seperate auto left-right parens from salign

lecture.cls

@@ -217,15 +217,35 @@
   }
   % replace all relations with align characters (&) and add the needed padding
   \regex_replace_all:nnN
-      { (\c{iff}&|&\c{iff}|\c{impliedby}&|&\c{impliedby}|\c{implies}&|&\c{implies}|\c{approx}&|&\c{approx}|\c{equiv}&|&\c{equiv}|=&|&=|\c{le}&|&\c{le}|\c{ge}&|&\c{ge}|&\c{stackrel}{.*?}{.*?}|\c{stackrel}{.*?}{.*?}&|&\c{neq}|\c{neq}&) }
+  { (\c{iff}&|&\c{iff}|\c{impliedby}&|&\c{impliedby}|\c{implies}&|&\c{implies}|\c{approx}&|&\c{approx}|\c{equiv}&|&\c{equiv}|=&|&=|\c{le}&|&\c{le}|\c{ge}&|&\c{ge}|&\c{stackrel}{.*?}{.*?}|\c{stackrel}{.*?}{.*?}&|&\c{neq}|\c{neq}&|>&|&>|<&|&<) }
       { \c{kern} \u{l_tmp_dim_needed} \1 \c{kern} \u{l_tmp_dim_needed} }
       \l__lec_text_tl
   % replace all parantheses with \left( \right)
+  %\regex_replace_all:nnN { \( } { \c{left}( } \l__lec_text_tl
+  %\regex_replace_all:nnN { \) } { \c{right}) } \l__lec_text_tl
+  %\regex_replace_all:nnN { \[ } { \c{left}[ } \l__lec_text_tl
+  %\regex_replace_all:nnN { \] } { \c{right}] } \l__lec_text_tl
+  \l__lec_text_tl
+ }
+\cs_generate_variant:Nn \lec_insert_padding:n { V }
+
+\NewEnviron{leftright}
+{
+    \lec_replace_parens:V \BODY
+}
+
+% function to replace parens with left right
+\cs_new_protected:Nn \lec_replace_parens:n
+ {
+  \tl_set:Nn \l__lec_text_tl { #1 }
+  % replace all parantheses with \left( \right)
   \regex_replace_all:nnN { \( } { \c{left}( } \l__lec_text_tl
   \regex_replace_all:nnN { \) } { \c{right}) } \l__lec_text_tl
   \regex_replace_all:nnN { \[ } { \c{left}[ } \l__lec_text_tl
   \regex_replace_all:nnN { \] } { \c{right}] } \l__lec_text_tl
   \l__lec_text_tl
  }
-\cs_generate_variant:Nn \lec_insert_padding:n { V }
+\cs_generate_variant:Nn \lec_replace_parens:n { V }
+
 \ExplSyntaxOff
+