xsim (17mar20)

git-svn-id: svn://tug.org/texlive/trunk@54380 c570f23f-e606-0410-a88d-b1316a301751

19 files changed, 338 insertions, 131 deletions

diff --git a/Master/texmf-dist/doc/latex/xsim/README b/Master/texmf-dist/doc/latex/xsim/README
index d8f72533c50..e99d361202c 100644
--- a/Master/texmf-dist/doc/latex/xsim/README
+++ b/Master/texmf-dist/doc/latex/xsim/README
@@ -1,5 +1,5 @@
 --------------------------------------------------------------------------
-XSIM     2020/02/23 v0.18
+XSIM     2020/03/16 v0.19
 XSIMVERB 2019/12/29 v0.1a
 
   eXercise Sheets IMproved
diff --git a/Master/texmf-dist/doc/latex/xsim/examples/xsim.collections.tex b/Master/texmf-dist/doc/latex/xsim/examples/xsim.collections.tex
index beca1910055..990391e0915 100644
--- a/Master/texmf-dist/doc/latex/xsim/examples/xsim.collections.tex
+++ b/Master/texmf-dist/doc/latex/xsim/examples/xsim.collections.tex
@@ -5,7 +5,7 @@
 \DeclareExerciseCollection{foo-medium}
 \DeclareExerciseTagging{difficulty}
 
-\usepackage{filecontents,lipsum}
+\usepackage{lipsum}
 \begin{filecontents*}{foo.tex}
 \begin{exercise}[difficulty=easy,points=1]
   foo one \lipsum[4]
diff --git a/Master/texmf-dist/doc/latex/xsim/xsim.history b/Master/texmf-dist/doc/latex/xsim/xsim.history
index 20415de1bff..b957f1e1da9 100644
--- a/Master/texmf-dist/doc/latex/xsim/xsim.history
+++ b/Master/texmf-dist/doc/latex/xsim/xsim.history
@@ -148,3 +148,8 @@ HISTORY:
                    - change \printexercise and \printsolution to accept a
                      clist of either ids or IDs (or mixed)
                    - new templates in the `layouts' style
+ v0.19  2020/03/16 - improve performance
+                   - only set \ExerciseID and \ExerciseType locally to ensure
+                     correct values when exercises (of different types) are
+                     nested
+                   - new load-time option `debug' - only for development
diff --git a/Master/texmf-dist/doc/latex/xsim/xsim_manual.pdf b/Master/texmf-dist/doc/latex/xsim/xsim_manual.pdf
index 03d1892dacb..f3d4e642339 100644
--- a/Master/texmf-dist/doc/latex/xsim/xsim_manual.pdf
+++ b/Master/texmf-dist/doc/latex/xsim/xsim_manual.pdf
diff --git a/Master/texmf-dist/doc/latex/xsim/xsim_manual.tex b/Master/texmf-dist/doc/latex/xsim/xsim_manual.tex
index e301758b606..d3adf284d9b 100644
--- a/Master/texmf-dist/doc/latex/xsim/xsim_manual.tex
+++ b/Master/texmf-dist/doc/latex/xsim/xsim_manual.tex
@@ -68,6 +68,9 @@ using an up to date \TeX\ distribution, anyway.
   package.  Be careful: if you're in the middle of an important project it
   might be better to wait with the update until you've finished the project.
   Every update might be breaking some things.
+
+  Please also be aware that \xsim\ is actively developed and many things may
+  still change.  However, I will try my best to keep the interface stable.
 \end{bewareofthedog}
 
 \section{Motivation and Background}
@@ -1483,6 +1486,10 @@ yourself in order to achieve certain layouts\footnote{I plan to incorporate
     Can be used to refer to the current exercise type.
   \expandable\command{ExerciseID}
     Can be used to refer to the current exercise id.
+  \expandable\command{ExerciseText}
+    Can be used inside solutions to retrieve the text of the corresponding
+    solution.  This is propably seldom useful as in most use cases the
+    exercise property \property{solution} is the easier alternative.
   \expandable\command{ExerciseCollection}
     Can be used in certain templates to refer to the collection that is
     currently inserted.
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim-manual.cls b/Master/texmf-dist/tex/latex/xsim/xsim-manual.cls
index 1171fe9dd24..e40029df10b 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim-manual.cls
+++ b/Master/texmf-dist/tex/latex/xsim/xsim-manual.cls
@@ -492,7 +492,7 @@
 \tcbset{enhanced,enhanced jigsaw}
 
 \newtcolorbox{bewareofthedog}{
-  colback  = white ,
+  colback  = red!2!white!98 ,
   colframe = red ,
   underlay={%
     \path[draw=none]
@@ -597,6 +597,76 @@
     \endcnltxcode
   }
 
+\RenewDocumentEnvironment{sourcecode}{}
+  {%
+    \xsimman@readoptions{%
+      \setlength\cnltx@sidebysidewidth
+        {\dimexpr .45\columnwidth -\lst@xleftmargin -\lst@xrightmargin\relax}%
+      \XSIMexpandcode{%
+        \noexpand\lstset{
+          style=cnltx,
+          \ifboolexpe{ bool {cnltx@sidebyside} and not bool {cnltx@codeonly} }
+            {linewidth=\cnltx@sidebysidewidth,}{}%
+          \expandonce\cnltx@local@listings@options
+        }%
+      }%
+      \XSIMgobblechars{2}%
+    }%
+  }
+  {%
+    \XSIMfilewritestop
+    \cnltxcode[breakable]%
+    \lstinputlisting[style=cnltx]{\jobname.tmp}%
+    \endcnltxcode
+  }
+
+\RenewDocumentEnvironment{example}{}
+  {%
+    \xsimman@readoptions{%
+      \setlength\cnltx@sidebysidewidth
+        {\dimexpr .45\columnwidth -\lst@xleftmargin -\lst@xrightmargin\relax}%
+      \XSIMexpandcode{%
+        \noexpand\lstset{
+          style=cnltx,
+          \ifboolexpe{ bool {cnltx@sidebyside} and not bool {cnltx@codeonly} }
+            {linewidth=\cnltx@sidebysidewidth,}{}%
+          \expandonce\cnltx@local@listings@options
+        }%
+      }%
+      \XSIMgobblechars{2}%
+    }%
+  }
+  {%
+    \XSIMfilewritestop
+    \catcode`\^^M=5
+    \ifbool{cnltx@sidebyside}
+      {%
+        \cnltxcode
+        \noindent
+        \minipage[c]{\cnltx@sidebysidewidth}%
+          \cnltx@pre@source@hook
+          \lstinputlisting[style=cnltx] {\jobname.tmp}%
+          \cnltx@after@source@hook
+        \endminipage\hfill
+        \minipage[c]{\cnltx@sidebysidewidth}%
+          \cnltx@pre@example@hook
+          \input {\jobname.tmp}%
+          \cnltx@after@example@hook
+        \endminipage
+      }
+      {%
+        \cnltxcode[breakable]%
+        \cnltx@pre@source@hook
+        \lstinputlisting{\jobname.tmp}%
+        \cnltx@after@source@hook
+        \tcblower
+        \cnltx@pre@example@hook
+        \input {\jobname.tmp}%
+        \cnltx@after@example@hook
+      }%
+    \endcnltxcode
+  }
+
 \renewrobustcmd*\inputsourcecode[2][]{%
   \begingroup
     \pgfqkeys{/cnltx}{#1}%
@@ -899,6 +969,7 @@
 \xsim@add@version{0.16a} {2020-01-16}
 \xsim@add@version{0.17}  {2020-02-21}
 \xsim@add@version{0.18}  {2020-02-23}
+\xsim@add@version{0.19}  {2020-03-16}
 
