\LeadsheetsExplLibrary{shorthands}
  {2014/08/10 definition and activation of shorthands}

\seq_new:N   \l__leadsheets_shorthands_seq

\group_begin:
\char_set_catcode_active:N \~

\cs_new_protected:Npn \leadsheets_define_shorthand:Npn #1
  {
    \seq_if_in:NnF \l__leadsheets_shorthands_seq {#1}
      { \seq_put_right:Nn \l__leadsheets_shorthands_seq {#1} }
    \group_begin:
    \__leadsheets_define_shorthand_aux_i:np {#1}
  }

\cs_new_protected:Npn \__leadsheets_define_shorthand_aux_i:np #1#2#{
    \char_set_lccode:nn {`~} {`#1}
    \__leadsheets_define_shorthand_aux_ii:nn {#2}
  }

\cs_new_protected:Npn \__leadsheets_define_shorthand_aux_ii:nn #1#2
  { \tl_to_lowercase:n { \group_end: \cs_set:Npn ~ } #1 {#2} }
\group_end:

\cs_new_protected:Npn \leadsheets_activate_shorthands:n #1
  {
    \tl_map_inline:nn {#1}
      {
        \seq_if_in:NnT \l__leadsheets_shorthands_seq {##1}
          { \char_set_catcode_active:N ##1 }
      }
  }
\cs_new_protected:Npn \leadsheets_activate_all_shorthands:
  {
    \seq_map_inline:Nn \l__leadsheets_shorthands_seq
     { \char_set_catcode_active:N ##1 }
  }

\endinput