Document eval_string

Author: romainbrenguier

src/solvers/refinement/string_builtin_function.cpp

@@ -8,7 +8,9 @@
 
 #include "string_constraint_generator.h"
 
-/// Get the valuation of the string, given a valuation
+/// Given a function `get_value` which gives a valuation to expressions, attempt
+/// to find the current value of the array `a`. If the valuation of some
+/// characters are missing, then return an empty optional.
 static optionalt<std::vector<mp_integer>> eval_string(
   const array_string_exprt &a,
   const std::function<exprt(const exprt &)> &get_value);