 % ----------------------------------------------------------------------------
 \newrobustcmd*\xsimauxfileinfo{%
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.auxfile.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.auxfile.code.tex
index 4fa95620a35..2f31f2009f5 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.auxfile.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.auxfile.code.tex
@@ -105,19 +105,17 @@
 \cs_new_protected:Npn \xsim_new_list:n #1
   {
     \xsim_verbose:n { Defining~ new~ auxfile~ list~ `#1'. }
-    \prop_new:c {g__xsim_list_#1_prop}
     \seq_new:c {g__xsim_list_#1_seq}
     \seq_new:c {g__xsim_list_recorded_#1_seq}
     \xsim_new_aux_property:cpn {#1} ##1
       {
-        \prop_gclear:c {g__xsim_list_#1_prop}
         \tl_if_blank:nF {##1}
           {
             \seq_gset_split:cVx {g__xsim_list_#1_seq}
               \l__xsim_split_aux_lists_str
               { \tl_to_str:n {##1} }
             \seq_map_inline:cn {g__xsim_list_#1_seq}
-              { \prop_gput:cnn {g__xsim_list_#1_prop} {####1} {} }
+              { \xsim_attribute_set:nnn {#1} {####1} {} }
           }
       }
     \xsim_at_begin_document:n
@@ -140,7 +138,7 @@
   {
     \xsim_verbose:n { Adding~ `#2'~ to~ list~ `#1'. }
     \str_set:Nn \l__xsim_tmpa_str {#2}
-    \prop_gput:cnn {g__xsim_list_#1_prop} {#2} {}
+    \xsim_attribute_set:nnn {#1} {#2} {}
     \seq_if_in:cVT {g__xsim_list_#1_seq} \l__xsim_tmpa_str
       { \seq_gremove_all:cV {g__xsim_list_#1_seq} \l__xsim_tmpa_str }
     \seq_gput_right:cV {g__xsim_list_#1_seq} \l__xsim_tmpa_str
@@ -153,8 +151,8 @@
   {
     \xsim_verbose:n { Removing~ `#2'~ to~ list~ `#1'. }
     \str_set:Nn \l__xsim_tmpa_str {#2}
-    \prop_if_in:cnT {g__xsim_list_#1_prop} {#2}
-      { \prop_gremove:cn {g__xsim_list_#1_prop} {#2} }
+    \xsim_attribute_if_set:nnT {#1} {#2}
+      { \xsim_attribute_unset:nn {#1} {#2} }
     \seq_if_in:cVT {g__xsim_list_#1_seq} \l__xsim_tmpa_str
       { \seq_gremove_all:cV {g__xsim_list_#1_seq} \l__xsim_tmpa_str }
     \seq_if_in:cVT {g__xsim_list_recorded#1_seq} \l__xsim_tmpa_str
@@ -167,16 +165,13 @@
 % #2: entry
 \prg_new_conditional:Npnn \xsim_if_in_list:nn #1#2 {p,T,F,TF}
   {
-    \prop_if_in:cnTF {g__xsim_list_#1_prop} {#2}
+    \xsim_attribute_if_set:nnTF {#1} {#2}
       { \prg_return_true: }
       { \prg_return_false: }
   }
 \cs_generate_variant:Nn \xsim_if_in_list:nnTF {nx}
 \cs_generate_variant:Nn \xsim_if_in_list:nnT  {nx}
 
-\cs_new:Npn \xsim_list_show:n #1
-  { \prop_show:c {g__xsim_list_#1_prop}  }
-
 \bool_new:N \l__xsim_empty_lists_bool
 \cs_new_protected:Npn \xsim_empty_lists:
   { \bool_set_true:N \l__xsim_empty_lists_bool }
@@ -223,3 +218,4 @@
 
 % ----------------------------------------------------------------------------
 \file_input_stop:
+2020/03/16 - performance optimizations
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.base.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.base.code.tex
index fbaf246c0f5..3bcfb21d36a 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.base.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.base.code.tex
@@ -53,7 +53,7 @@
 \cs_generate_variant:Nn \seq_if_in:NnT      {cV}
 \cs_generate_variant:Nn \seq_gremove_all:Nn {cV}
 \cs_generate_variant:Nn \seq_gput_right:Nn  {cV}
-\cs_generate_variant:Nn \prop_put:Nnn       {cxx}
+\cs_generate_variant:Nn \prop_put:Nnn       {Nnx,cxx}
 \cs_generate_variant:Nn \prop_gput:Nnn      {Nx,Nnx,cxx}
 \cs_generate_variant:Nn \prop_item:Nn       {c}
 \cs_generate_variant:Nn \prop_if_in:NnTF    {Nx}
@@ -68,12 +68,11 @@
 \cs_generate_variant:Nn \tl_if_eq:nnTF      {ff,V}
 \cs_generate_variant:Nn \tl_if_eq:nnT       {x}
 \cs_generate_variant:Nn \tl_if_blank:nTF    {f}
-\cs_generate_variant:Nn \tl_set_rescan:Nnn  {Nnn}
+\cs_generate_variant:Nn \tl_set_rescan:Nnn  {Nnx}
 \cs_generate_variant:Nn \iow_now:Nn         {NV}
 \cs_generate_variant:Nn \str_if_eq:nnT      {x}
 \cs_generate_variant:Nn \str_if_eq:nnF      {xx}
 \cs_generate_variant:Nn \str_if_eq_p:nn     {e}
-\cs_generate_variant:Nn \iow_now:Nn         {NV}
 \cs_generate_variant:Nn \prg_new_protected_conditional:Npnn {c}
 
 % ----------------------------------------------------------------------------
@@ -136,6 +135,13 @@
       { \prg_return_false: }
   }
 
