diff --git a/c/todo.txt b/c/todo.txt
index f99d31fa3..00725adcf 100644
--- a/c/todo.txt
+++ b/c/todo.txt
@@ -59,11 +59,46 @@ FIX:
 * mlr --oxtab put -q @v = $*; end {emit @v } ./reg_test/input/abixy-het
   --> has 10 fields -- not desired.
 
-* basenaming syntax for subselector emits
-
 * mlr --opprint put -q '@v[NR]=$*; end{emit @v[1],"X"}' ../data/small
   --> runs out of data and should not
 
+* do more oosvar experiments before finalizing mlr4
+
+! tri-split-null wrong-looking:
+  $ mlr put -q @sum += $x; end{emit @sum} ./reg_test/input/abixy-het
+  sum=
+
+  $ mlr put -q '@sum += $x; @sumtype = typeof(@sum); @xtype = typeof($x); emitf @sumtype, @xtype, @sum; end{emit @sum}' ./reg_test/input/abixy-het
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=0.346790
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=1.105470
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=1.310073
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=1.691473
+  sumtype=MT_VOID,xtype=MT_ABSENT,sum=
+  sumtype=MT_VOID,xtype=MT_FLOAT,sum=
+  sumtype=MT_VOID,xtype=MT_FLOAT,sum=
+  sumtype=MT_VOID,xtype=MT_FLOAT,sum=
+  sumtype=MT_VOID,xtype=MT_FLOAT,sum=
+  sumtype=MT_VOID,xtype=MT_FLOAT,sum=
+  sum=
+
+  mlr put -q '@sum += $x; @sumtype = typeof(@sum); @xtype = typeof($x); emitf @sumtype, @xtype, @sum; end{emit @sum}' ./reg_test/input/abixy
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=0.346790
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=1.105470
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=1.310073
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=1.691473
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=2.264762
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=2.791888
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=3.403672
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=4.002226
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=4.033668
+  sumtype=MT_FLOAT,xtype=MT_FLOAT,sum=4.536294
+  sum=4.536294
+
+----------------------------------------------------------------
+IMPLEMENT:
+
+* basenaming syntax for subselector emits
+
 * mlr put -q '@v[NR]=$*; emit @v' ../data/small
   --> currently has field names v:a,v:x, etc -- think about a simpler option
 
@@ -77,46 +112,13 @@ FIX:
 
 * cli-parameterize the joinchar (:)
 
-* do more oosvar experiments before finalizing mlr4
-
 ----------------------------------------------------------------
 UT:
 
-* define/test behavior for null-valued filter/gate
+* define/test behavior for null-valued filter / cond-block
 * evolve & extend the existing UTs
-* ut/t-mlhm: assert on contents of sllv of plrec
 w basenaming syntax for subselector emits (once it exists!)
 
-! tri-split-null wrong-looking:
-  $ mlr put -q @sum += $x; end{emit @sum} ./reg_test/input/abixy-het
-  sum=
-
-  $ mlr put -q '@sum += $x; @t = typeof(@sum); @u = typeof($x); emitf @t, @u, @sum; end{emit @sum}' ./reg_test/input/abixy-het
-  t=MT_FLOAT,u=MT_FLOAT,sum=0.346790
-  t=MT_FLOAT,u=MT_FLOAT,sum=1.105470
-  t=MT_FLOAT,u=MT_FLOAT,sum=1.310073
-  t=MT_FLOAT,u=MT_FLOAT,sum=1.691473
-  t=MT_VOID,u=MT_ABSENT,sum=
-  t=MT_VOID,u=MT_FLOAT,sum=
-  t=MT_VOID,u=MT_FLOAT,sum=
-  t=MT_VOID,u=MT_FLOAT,sum=
-  t=MT_VOID,u=MT_FLOAT,sum=
-  t=MT_VOID,u=MT_FLOAT,sum=
-  sum=
-
-  mlr put -q '@sum += $x; @t = typeof(@sum); @u = typeof($x); emitf @t, @u, @sum; end{emit @sum}' ./reg_test/input/abixy
-  t=MT_FLOAT,u=MT_FLOAT,sum=0.346790
-  t=MT_FLOAT,u=MT_FLOAT,sum=1.105470
-  t=MT_FLOAT,u=MT_FLOAT,sum=1.310073
-  t=MT_FLOAT,u=MT_FLOAT,sum=1.691473
-  t=MT_FLOAT,u=MT_FLOAT,sum=2.264762
-  t=MT_FLOAT,u=MT_FLOAT,sum=2.791888
-  t=MT_FLOAT,u=MT_FLOAT,sum=3.403672
-  t=MT_FLOAT,u=MT_FLOAT,sum=4.002226
-  t=MT_FLOAT,u=MT_FLOAT,sum=4.033668
-  t=MT_FLOAT,u=MT_FLOAT,sum=4.536294
-  sum=4.536294
-
 ----------------------------------------------------------------
 DOC:
 
