Add WhereWithVars

doc/ref/debug.xml

@@ -19,7 +19,8 @@ Probably the most important debugging tool in ⪆ is the break loop
 an <Ref Func="Error"/> statement into your code or by hitting Control-C.
 In the break loop one can inspect variables, stack traces and issue 
 commands as usual in an interactive &GAP; session. See also the
-<Ref Func="DownEnv"/>, <Ref Func="UpEnv"/> and <Ref Func="Where"/>
+<Ref Func="DownEnv"/>, <Ref Func="UpEnv"/>, <Ref Func="Where"/> and
+<Ref Func="WhereWithVars"/>
 functions.
 <P/>
 Sections&nbsp;<Ref Sect="sect:ApplicableMethod"/>

doc/ref/mloop.xml

@@ -739,14 +739,16 @@ is an example in the ⪆ code where the idea is actually used.
 <P/>
 <ManSection>
 <Func Name="Where" Arg='nr'/>
-
+<Func Name="WhereWithVars" Arg='nr'/>
 <Description>
 <Index Subkey="GAP3 name for Where">Backtrace</Index>
 <Index>Stack trace</Index>
 shows the last <A>nr</A> commands on the execution stack during whose execution
 the error occurred. If not given, <A>nr</A> defaults to 5. (Assume, for the
 following example, that after the last example <Ref Func="OnBreak"/>
-has been set back to its default value.)
+has been set back to its default value.). <Ref Func="WhereWithVars"/> acts the
+same as <Ref Func="Where"/> while also showing the arguments and local
+variables of each function.
 <P/>
 <Log><![CDATA[
 gap> StabChain(SymmetricGroup(100)); # After this we typed ^C  

lib/error.g

@@ -59,15 +59,60 @@ end);
 
 ErrorLVars := fail;
 
-BIND_GLOBAL("WHERE", function( context, depth, outercontext)
-    local   bottom,  lastcontext,  f;
+# In this method the line hint changes in every PrintTo are balanced, because at the moment
+# PrintTo(ERROR_OUTPUT,...) resets the indentation level every time it is called.
+# If/when this is fixed, the indendation in this function could be simplified
+BIND_GLOBAL("PRETTY_PRINT_VARS", function(context)
+    local vars, i, argcount, val;
+    vars := ContentsLVars(context);
+    if not IsRecord(vars) then
+        return;
+    fi;
+
+    argcount := ABS_RAT(NumberArgumentsFunction(vars.func));
+    PrintTo(ERROR_OUTPUT, "\>\>\n\<\<arguments:");
+    if argcount = 0 then
+        PrintTo(ERROR_OUTPUT, " <none>");
+    else
+        for i in [1..argcount] do
+            if IsBound(vars.values[i]) then
+                val := vars.values[i];
+            else
+                val := "<unassigned>";
+            fi;
+            PrintTo(ERROR_OUTPUT, "\>\>\>\>\n", vars.names[i], " :=\>\> ", val, "\<\<\<\<\<\<");
+        od;
+    fi;
+
+    PrintTo(ERROR_OUTPUT, "\>\>\n\<\<local variables:");
+    if argcount = Length(vars.names) then
+        PrintTo(ERROR_OUTPUT, " <none>");
+    else
+        for i in [argcount+1..Length(vars.names)] do
+            if IsBound(vars.values[i]) then
+                val := vars.values[i];
+            else
+                val := "<unassigned>";
+            fi;
+            PrintTo(ERROR_OUTPUT, "\>\>\>\>\n", vars.names[i], " :=\>\> ", val, "\<\<\<\<\<\<");
+        od;
+    fi;
+    PrintTo(ERROR_OUTPUT,"\n");
+end);
+
+BIND_GLOBAL("WHERE", function(context, depth, outercontext, showlocals)
+    local bottom, lastcontext, f, args;
     if depth <= 0 then
         return;
     fi;
     bottom := GetBottomLVars();
     lastcontext := outercontext;
     while depth > 0  and context <> bottom do
         PRINT_CURRENT_STATEMENT(ERROR_OUTPUT, context);
+        if showlocals then
+            PRETTY_PRINT_VARS(context);
+        fi;
+
         PrintTo(ERROR_OUTPUT, " called from\n");
         lastcontext := context;
         context := ParentLVars(context);
@@ -83,22 +128,38 @@ BIND_GLOBAL("WHERE", function( context, depth, outercontext)
 end);
 