+\prg_new_conditional:Npnn \xsim_if_debug: {p,T,F,TF}
+  {
+    \bool_if:NTF \g__xsim_debug_bool
+      { \prg_return_true: }
+      { \prg_return_false: }
+  }
+
 \prg_new_conditional:Npnn \xsim_if_package_blank: {p,T,F,TF}
   {
     \bool_if:NTF \g__xsim_blank_bool
@@ -198,8 +204,78 @@
 
 % ----------------------------------------------------------------------------
 
+\msg_new:nnn {xsim} {attribute-not-set}
+  { The~ attribute~ `#1'~ is~ not~ set~ \msg_line_context: }
+
+% #1: attribute
+% #2: item
+\cs_new_protected:Npn \xsim_attribute_new:nn #1#2
+  { \cs_new:cpn {____xsim_attribute_ \tl_to_str:n {#1::#2} :} {} }
+  
+% #1: attribute
+% #2: item
+% #3: value
+\cs_new_protected:Npn \xsim_attribute_set:nnn #1#2#3
+  { \cs_gset:cpx {____xsim_attribute_ \tl_to_str:n {#1::#2} :} { \exp_not:n {#3} } }
+\cs_generate_variant:Nn \xsim_attribute_set:nnn {nnx}
+
+% #1: attribute
+% #2: item
+\cs_new_protected:Npn \xsim_attribute_unset:nn #1#2
+  { \cs_undefine:c {____xsim_attribute_ \tl_to_str:n {#1::#2} :} }
+  
+% #1: attribute
+% #2: item
+\cs_new:Npn \xsim_attribute_get:nn #1#2
+  {
+    \cs_if_exist:cTF {____xsim_attribute_ \tl_to_str:n {#1::#2} :}
+      { \use:c {____xsim_attribute_ \tl_to_str:n {#1::#2} :} }
+      {
+        \xsim_if_debug:T
+          { \msg_expandable_error:nnn {xsim} {attribute-not-set} {#1::#2} }
+      }
+  }
+
+% #1: attribute
+% #2: item
+\prg_new_conditional:Npnn \xsim_attribute_if_set:nn #1#2 {p,T,F,TF}
+  {
+    \cs_if_exist:cTF {____xsim_attribute_ \tl_to_str:n {#1::#2} :}
+      { \prg_return_true: }
+      { \prg_return_false: }
+  }
+
+% #1: attribute
+% #2: item
+\prg_new_conditional:Npnn \__xsim_if_attribute_eq:nnn #1#2#3 {p,T,F,TF}
+  {
+    \tl_if_eq:enTF
+      { \use:c {____xsim_attribute_ \tl_to_str:n {#1::#2} :} }
+      {#3}
+      { \prg_return_true: }
+      { \prg_return_false: }
+  }
+
+% #1: attribute
+% #2: item
+\cs_new_protected:Npn \xsim_attribute_show:nn #1#2
+  {
+    \iow_term:n {}
+    \iow_term:x
+      {
+        \c_space_tl \c_space_tl
+        \tl_to_str:n {#1::#2}
+        \c_space_tl \c_space_tl == \c_space_tl \c_space_tl
+        {\use:c {____xsim_attribute_ \tl_to_str:n {#1::#2} :}}
+      }
+    \iow_term:n {}
+  }
+
+% ----------------------------------------------------------------------------
+
 \cs_new_protected:Npn \xsim_setup:n #1
   { \keys_set:nn {xsim} {#1} }
 
 % ----------------------------------------------------------------------------
 \file_input_stop:
+2020/03/15 - alternative to property lists for performance optimizations
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.collections.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.collections.code.tex
index b85ffa2a156..5aeb6e2d77e 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.collections.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.collections.code.tex
@@ -29,7 +29,7 @@
 
 \xsim_load_modules:n {base}
 
-\prop_new:N \g__xsim_collections_prop
+\seq_new:N \g__xsim_collections_seq
 \bool_new:N \l____xsim_active_bool
 
 \msg_new:nnn {xsim} {collection-exists}
@@ -66,7 +66,8 @@
       { \msg_error:nnn {xsim} {collection-exists} {#1} }
       {
         \xsim_verbose:n { Declaring~ new~ collection~ `#1'. }
-        \prop_gput:Nnn \g__xsim_collections_prop {#1} { \c_false_bool }
+        \xsim_attribute_set:nnn {collection} {#1} { \c_false_bool }
+        \seq_gput_right:Nn \g__xsim_collections_seq {#1}
         \xsim_new_list:n {collection:#1}
         \seq_new:c {g__xsim_collection_#1_seq}
       }
@@ -75,7 +76,7 @@
 % #1: collection name
 \prg_new_conditional:Npnn \xsim_if_collection_exist:n #1 {T,F,TF}
   {
-    \prop_if_in:NnTF \g__xsim_collections_prop {#1}
+    \seq_if_in:NnTF \g__xsim_collections_seq {#1}
       { \prg_return_true: }
       { \prg_return_false: }
   }
@@ -83,7 +84,9 @@
 \xsim_new_collection:n {all~ exercises}
 
 \cs_new_protected:Npn \xsim_foreach_collection:n #1
-  { \prop_map_inline:Nn \g__xsim_collections_prop {#1} }
+  { \seq_map_inline:Nn \g__xsim_collections_seq {#1} }
+
+\cs_new:Npn \xsim_collection_map_break: { \seq_map_break: }
 
 % ----------------------------------------------------------------------------
 
@@ -96,7 +99,7 @@
       }
       {
         \xsim_verbose:n { Activating~ collection~ `#1'. }
-        \prop_gput:Nnn \g__xsim_collections_prop {#1} { \c_true_bool }
+        \xsim_attribute_set:nnn {collection} {#1} { \c_true_bool }
         \tl_if_blank:nF {#2}
           { \seq_gput_right:cn {g__xsim_collection_#1_seq} {#2} }
       }
@@ -111,8 +114,8 @@
     \xsim_if_collection_active:nTF {#1}
       {
         \xsim_verbose:n { Deactivating~ collection~ `#1'. }
-        \prop_gput:Nnn \g__xsim_collections_prop {#1} { \c_false_bool }
-        \seq_gclear:c {g__xsim_collection_#1_seq}
+        \xsim_attribute_set:nnn {collection} {#1} { \c_false_bool }
+        % \seq_gclear:c {g__xsim_collection_#1_seq}
       }
       { % TODO: warning
       }
@@ -161,7 +164,7 @@
     \seq_if_empty:cTF {g__xsim_collection_#1_seq}
       { \__xsim_add_to_collection:nnn {#1} {#2} {#3} }
       {
-        \seq_if_in:cnT {g__xsim_collection_#1_seq} {#2}
+        \seq_if_in:cnF {g__xsim_collection_#1_seq} {#2}
           { \__xsim_add_to_collection:nnn {#1} {#2} {#3} }
       }
   }
@@ -349,11 +352,11 @@
 % #1: collection name
 \prg_new_conditional:Npnn \xsim_if_collection_active:n #1 {T,F,TF}
   {
-    \prop_if_in:NnTF \g__xsim_collections_prop {#1}
+    \xsim_attribute_if_set:nnTF {collection} {#1}
       {
         \bool_lazy_and:nnTF
           { !\str_if_eq_p:en {#1} {all~ exercises} }
-          { \prop_item:Nn \g__xsim_collections_prop {#1} }
+          { \xsim_attribute_get:nn {collection} {#1} }
           { \prg_return_true: }
           { \prg_return_false: }
       }
@@ -363,12 +366,12 @@
 \prg_new_protected_conditional:Npnn \xsim_if_collections_active: {T,F,TF}
   {
     \bool_set_false:N \l____xsim_active_bool
-    \prop_map_inline:Nn \g__xsim_collections_prop
+    \xsim_foreach_collection:n
       {
         \xsim_if_collection_active:nT {##1}
           {
             \bool_set_true:N \l____xsim_active_bool
-            \prop_map_break:
+            \xsim_collection_map_break:
           }
       }
     \bool_if:NTF \l____xsim_active_bool
@@ -381,7 +384,7 @@
 \xsim_at_begin_document:n
   {
     \xsim_get_collections:
-    \xsim_activate_collection:n   {all~ exercises}
+    \xsim_activate_collection:n {all~ exercises}
   }
 
