Mdthbs

In the code below, what should the definition of sumcounters be to make it sum the current values of the counters thm and lemma?

documentclass{book}

usepackage{amsthm}

usepackage{xparse}

newtheorem{thm}{Theorem}[chapter]

newtheorem{lemma}{Lemma}[chapter]

ExplSyntaxOn

seq_new:N g_my_counters

seq_gput_right:Nn g_my_counters { thm }

seq_gput_right:Nn g_my_counters { lemma }

% NewDocumentCommand{sumcounters}{}{< ? >}

ExplSyntaxOff

begin{document}

chapter{Some chapter}

sumcounters % should print 0



begin{thm}

A theorem.

end{thm}

sumcounters % should print 1



begin{lemma}

A lemma.

end{lemma}

sumcounters % should print 2

end{document}

You could probably do this with a temporary counter, such as l_tmpa_int, but the code below defines a new counter l_counter_sum_int and then the sumcounters macro uses seq_map_inline:Nn to add the current values of the counters in g_my_counters, after which it prints the result. The output is the expected:

Here is the full code:

documentclass{book}

usepackage{amsthm}

usepackage{xparse}

newtheorem{thm}{Theorem}[chapter]

newtheorem{lemma}{Lemma}[chapter]

ExplSyntaxOn

seq_new:N g_my_counters

seq_gput_right:Nn g_my_counters { thm }

seq_gput_right:Nn g_my_counters { lemma }

int_new:N l_counter_sum_int% local counter for adding counter values

NewDocumentCommandsumcounters{}{

  int_zero:N l_counter_sum_int% set l_counter_sum_int to 0

  seq_map_inline:Nn g_my_counters {% add counters in g_my_counters

     int_add:Nn l_counter_sum_int {value{##1}}

  }

  int_use:N l_counter_sum_int% print the result

}

ExplSyntaxOff

begin{document}

chapter{Some chapter}

sumcounters % should print 0



begin{thm}

A theorem.

end{thm}

sumcounters % should print 1



begin{lemma}

A lemma.

end{lemma}

sumcounters % should print 2

end{document}

Instead of performing an assignment, you can also calculate the sum fully-expandably. This has the advantage that you can use it in conditionals, such as

ifnumsumcounters=0 ... fi

I also want to remind you of the expl3 convention to use Hungarian notation for variables, i.e. a variable should carry in its name the data type it holds, usually as a suffix.

documentclass{book}

usepackage{amsthm}

usepackage{xparse}

newtheorem{thm}{Theorem}[chapter]

newtheorem{lemma}{Lemma}[chapter]



ExplSyntaxOn



seq_new:N g_my_counters_seq

seq_gput_right:Nn g_my_counters_seq { thm }

seq_gput_right:Nn g_my_counters_seq { lemma }



cs_new:Npn my_plus_value:n #1

  {

      + (value{#1})

  }



NewExpandableDocumentCommand sumcounters { }

  {

    int_eval:n

      {

        ( 0 seq_map_function:NN g_my_counters_seq my_plus_value:n )

      }

  }



ExplSyntaxOff



begin{document}

chapter{Some chapter}

sumcounters % should print 0



begin{thm}

A theorem.

end{thm}

sumcounters % should print 1



begin{lemma}

A lemma.

end{lemma}

sumcounters % should print 2

end{document}