 
-BIND_GLOBAL("Where", function(arg)
+BIND_GLOBAL("WHERE_INTERNAL", function(depth, showlocals)
+    if ErrorLVars = fail or ErrorLVars = GetBottomLVars() then
+        PrintTo(ERROR_OUTPUT, "not in any function ");
+    else
+        WHERE(ParentLVars(ErrorLVars), depth, ErrorLVars, showlocals);
+    fi;
+    PrintTo(ERROR_OUTPUT, "at ", INPUT_FILENAME(), ":", INPUT_LINENUMBER(), "\n");
+end);
+
+BIND_GLOBAL("WhereWithVars", function(arg)
     local   depth;
     if LEN_LIST(arg) = 0 then
         depth := 5;
     else
         depth := arg[1];
     fi;
-
-    if ErrorLVars = fail or ErrorLVars = GetBottomLVars() then
-        PrintTo(ERROR_OUTPUT, "not in any function ");
+
+    WHERE_INTERNAL(depth, true);
+end);
+
+BIND_GLOBAL("Where", function(arg)
+    local   depth;
+    if LEN_LIST(arg) = 0 then
+        depth := 5;
     else
-        WHERE(ParentLVars(ErrorLVars),depth, ErrorLVars);
+        depth := arg[1];
     fi;
-    PrintTo(ERROR_OUTPUT, "at ",INPUT_FILENAME(),":",INPUT_LINENUMBER(),"\n");
+
+    WHERE_INTERNAL(depth, false);
 end);
 
+
 OnBreak := Where;
 
 #OnBreak := function() 

tst/testspecial/backtrace.g

@@ -5,72 +5,101 @@ f := function()
 end;
 f();
 Where();
+WhereWithVars();
 quit;
 
 
 f:=function() if true = 1/0 then return 1; fi; return 2; end;;
 f();
 Where();
+WhereWithVars();
 quit;
 
 
 f:=function() local x; if x then return 1; fi; return 2; end;;
 f();
 Where();
+WhereWithVars();
 quit;
 
 
 f:=function() if 1 then return 1; fi; return 2; end;;
 f();
 Where();
+WhereWithVars();
 quit;
 
 
 f:=function() if 1 < 0 then return 1; elif 1 then return 2; fi; return 3; end;;
 f();
 Where();
+WhereWithVars();
 quit;
 
 
 f:=function() while 1 do return 1; od; return 2; end;;
 f();
 Where();
+WhereWithVars();
 quit;
 
 
 f:=function() local i; for i in 1 do return 1; od; return 2; end;;
 f();
 Where();
+WhereWithVars();
 quit;
 
 
 f:=function() local i; for i in true do return 1; od; return 2; end;;
 f();
 Where();
+WhereWithVars();
 quit;
 
+f:=function(x) local i,j; for i in true do return 1; od; return 2; end;;
+f([1,2,3]);
+Where();
+WhereWithVars();
+quit;
+
+f:=function(x) local i,j; Unbind(x); for i in true do return 1; od; return 2; end;;
+f([1,2,3]);
+Where();
+WhereWithVars();
+quit;
+
+f:=function(x) local i,j; Unbind(x); j := 4; for i in true do return 1; od; return 2; end;;
+f([1,2,3]);
+Where();
+WhereWithVars();
+quit;
 
 f:=function() local x; repeat x:=1; until 1; return 2; end;;
 f();
 Where();
+WhereWithVars();
 quit;
 
 
 f:=function() local x; Assert(0, 1); return 2; end;;
 f();
 Where();
+WhereWithVars();
 quit;
 
 
 f:=function() local x; Assert(0, 1, "hello"); return 2; end;;
 f();
 Where();
+WhereWithVars();
 quit;
 
 # Verify issue #2656 is fixed
 l := [[1]];; f := {} -> l[2,1];;
 f();
 Where();
+WhereWithVars();
 quit;
 
 # verify issue #1373 is fixed