 \xsim_at_end_document:n
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.environments.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.environments.code.tex
index ce4b281ba02..ca5f76f80a7 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.environments.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.environments.code.tex
@@ -55,9 +55,6 @@
 \tl_new:N  \ExerciseText
 \tl_set:Nn \ExerciseText { \msg_error:nn {xsim} {only-in-solution} }
 
-\cs_generate_variant:Nn \tl_set_rescan:Nnn {Nnx}
-\cs_generate_variant:Nn \prop_put:Nnn {Nnx}
-
 % ----------------------------------------------------------------------------
 
 \msg_new:nnn {xsim} {only-in-solution}
@@ -277,6 +274,8 @@
 % #3: exercise|solution
 \cs_new_protected:Npn \xsim_typeset_environment:nnn #1#2#3
   {
+    \tl_set:Nn \ExerciseType {#1}
+    \tl_set:Nn \ExerciseID {#2}
     \xsim_if_exchange:nnnT {#1} {#2} {#3}
       { \__xsim_set_file_signature:nnn {#1} {#2} {exercise} }
     \xsim_verbose:n
@@ -507,7 +506,7 @@
                 \bool_set_true:N \l__xsim_options_given_bool
                 \use:c {xsim_start_#2:nn} {#1} {##1}
               }
-              \xsim_start_environment:nVnn {#1} \g_xsim_exercise_id_tl {#2} {##2}
+            \xsim_start_environment:nVnn {#1} \g_xsim_exercise_id_tl {#2} {##2}
           }
           {
             \xsim_stop_environment:nVn {#1} \g_xsim_exercise_id_tl {#2}
@@ -526,3 +525,5 @@
 2020/02/19 - implement issue #33 (solution property)
 2020/02/20 - fix issue #27
            - implement issue #2
+2020/03/08 - correctly re-set \ExerciseType and \ExerciseID for typesetting
+             (they're no longer local)
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.exercises.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.exercises.code.tex
index 2fc9e4d142b..9ba49c68033 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.exercises.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.exercises.code.tex
@@ -33,15 +33,16 @@
     collections
   }
 
+\seq_new:N  \l__xsim_exercise_types_seq
 \seq_new:N  \l__xsim_parameters_seq
 \seq_new:N  \l__xsim_fixed_parameters_seq
 \seq_new:N  \l__xsim_mandatory_parameters_seq
-\prop_new:N \g__xsim_exercises_prop
 \int_gzero_new:N  \g_xsim_id_int
 \int_gzero_new:N  \g_xsim_max_id_int
 \tl_new:N   \l_xsim_current_id_tl
 \tl_new:N   \g_xsim_exercise_id_tl
 \tl_new:N   \ExerciseID
+\tl_new:N   \ExerciseType
 \bool_new:N \l____xsim_print_bool
 
 % ----------------------------------------------------------------------------
@@ -73,6 +74,28 @@
   }
 
 % ----------------------------------------------------------------------------
+% #1: type
+% #2: parameter
+% #3: value
+\cs_new_protected:Npn \__xsim_set_parameter_type:nnn #1#2#3
+  { \xsim_attribute_set:nnn {#1} {#2} {#3} }
+
+% #1: type
+% #2: parameter
+\cs_new:Npn \xsim_get_parameter:nn #1#2
+  { \xsim_attribute_get:nn {#1} {#2} }
+\cs_generate_variant:Nn \xsim_get_parameter:nn {o}
+
+% #1: type
+% #2: parameter
+\prg_new_conditional:Npnn \xsim_if_parameter_set:nn #1#2 {p,T,F,TF}
+  {
+    \xsim_attribute_if_set:nnTF {#1} {#2}
+      { \prg_return_true: }
+      { \prg_return_false: }
+  }
+
+% ----------------------------------------------------------------------------
 
 \xsim_new_list:n {types}
 
@@ -141,7 +164,7 @@
 % #1: type
 \prg_new_conditional:Npnn \xsim_if_type:n #1 {p,T,F,TF}
   {
-    \prop_if_exist:cTF {l__xsim_#1_type_parameters_prop}
+    \seq_if_in:NnTF \l__xsim_exercise_types_seq {#1}
       { \prg_return_true: }
       { \prg_return_false: }
   }
@@ -167,31 +190,18 @@
               {
                 \xsim_verbose:n
                   { Setting~ parameter~ `#2'~ for~ type~ `#1'~ to~ `#3'. }
-                \prop_put:cnn {l__xsim_#1_type_parameters_prop} {#2} {#3}
+                \__xsim_set_parameter_type:nnn {#1} {#2} {#3}
               }
           }
           {
             \xsim_verbose:n
               { Setting~ parameter~ `#2'~ for~ type~ `#1'~ to~ `#3'. }
-            \prop_put:cnn {l__xsim_#1_type_parameters_prop} {#2} {#3}
+            \__xsim_set_parameter_type:nnn {#1} {#2} {#3}
           }
       }
   }
 \cs_generate_variant:Nn \xsim_set_parameter:nnn {nnx,nxx}
 
