{fmtextras}

These are my formatter classes for the {fmt} library soon to be std::format

• Table of contents
  • Introduction
    • Licence
  • The std::complex formatter
    • Spec-Usage
  • The colour/style formatters
  • Example code
    • Results of compiling and running

Introduction

There are three formatters so far in this library

1. for std::complex<T>.
2. for fmt::text_style to allow you to introduce a colour/style change anywhere in your format_string.
3. for fmtextras::reset_colour to put the colours etc back after changing using a fmt::text_style argument.

Licence

I'm releasing this under the LGPL version 3 see the LICENCE.md file, or COPYING for plain text

The std::complex formatter

This is my formatter<std::complex<T>, Char> class for the {fmt} library soon to be std::format

Spec-Usage

For std::complex<T> then the format spec is as follows:

replacement_field ::=  "{" [arg_id] [":" cmplx_format_spec] "}"
arg_id            ::=  integer | identifier
integer           ::=  digit+
digit             ::=  "0"..."9"
identifier        ::=  id_start id_continue*
id_start          ::=  "a"..."z" | "A"..."Z" | "_"
id_continue       ::=  id_start | digit

all standard except for cmplx_format_spec which is as follows

cmplx_format_spec     ::= cmplx_form [ format_spec_for_T ]

cmplx_form            ::= [ three_char_cmplx_spec ]

three_char_cmplx_spec ::= [ style_spec ] three_char_cmplx_spec
                          | [ spacing ]  three_char_cmplx_spec
                          | [ bracket ]  three_char_cmplx_spec

style_spec             ::= '$' | ',' | '*' | '|'

spacing                ::= '_' | ';'

bracket                ::= '@' | '~'

where

• $ means expresion style (i.e. num plus_or_minus numi ).
• , means pair style (i.e. (num, num) ).
  • NB: this style overrides brackets i.e. @ as no brackets makes no sense for this style
• * means star style (i.e. num plus_or_minus num *i ), some people like this apperently.
• | means lisp style (i.e. #C(num, num) ), this syle is used in common lisp.
  • NB: this style overrides brackets i.e. @ as no brackets makes no sense for this style
• _ space the , or + or -
• ; don't space , or + or -
• @ don't surround with brackets.
• ~ surround with brackets.

and format_spec_for_T is the format_specifier for the type T.

NB: I only accept 3 chars in the three_char_cmplx_spec.

To compile the the test program testcmplx just run

$ g++ -std=c++20 -o testcmplx testcmplx.cpp -lfmt

or

$ clang++ -std=c++20 -o testcmplx testcmplx.cpp -lfmt

where $ is your prompt or use some sort of make/build system like cmake or what ever.

or

$ cmake -S . -B build # if you have just cloned from git assumming you are in the fmtextras dir

$ CC=gcc CXX=g++ cmake --build ./build --config Release

or

$ CC=clang CXX=clang++ cmake --build ./build --config Release

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The colour-style formatters

There are 2 colour/style formatters

1. for fmt::text_style to allow you to introduce a colour/style change anywhere in your format_string.
2. for fmtextras::reset_colour to put the colours etc back after changing using a fmt::text_style argument.
3. for americans there is fmtexras::reset_color which is an alias to fmtextras::reset_colour.

NB: The colour stuff 1. & 2. can work with the forms of fmt::format and fmt::print and friends but 3. (i.e. fmtextras::reset_colour) is redundant as they do a reset any way at the end of their call, also this works with operator""_format() where as there is no such fuctionality by default.

Also Note: each colour/style change requires a format specifier {} will do and a coresponding argumet of type fmt::text_style, be aware that the formater will ignore anything after the : as I don't need anything.

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Example code

godbolt

#include "complexfmt.h"
#include "colourfmt.h"
#include "fmt/color.h"
#include <ios>
#include <vector>
#include <numeric>
#include <string>
#include <iostream>
#include <fstream>
#include <iomanip>
int main(int argc, char *argv[]){
    using std::complex_literals::operator""i;
    using std::complex_literals::operator""if;
    using std::complex_literals::operator""il;
    using std::literals::string_literals::operator""s;
    using namespace fmt::literals;
    std::complex<double> z = 3.1415926536 + 2.71828182845i;
    std::cout << fmt::format("z == {0:,0.10} == {0:@0.10}\n{1}z {5}=={1} {0:$@;0.10} {3}=={4} {0:,;0.10}{2}\nz == {0:*;0.10} == {0}"s, z,
            fg(fmt::color::green) | bg(fmt::color::red) | fmt::emphasis::bold, fmtextras::reset_colour(),
            fg(fmt::color::blue) | bg(fmt::color::red) | fmt::emphasis::bold,
            fg(fmt::color::yellow) | bg(fmt::color::red) | fmt::emphasis::bold,
            fg(fmt::color::blue) | bg(fmt::color::red) | fmt::emphasis::bold) << std::endl;
    std::cout << fmt::format("z == {:@*0^{}.{}f}", z, 25, 20) << std::endl;
    std::cout << fmt::format("z == {:@ >{}.{}f}", z, 25, 20) << std::endl;
    
    std::complex<double> w = 4.98 - 34.765i;
    std::cout << fmt::format("w == {:{}.{}}", w, 25, 20) << std::endl;
    std::cout << fmt::format("w == {:@*0^{}.{}f}", w, 25, 20) << std::endl;
    std::cout << fmt::format("w == {:@ >{}.{}f}", w, 25, 20) << std::endl;
    std::cout << fmt::format("w == {0:,0.10} == {0:@0.10}\nw == {0:$@;0.10} == {0:,;0.10}\nw == {0:*;0.10} == {0}"s, w) << std::endl;
    std::cout << fmt::format("z == {z:,{width}.{precis}}", "z"_a=z, "width"_a=25, "precis"_a=20) << std::endl;
    std::cout << fmt::format(fg(fmt::color::green) | bg(fmt::color::brown) | fmt::emphasis::bold,
            "w == {thecomplex:$_{width}.{precis}}", "thecomplex"_a=w, "width"_a=20, "precis"_a=20) << std::endl;
    std::cout << fmt::format("w == {thecomplex:,_{width}.{precis}}", "thecomplex"_a=w, "width"_a=20, "precis"_a=20) << std::endl;
    std::cout << fmt::format("w == {thecomplex:|_{width}.{precis}}", "thecomplex"_a=w, "width"_a=20, "precis"_a=20) << std::endl;
    fmt::print(fg(fmt::color::green) | bg(fmt::color::blue) | fmt::emphasis::bold,
            "z == {thecomplex:|_{width}.{precis}}\n", "thecomplex"_a=z, "width"_a=20, "precis"_a=20);
    std::cout << "w == {:|_{}.{}}"_format(w, 20, 20) << std::endl;

    return 0;
}

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Results of compiling and running

Either of the two compiler calls will work I did both to show, I have no idea about other compilers.

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