update the readme

README.md

@@ -2,15 +2,23 @@
 Circom witness generators
 -------------------------
 
-This piece of software takes the computation graph files generated by 
+The original idea behind this small project was to take the "computation graph" 
-[`circom-witnesscalc`](https://github.com/iden3/circom-witnesscalc),
+files generated by  [`circom-witnesscalc`](https://github.com/iden3/circom-witnesscalc),
 and either interprets or compiles them to various algebra backends.
 
+While this is quite straightforward in principle, and seems to work on small
+examples, it turns out that `circom-witnesscalc` itself is completely broken,
+in the sense that it doesn't seem to be able to handle nontrivial circuits using any 
+kind of meaningful metaprogramming (that being the only thing which makes `circom` 
+borderline useful).
+
+And this doesn't look fixable without something like a full rewrite of `circom-witnesscalc` (?).
+
 ### Implementation status
 
 Compiler (in Haskell):
 
-- [x] parsing the graph files
+- [x] parsing the graph file
 - [x] naive interpreter
 - [ ] constantine backend
 - [ ] zikkurat backend
@@ -18,7 +26,7 @@ Compiler (in Haskell):
 
 Nim witness generator:
 
-- [x] parsing the graph files
+- [x] parsing the graph file
 - [ ] generating the witness
 - [ ] proper error handling