-% #1: type
-% #2: parameter
-\cs_new:Npn \xsim_get_parameter:nn #1#2
-  { \prop_item:cn {l__xsim_#1_type_parameters_prop} {#2} }
-\cs_generate_variant:Nn \xsim_get_parameter:nn {o}
-
-\prg_new_conditional:Npnn \xsim_if_parameter_set:nn #1#2 {p,T,F,TF}
-  {
-    \prop_if_in:cnTF {l__xsim_#1_type_parameters_prop} {#2}
-      { \prg_return_true: }
-      { \prg_return_false: }
-  }
-
 \cs_new:Npn \__xsim_get_parameter_tmp:n #1 {}
 \cs_generate_variant:Nn \__xsim_get_parameter_tmp:n {V}
 
@@ -274,7 +284,7 @@
 
 \cs_new_protected:Npn \xsim_define_exercise_type_variables:n #1
   {
-    \prop_new:c {l__xsim_#1_type_parameters_prop}
+    \seq_put_right:Nn \l__xsim_exercise_types_seq {#1}
     \bool_new:c {l__xsim_#1_solution_print_bool}
     \bool_new:c {l__xsim_#1_exercise_print_bool}
     \bool_new:c {l__xsim_#1_exercise_use_bool}
@@ -320,22 +330,22 @@
         \xsim_if_parameter_set:nnF {#1} {exercises-name}
           {
             \xsim_set_parameters:nn {#1}
-              { exercises-name =  \xsim_get_parameter:nn {#1} {exercise-name} s }
+              { exercises-name = \xsim_get_parameter:nn {#1} {exercise-name} s }
           }
         \xsim_if_parameter_set:nnF {#1} {solutions-name}
           {
             \xsim_set_parameters:nn {#1}
-              { solutions-name =  \xsim_get_parameter:nn {#1} {solution-name} s }
+              { solutions-name = \xsim_get_parameter:nn {#1} {solution-name} s }
           }
         \xsim_if_parameter_set:nnF {#1} {counter}
           {
             \xsim_set_parameters:nx {#1}
-              { counter =  \xsim_get_parameter:nn {#1} {exercise-env} }
+              { counter = \xsim_get_parameter:nn {#1} {exercise-env} }
           }
         \xsim_if_parameter_set:nnF {#1} {solution-counter}
           {
             \xsim_set_parameters:nx {#1}
-              { solution-counter =  \xsim_get_parameter:nn {#1} {solution-env} }
+              { solution-counter = \xsim_get_parameter:nn {#1} {solution-env} }
           }
         \xsim_define_counters:n {#1}
         \xsim_verbose:n { Defining~ options~ for~ new~ exercise~ type~ `#1' }
@@ -363,8 +373,12 @@
               .code:n = \xsim_set_parameter:nnn {#1} {solution-template} {####1} ,
             \xsim_get_parameter:nn {#1} {exercise-env} / name
               .code:n = \xsim_set_parameter:nnn {#1} {exercise-name} {####1} ,
+            \xsim_get_parameter:nn {#1} {exercise-env} s / name
+              .code:n = \xsim_set_parameter:nnn {#1} {exercises-name} {####1} ,
             \xsim_get_parameter:nn {#1} {solution-env} / name
               .code:n = \xsim_set_parameter:nnn {#1} {solution-name} {####1} ,
+            \xsim_get_parameter:nn {#1} {solution-env} s / name
+              .code:n = \xsim_set_parameter:nnn {#1} {solutions-name} {####1} ,
             \xsim_get_parameter:nn {#1} {exercise-env} / heading
               .code:n = \xsim_set_parameter:nnn {#1} {exercise-heading} {####1} ,
             \xsim_get_parameter:nn {#1} {solution-env} / heading
@@ -395,6 +409,7 @@
         \int_compare:nF { \g_xsim_max_id_int > \g_xsim_id_int }
           { \int_gset_eq:NN \g_xsim_max_id_int \g_xsim_id_int }
         \tl_gset:Nx \g_xsim_exercise_id_tl { \int_use:N \g_xsim_id_int }
+        \tl_gset:Nn \g_xsim_exercise_type_tl {#1}
         % save the goal values from the auxiliary files:
         \xsim_foreach_goal:n
           {
@@ -467,11 +482,8 @@
                 chapter = \thechapter
               }
           }
-        % \tl_gclear:N \g_xsim_exercise_id_tl
-        % \xsim_gsave_property:nVnN {#1} \l__xsim_tmpa_tl {id}
-        %   \g_xsim_exercise_id_tl
-        \tl_gset_eq:NN \ExerciseID \g_xsim_exercise_id_tl
-        \tl_gset:Nn \ExerciseType {#1}
+        \tl_set_eq:NN \ExerciseID \g_xsim_exercise_id_tl
+        \tl_set:Nn \ExerciseType {#1}
         \xsim_verbose:x
           {
             Starting~ exercise~ type~ `#1' with~ id~
@@ -505,7 +517,11 @@
       }
   }
 
-\cs_new_protected:Npn \xsim_stop_exercise:n #1 {}
+\cs_new_protected:Npn \xsim_stop_exercise:n #1
+  {
+    \xsim_if_insert_mode:F
+      { \tl_gset_eq:NN \g_xsim_exercise_id_tl \ExerciseID }
+  }
 
 % ----------------------------------------------------------------------------
 % #1: type
@@ -615,3 +631,6 @@
 \file_input_stop:
 
 2020/02/21 - implement issue #2
+2020/03/01 - add options `<ex-env>s/name` and `<sol-env>/name`
+2020/03/07 - set \ExerciseID and \ExerciseType only locally
+2020/03/14 - performance optimizations
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.goals.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.goals.code.tex
index 6b17d2bc3f5..67019eb6f36 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.goals.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.goals.code.tex
@@ -156,7 +156,7 @@
 \prg_new_conditional:Npnn \xsim_if_goal_value:nnnn #1#2#3#4 {p,T,F,TF}
   {
     \fp_compare:nTF
-      { (0 \xsim_get_property:nnn {#1} {#2} {#3}) #4 }
+      { (0 + \xsim_get_property:nnn {#1} {#2} {#3}) #4 }
       { \prg_return_true: }
       { \prg_return_false: }
   }
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.interface.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.interface.code.tex
index b0ca92a1c47..b96e5a47b5d 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.interface.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.interface.code.tex
@@ -332,8 +332,8 @@
 \NewExpandableDocumentCommand \XSIMtranslate {m}
   { \xsim_translate:n {#1} }
 
-\NewDocumentCommand \XSIMexpandcode {+m}
-  { \use:x {#1} }
+\NewExpandableDocumentCommand \XSIMexpandcode {+m}
+  { \use:e {#1} }
 
 \NewExpandableDocumentCommand \XSIMmixedcase {m}
   { \tl_mixed_case:f {#1} }
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.modules.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.modules.code.tex
index bc82dcbafc7..51b595fdd37 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.modules.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.modules.code.tex
@@ -87,7 +87,7 @@
           { \msg_error:nnn {xsim} {module-missing} {#1} }
       }
   }
-\cs_generate_variant:Nn \__xsim_load_module:n { V }
+\cs_generate_variant:Nn \__xsim_load_module:n {V}
 
