to provide output for matrices in the functions o2scl::matrix_out().

The format_float class will reformat double precision numbers into a form appropriate for HTML or LaTeX documents.

A related function, o2scl::screenify(), reformats a column of strings into many columns stored row-by-row in a new string array. It operates very similar to the way the classic Unix command ls organizes files and directories in multiple columns in order to save screen space.

The function o2scl::function_to_double() converts strings like "pi/3.0" and "exp(cos(-1.0e-2))" to double-precision floating point numbers using find_constants and calc_utf8. An alternate version which won’t call the error handler is o2scl::function_to_double_nothrow(). This latter function is the one used by acol -calc. These conversions also work in multiprecision, see Multiprecision Support.

A class kwargs stores a map of strings which can be converted to base C types similar to a Python dictionary.

There are also a set of string conversion functions. They partially duplicate the functionality of C++ Standard Library functions like std::stod() and std::to_string, but often provide alternate forms and different options. These functions include:

• o2scl::btos() - boolean value to string

• o2scl::dtos() - double to string

• o2scl::itos() - integer to string

• o2scl::ptos() - pointer to string

• o2scl::szttos() - size_t to string

• o2scl::stob() - string to boolean value

• o2scl::stod() - string to double (uses std::stod())

• o2scl::stoi() - string to integer (uses std::stoi())

• o2scl::stoszt() - string to size_t

• o2scl::s32tod_nothrow() - char32 string to double which never throws an exception

• o2scl::stod_nothrow() - string to double which never throws an exception

• o2scl::stoi_nothrow() - string to integer which never throws an exception

• o2scl::stoszt_nothrow() - size_t to string which never throws an exception

Other functions in src/base/string_conv.h are:

• o2scl::char32_to_utf8()

• o2scl::count_words()

• o2scl::find_constant()

• o2scl::float_expo_mant()

• o2scl::has_minus_sign()

• o2scl::is_number()

• o2scl::parse_fortran_format()

• o2scl::rewrap()

• o2scl::rewrap_ignore_vt100()

• o2scl::rewrap_keep_endlines()

• o2scl::size_of_exponent()

• o2scl::split_string()

• o2scl::split_string_delim()

• o2scl::string_replace()

• o2scl::string_to_char_array()

• o2scl::string_to_uint_list()

• o2scl::unc_to_string()

• o2scl::utf8_to_char32()

String example

/* Example: ex_string.cpp
   -------------------------------------------------------------------
   Demonstrate the string conversion classes and functions
*/

#include <o2scl/test_mgr.h>
#include <o2scl/format_float.h>
#include <o2scl/misc.h>
#include <o2scl/funct_to_fp.h>

using namespace std;
using namespace o2scl;

int main(void) {
  
  cout.setf(ios::scientific);
  
  test_mgr t;
  t.set_output_level(2);
  
  format_float ff;
  ff.latex_mode();

  cout << "Output a LaTeX table of numbers: " << endl;
  cout << endl;
  cout << "\\begin{table}" << endl;
  cout << "\\begin{tabular}{cc}" << endl;
  cout << "\\hline" << endl;
  cout << "Column 1 & Column 2 \\\\" << endl;
  cout << "\\hline" << endl;
  cout << ff.convert(1.1e-6) << " & " 
       << ff.convert(-4.0) << " \\\\" << endl;
  cout << ff.convert(134.567) << " & " 
       << ff.convert(1568234034) << " \\\\" << endl;
  cout << "\\hline" << endl;
  cout << "\\end{tabular}" << endl;
  cout << "\\end{table}" << endl;
  cout << endl;

  cout << "Function function_to_double():" << endl;
  double x=function_to_double("cyl_bessel_i(2,pi)");
  cout << x << endl;
  t.test_rel(x,2.618495,1.0e-6,"BesselI(2,x)");

  cout << "Function string_to_uint_list():\n  " << endl;
  vector<size_t> ulist;
  string_to_uint_list("1,2-4,6,10-11",ulist);
  vector_out(cout,ulist,true);
  t.test_gen(ulist==vector<size_t>({1,2,3,4,6,10,11}),"uint list");

  t.report();
  return 0;
}