@@ -143,9 +145,10 @@ HYG:
 ================================================================
 OOSVAR EXPERIMENTS:
 
-* what userspace data structures (and maybe new functions? keywords/control?) would be needed for:
 * check for functionality -- this is my best chance to do a full-featuredness check for oosvars & emit
 * also do timing comparisons
+
+* list:
   - bootstrap?
   - count-distinct?
   - cut?
diff --git a/c/unit_test/test_mlhmmv.c b/c/unit_test/test_mlhmmv.c
index cc18d4103..f27586fbf 100644
--- a/c/unit_test/test_mlhmmv.c
+++ b/c/unit_test/test_mlhmmv.c
@@ -190,67 +190,6 @@ static char* test_depth_errors() {
 }
 
 // ----------------------------------------------------------------
-// $ mlr put -q '@sum[$a][$b][$i]=$x; end{dump}' ../data/small | mlr --ijson --oxtab cat
-// sum:pan:pan:1=0.346790
-// sum:pan:wye:10=0.502626
-// sum:eks:pan:2=0.758680
-// sum:eks:wye:4=0.381399
-// sum:eks:zee:7=0.611784
-// sum:wye:wye:3=0.204603
-// sum:wye:pan:5=0.573289
-// sum:zee:pan:6=0.527126
-// sum:zee:wye:8=0.598554
-// sum:hat:wye:9=0.031442
-
-
-// $ mlr put -q '@sum[$a][$b][$i]=$x; end{emit @sum}' ../data/small
-// sum:pan:pan:1=0.346790
-// sum:pan:wye:10=0.502626
-// sum:eks:pan:2=0.758680
-// sum:eks:wye:4=0.381399
-// sum:eks:zee:7=0.611784
-// sum:wye:wye:3=0.204603
-// sum:wye:pan:5=0.573289
-// sum:zee:pan:6=0.527126
-// sum:zee:wye:8=0.598554
-// sum:hat:wye:9=0.031442
-
-// $ mlr put -q '@sum[$a][$b][$i]=$x; end{emit @sum, "a"}' ../data/small
-// a=pan,sum:pan:1=0.346790
-// a=pan,sum:wye:10=0.502626
-// a=eks,sum:pan:2=0.758680
-// a=eks,sum:wye:4=0.381399
-// a=eks,sum:zee:7=0.611784
-// a=wye,sum:wye:3=0.204603
-// a=wye,sum:pan:5=0.573289
-// a=zee,sum:pan:6=0.527126
-// a=zee,sum:wye:8=0.598554
-// a=hat,sum:wye:9=0.031442
-
-// $ mlr put -q '@sum[$a][$b][$i]=$x; end{emit @sum, "a","b"}' ../data/small
-// a=pan,b=pan,sum:1=0.346790
-// a=pan,b=wye,sum:10=0.502626
-// a=eks,b=pan,sum:2=0.758680
-// a=eks,b=wye,sum:4=0.381399
-// a=eks,b=zee,sum:7=0.611784
-// a=wye,b=wye,sum:3=0.204603
-// a=wye,b=pan,sum:5=0.573289
-// a=zee,b=pan,sum:6=0.527126
-// a=zee,b=wye,sum:8=0.598554
-// a=hat,b=wye,sum:9=0.031442
-
-// $ mlr put -q '@sum[$a][$b][$i]=$x; end{emit @sum, "a","b","i"}' ../data/small
-// a=pan,b=pan,i=1,sum=0.346790
-// a=pan,b=wye,i=10,sum=0.502626
-// a=eks,b=pan,i=2,sum=0.758680
-// a=eks,b=wye,i=4,sum=0.381399
-// a=eks,b=zee,i=7,sum=0.611784
-// a=wye,b=wye,i=3,sum=0.204603
-// a=wye,b=pan,i=5,sum=0.573289
-// a=zee,b=pan,i=6,sum=0.527126
-// a=zee,b=wye,i=8,sum=0.598554
-// a=hat,b=wye,i=9,sum=0.031442
-
 static char* test_mlhmmv_to_lrecs() {
 	printf("================================================================\n");
 	mlhmmv_t* pmap = mlhmmv_alloc();