 \prg_new_conditional:Npnn \xsim_if_module_loaded:n #1 {p,T,F,TF}
   {
@@ -163,8 +163,6 @@
     \tl_set:Nx \l__xsim_module_version_tl {\c_xsim_version_tl}
   }
 
-\cs_generate_variant:Nn \str_if_eq:nnF {xx}
-
 \cs_new_protected:Npn \__xsim_module:nn #1#2
   {
     \seq_gput_right:Nn \g__xsim_loaded_modules_seq {#1}
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.properties.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.properties.code.tex
index 0bbc972f219..12a6fdf220b 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.properties.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.properties.code.tex
@@ -49,13 +49,39 @@
     \msg_line_context: . \\
     However,~ property~ `#1'~ is~ not~ a~ boolean~ property!
   }
-  
+
+\msg_new:nnn {xsim} {unbalanced-property-list}
+  {
+    There~ is~ a~ mis-match~ in~ the~ property~ list: \\
+    `#1' \\
+    \msg_line_context:
+  }
+
 \seq_new:N \l__xsim_properties_seq
 \seq_new:N \l__xsim_boolean_properties_seq
 \seq_new:N \l__xsim_unique_properties_seq
 \seq_new:N \l__xsim_noupdate_properties_seq
 \seq_new:N \l__xsim_given_properties_seq
-\prop_new:N \g__xsim_properties_prop
+
+% #1: type
+% #2: id
+% #3: property
+\cs_new_protected:Npn \__xsim_define_property:nnn #1#2#3
+  { \xsim_attribute_new:nn {#1!#2} {#3} }
+
+% check if property is set:
+% #1: type
+% #2: id
+% #3: property
+\prg_new_conditional:Npnn \xsim_if_property_set:nnn #1#2#3 {p,T,F,TF}
+  {
+    \xsim_attribute_if_set:nnTF {#1!#2} {#3}
+      { \prg_return_true: }
+      { \prg_return_false: }
+  }
+\prg_generate_conditional_variant:Nnn \xsim_if_property_set:nnn
+  {nx,nnx,xx,nV}
+  {T,F,TF}
 
 % new property:
 % #1: boolean if unique
@@ -88,8 +114,6 @@
                 \seq_if_in:NnF \l__xsim_unique_properties_seq {#4}
                   { \seq_put_right:Nn \l__xsim_unique_properties_seq {#4} }
                 \seq_new:c {l__xsim_unique_property_#4_values_seq}
-                \prop_new:c {g__xsim_property_#4_type_prop}
-                \prop_new:c {g__xsim_property_#4_id_prop}
               }
               { \xsim_verbose:n { Declaring~ new~ exercise~ property~ `#4'. } }
           }
@@ -160,27 +184,27 @@
 % #4: value
 \cs_new_protected:Npn \xsim_set_property:nnnn #1#2#3#4
   {
-    \xsim_if_property_exist:nTF {#3}
+    \xsim_if_property_exist:nTF {#3} % _p
       {
-        \xsim_if_property_set:nnnTF {#1} {#2} {#3}
+        \xsim_if_property_set:nnnTF {#1} {#2} {#3} % _p
           {
-            \xsim_if_property_unique_value:nnTF {#3} {#4}
+            \xsim_if_property_unique_value:nnTF {#3} {#4} %_p
               { \msg_warning:nnnn {xsim} {property-unique} {#3} {#4} }
               {
-                \xsim_if_property_boolean:nTF {#3}
+                \xsim_if_property_boolean:nTF {#3} % _p
                   { \__xsim_set_boolean_property:nnnn {#1} {#2} {#3} {#4} }
                   {
-                    \xsim_if_property_unique:nTF {#3}
+                    \xsim_if_property_unique:nTF {#3} % _p
                       { \__xsim_set_unique_property:nnnn {#1} {#2} {#3} {#4} }
                       { \__xsim_set_property:nnnn {#1} {#2} {#3} {#4} }
                   }
               }
           }
           {
-            \xsim_if_property_boolean:nTF {#3}
+            \xsim_if_property_boolean:nTF {#3} % _p
               { \__xsim_set_boolean_property:nnnn {#1} {#2} {#3} {#4} }
               {
-                \xsim_if_property_unique:nTF {#3}
+                \xsim_if_property_unique:nTF {#3} % _p
                   { \__xsim_set_unique_property:nnnn {#1} {#2} {#3} {#4} }
                   { \__xsim_set_property:nnnn {#1} {#2} {#3} {#4} }
               }
@@ -218,6 +242,17 @@
 % #1: type
 % #2: id
 % #3: property
+\cs_new_protected:Npn \__xsim_unset_property:nnn #1#2#3
+  {
+    \xsim_verbose:n
+      { Un-setting~ property~ `#3'~ of~ exercise~ type~ `#1'~ id~ `#2'. }
+    \__xsim_remove_property_from_list:nnn {#1} {#2} {#3}
+    \xsim_attribute_unset:nn {#1!#2} {#3}
+  }
+
+% #1: type
+% #2: id
+% #3: property
 \cs_new_protected:Npn \xsim_unset_property:nnn #1#2#3
   {
     \xsim_if_property_exist:nTF {#3}
@@ -237,10 +272,10 @@
         Setting~ property~ `#3'~ of~ exercise~ type~ `#1'~ id~ `#2'~ to~
         value~ `#4'.
       }
-   \__xsim_remove_property_from_list:nnn {#1} {#2} {#3}
+    \__xsim_remove_property_from_list:nnn {#1} {#2} {#3}
     % now we can safely add the property to the list:
     \xsim_add_to_list:nn {#3} {#1-#2=={#4}}
-    \prop_gput:Nnn \g__xsim_properties_prop {#2!#1!#3} {#4}
+    \xsim_attribute_set:nnn {#1!#2} {#3} {#4}
   }
 \cs_generate_variant:Nn \__xsim_set_property:nnnn {VVnV}
 
@@ -250,19 +285,8 @@
 % #4: value
 \cs_new_protected:Npn \__xsim_set_property_reverse:nnnn #1#2#3#4
   {
-    \prop_gput:cnn {g__xsim_property_#3_type_prop} {#4} {#1}
-    \prop_gput:cnn {g__xsim_property_#3_id_prop} {#4} {#2}
-  }
-
-% #1: type
-% #2: id
-% #3: property
-\cs_new_protected:Npn \__xsim_unset_property:nnn #1#2#3
-  {
-    \xsim_verbose:n
-      { Un-setting~ property~ `#3'~ of~ exercise~ type~ `#1'~ id~ `#2'. }
-    \__xsim_remove_property_from_list:nnn {#1} {#2} {#3}
-    \prop_gremove:Nn \g__xsim_properties_prop {#2!#1!#3}
+    \xsim_attribute_set:nnn {type:#3} {#4} {#1}
+    \xsim_attribute_set:nnn {id:#3} {#4} {#2}
   }
 
