lambda style

Former-commit-id: 5a56c0d8d985c4ee020c70de9b2bfb932ef21748

style-guidelines.md

@@ -94,7 +94,12 @@ new pair of .h/.cpp files with this sub-function.
 
 If encapsulation in a separate file is not possible or does not make sense,
 then avoid crowding the namespace by creating lambda functions within the
-function implmentation.
+function implementation.
+
+These lambda functions must still be documented with clear [input and output
+arguments](#headerdocumentation). Avoid using full capturing of all automatic
+variables: do not use `[&]` or `[=]`. Rather specify each captured variable
+individually.
 
 ### Avoid "helper" classes
 
@@ -104,7 +109,6 @@ pass "basic types" directly. The price we pay is long function interfaces, but
 this increases code reuse dramatically. A "basic type" in our context is a
 Eigen type, stl type, or basic C type.
 
-
 ## Header Documentation
 
 Each function prototype should be well documented in its corresponding .h