 \tl_set:Nx \l__xsim_tmpa_tl { \cs_to_str:N \{ }
@@ -280,6 +304,9 @@
     \str_set:Nn #3 {#6}
   }
 
+% #1: type
+% #2: id
+% #3: property
 \cs_new_protected:Npn \__xsim_remove_property_from_list:nnn #1#2#3
   {
     % make sure we change the entry if it has been recorded previously:
@@ -331,6 +358,8 @@
     \clist_map_inline:nn {#3}
       {
         \seq_set_split:Nnx \l__xsim_tmpa_seq {=} { \tl_trim_spaces:n {##1} }
+        \int_compare:nNnT { \seq_count:N \l__xsim_tmpa_seq } > {2}
+          { \msg_error:nnn {xsim} {unbalanced-property-list} {##1} }
         \xsim_set_property:nnxx
           {#1}
           {#2}
@@ -343,36 +372,21 @@
   }
 \cs_generate_variant:Nn \xsim_set_properties:nnn {nnx,nxx,nV,nVx}
 
-% check if property is set:
-% #1: type
-% #2: id
-% #3: property
-\prg_new_conditional:Npnn \xsim_if_property_set:nnn #1#2#3 {T,F,TF}
-  {
-    \prop_if_in:NnTF \g__xsim_properties_prop {#2!#1!#3}
-      { \prg_return_true: }
-      { \prg_return_false: }
-  }
-\prg_generate_conditional_variant:Nnn \xsim_if_property_set:nnn
-  {nx,nnx,xx,nV}
-  {T,F,TF}
-
 % ----------------------------------------------------------------------------
 
-\prop_new:N \g__xsim_property_aliases_prop
 \seq_new:N \g__xsim_property_aliases_seq
 
 % #1: property
 \prg_new_conditional:Npnn \xsim_if_property_alias:n #1 {p,T,F,TF}
   {
-    \prop_if_in:NnTF \g__xsim_property_aliases_prop {#1}
+    \seq_if_in:NnTF \g__xsim_property_aliases_seq {#1}
       { \prg_return_true: }
       { \prg_return_false: }
   }
 
 % #1: property
 \cs_new:Npn \xsim_property_alias:n #1
-  { \prop_item:Nn \g__xsim_property_aliases_prop {#1} }
+  { \xsim_attribute_get:nn {#1} {alias} }
 
 % #1: property
 % #2: alias of
@@ -382,8 +396,7 @@
       {
         \xsim_verbose:n
           { Making~ property~ `#1'~ an~ alias~ of~ property~ `#2'. }
-        \prop_new:c {g__xsim_property_#1_alias_prop}
-        \prop_gput:Nnn \g__xsim_property_aliases_prop {#1} {#2}
+        \xsim_attribute_set:nnn {#1} {alias} {#2}
         \seq_gput_right:Nn \g__xsim_property_aliases_seq {#1}
       }
   }
@@ -408,8 +421,7 @@
     \xsim_if_property_set:nnxT {#1} {#2}
       { \xsim_property_alias:n {#3} }
       {
-        \prop_gput:cxx {g__xsim_property_#3_alias_prop}
-          { \xsim_get_property:nnn {#1} {#2} {#3} }
+        \xsim_attribute_set:nnx {alias:#1!#2} {#3}
           {
             \xsim_get_property:nnf {#1} {#2}
               { \xsim_property_alias:n {#3} }
@@ -433,18 +445,18 @@
 % #2: id
 % #3: property
 \cs_new:Npn \xsim_get_property:nnn #1#2#3
-  { \prop_item:Nn \g__xsim_properties_prop { #2 ! #1 ! #3 } }
+  { \xsim_attribute_get:nn {#1!#2} {#3} }
 \cs_generate_variant:Nn \xsim_get_property:nnn {nx,ne,xx,oo,no,nnf,nf,oof,nV}
 
 % #1: property
 % #2: value
 \cs_new:Npn \xsim_get_id_for_property:nn #1#2
-  { \prop_item:cn {g__xsim_property_#1_id_prop} {#2} }
+  { \xsim_attribute_get:nn {id:#1} {#2} }
 
 % #1: property
 % #2: value
 \cs_new:Npn \xsim_get_type_for_property:nn #1#2
-  { \prop_item:cn {g__xsim_property_#1_type_prop} {#2} }
+  { \xsim_attribute_get:nn {type:#1} {#2} }
 \cs_generate_variant:Nn \xsim_get_type_for_property:nn {nV}
 
 % #1: id or ID
@@ -512,7 +524,7 @@
 \cs_generate_variant:Nn \xsim_if_boolean_property:nnnF  {nV}
 
 \cs_new_protected:Npn \xsim_save_property:nnnN #1#2#3#4
-  { \prop_get:NnN \g__xsim_properties_prop {#2!#1!#3} #4 }
+  { \tl_set:No #4 { \cs:w __xsim_property_#2!#1!#3: \cs_end: } }
 \cs_generate_variant:Nn \xsim_save_property:nnnN {nx,xx}
 
 \cs_new_protected:Npn \xsim_gsave_property:nnnN #1#2#3#4
@@ -524,3 +536,5 @@
 
 % ----------------------------------------------------------------------------
 \file_input_stop:
+2020/03/09 - add meaningful error if a comma is missing in the property list
+2020/03/14 - performance optimizations
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.random.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.random.code.tex
index 422963792f3..cdd23e3a209 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.random.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.random.code.tex
@@ -94,7 +94,7 @@
 % #1: random list id
 % #2: sequence variable to set list from
 \cs_new_protected:Npn \xsim_save_random_list:nN #1#2
-  {
+  { % TODO: check if #2 is empty
     \xsim_random_list_if_exist:nF {#1}
       { \xsim_new_random_list:n {#1} }
     \xsim_random_list_if_empty:nT {#1}
@@ -103,6 +103,7 @@
     \xsim_add_property_to_aux:nn {random}
       { {#1} { \xsim_use_random_list:nn {#1} {,} } }
   }
+\cs_generate_variant:Nn \xsim_save_random_list:nN {x}
 
 % #1: collection
 % #2: number of items
@@ -142,7 +143,7 @@
               { \l__xsim_tmpa_int }
               \g__xsim_random_list_seq
           }
-        \xsim_save_random_list:nN
+        \xsim_save_random_list:xN
           { \int_to_alph:n { \g__xsim_random_list_id_int } }
           \g__xsim_random_list_seq
         \xsim_verbose:x
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.solutions.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.solutions.code.tex
index 2666d1aa864..0a691945085 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.solutions.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.solutions.code.tex
@@ -35,7 +35,7 @@
 \bool_new:N \l__xsim_printsolutions_conditions_bool
 \bool_new:N \l____xsim_this_condition_bool
 
-\prop_new:N \l__xsim_printsolutions_conditions_prop
+\seq_new:N \l__xsim_printsolutions_conditions_seq
 
 \int_new:N  \l_xsim_printsolutions_section_int
 \int_new:N  \l_xsim_printsolutions_chapter_int
@@ -194,7 +194,8 @@
 \cs_new_protected:Npn \xsim_declare_printsolutions_condition:nn #1#2
   {
     \bool_new:c {l__xsim_printsolutions_#1_condition_bool}
-    \prop_put:Nnn \l__xsim_printsolutions_conditions_prop {#1} {#2}
+    \seq_put_right:Nn \l__xsim_printsolutions_conditions_seq {#1}
+    \xsim_attribute_set:nnn {printsolutions} {#1} {#2}
   }
 
 \prg_new_conditional:Npnn \__xsim_printsolutions_if_condition:n #1 {T,F,TF}
@@ -218,11 +219,12 @@
   {
     \__xsim_printsolutions_condition_false:
     \bool_set_true:N \l____xsim_this_condition_bool
-    \prop_map_inline:Nn \l__xsim_printsolutions_conditions_prop
+    \seq_map_inline:Nn \l__xsim_printsolutions_conditions_seq
       {
         \bool_if:cT {l__xsim_printsolutions_##1_condition_bool}
           {
-            ##2 {#1} {#2} {#3}
+            \xsim_attribute_get:nn {printsolutions} {##1}
+              {#1} {#2} {#3}
               { }
               { \bool_set_false:N \l____xsim_this_condition_bool }
           }
@@ -409,3 +411,4 @@
 \file_input_stop:
 
 2020/02/23 - resolve bug #56
+2020/03/16 - performance optimizations
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.sty b/Master/texmf-dist/tex/latex/xsim/xsim.sty
index 8cd0f237960..79ab9b4b801 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.sty
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.sty
@@ -29,9 +29,9 @@
 
 \ExplSyntaxOn
 
-\tl_const:Nn \c_xsim_date_tl                 {2020/02/23}
+\tl_const:Nn \c_xsim_date_tl                 {2020/03/16}
 \tl_const:Nn \c_xsim_version_major_number_tl {0}
-\tl_const:Nn \c_xsim_version_minor_number_tl {18}
+\tl_const:Nn \c_xsim_version_minor_number_tl {19}
 \tl_const:Nn \c_xsim_version_subrelease_tl   {}
 \tl_const:Nx \c_xsim_version_number_tl
   {
@@ -57,6 +57,7 @@
 
 \bool_new:N \g__xsim_final_bool
 \bool_new:N \g__xsim_verbose_bool
+\bool_new:N \g__xsim_debug_bool
 \bool_new:N \g_xsim_clear_aux_bool
 \bool_new:N \g__xsim_write_to_file_bool
 \bool_new:N \g_xsim_use_aux_bool
@@ -67,6 +68,7 @@
   {
     final     .bool_gset:N         = \g__xsim_final_bool ,
     verbose   .bool_gset:N         = \g__xsim_verbose_bool ,
+    debug     .bool_gset:N         = \g__xsim_debug_bool ,
     clear-aux .bool_gset:N         = \g_xsim_clear_aux_bool ,
     no-files  .bool_gset_inverse:N = \g__xsim_write_to_file_bool ,
     no-files  .initial:n           = false ,
@@ -82,6 +84,7 @@
   {
     final     .code:n = \msg_error:nnn {xsim} {load-time-option} {final} ,
     verbose   .code:n = \msg_error:nnn {xsim} {load-time-option} {verbose} ,
+    debug     .code:n = \msg_error:nnn {xsim} {load-time-option} {debug} ,
     clear-aux .code:n = \msg_error:nnn {xsim} {load-time-option} {clear-aux} ,
     no-files  .code:n = \msg_error:nnn {xsim} {load-time-option} {no-files} ,
     use-aux   .code:n = \msg_error:nnn {xsim} {load-time-option} {use-aux} ,
diff --git a/Master/texmf-dist/tex/latex/xsim/xsim.templates.code.tex b/Master/texmf-dist/tex/latex/xsim/xsim.templates.code.tex
index 7644074be71..35bd173bba9 100644
--- a/Master/texmf-dist/tex/latex/xsim/xsim.templates.code.tex
+++ b/Master/texmf-dist/tex/latex/xsim/xsim.templates.code.tex
@@ -36,11 +36,21 @@
     I~ am~ using~ the~ template~ `#3'~ (template~ type~ `#1')~ instead.
   }
 
+\msg_new:nnn {xsim} {template-type-exists}
+  { The~ template~ type~ `#1'~ already~ exists~ \msg_line_context: }
+
+% ----------------------------------------------------------------------------
+\seq_new:N \l__xsim_template_types_seq
+
 % #1: template type
 \cs_new_protected:Npn \xsim_new_template_type:n #1
   {
-    \xsim_verbose:n { Declaring~ new~ template~ type~ `#1'. }
-    \prop_new:c {l__xsim_#1_template_prop}
+    \seq_if_in:NnTF \l__xsim_template_types_seq {#1}
+      { \msg_error:nnn {xsim} {template-type-exists} {#1} }
+      {
+        \xsim_verbose:n { Declaring~ new~ template~ type~ `#1'. }
+        \seq_put_right:Nn \l__xsim_template_types_seq {#1}
+      }
   }
 
 % #1: template type
@@ -50,12 +60,12 @@
   {
     \xsim_verbose:n { Defining~ new~ template~ `#2'~ of~ type~ `#1'. }
     \tl_new:c {l__xsim_template_#1_#2_setup_tl}
-    \prop_put:cnn {l__xsim_#1_template_prop} {#2} {#3}
+    \xsim_attribute_set:nnn {template::#1} {#2} {#3}
   }
 
 \prg_new_conditional:Npnn \xsim_if_template_exist:nn #1#2 {T,F,TF}
   {
-    \prop_if_in:cnTF {l__xsim_#1_template_prop} {#2}
+    \xsim_attribute_if_set:nnTF {template::#1} {#2}
       { \prg_return_true: }
       { \prg_return_false: }
   }
@@ -63,7 +73,7 @@
 % #1: template type
 % #2: template name
 \cs_new_protected:Npn \__xsim_get_template:nn #1#2
-  { \prop_item:cn {l__xsim_#1_template_prop} {#2} }
+  { \xsim_attribute_get:nn {template::#1} {#2} }
 
 % ----------------------------------------------------------------------------