Add step! to CommonSolve.jl

Project.toml

@@ -1,7 +1,7 @@
 name = "CommonSolve"
 uuid = "38540f10-b2f7-11e9-35d8-d573e4eb0ff2"
 authors = ["Chris Rackauckas <accounts@chrisrackauckas.com>"]
-version = "0.2.3"
+version = "0.2.4"
 
 [compat]
 julia = "1.6"

docs/src/index.md

@@ -1,8 +1,8 @@
 # CommonSolve.jl: The Common Solve Definition and Interface
 
-This holds the common `solve`, `init`, and `solve!` commands. By using the same definition,
+This holds the common `solve`, `init`, `solve!`, and `step!` commands. By using the same definition,
 solver libraries from other completely different ecosystems can extend the functions and thus
-not clash with SciML if both ecosystems export the `solve` command. The rules are that 
+not clash with SciML if both ecosystems export the `solve` command. The rules are that
 you must dispatch on one of your own types. That's it. No pirates.
 
 ## General recommendation
@@ -21,9 +21,16 @@ solve!(::SolverType) :: SolutionType
 ```
 
 where `ProblemType`, `SolverType`, and `SolutionType` are the types defined in
-your package.
+your package. 
 
-To avoid method ambiguity, the first argument of `solve`, `solve!`, and `init`
+In many cases, the `SolverType` is an object that is iteratively progressed to achieve the solution. In such cases, the `step!` function can be used:
+
+
+```julia
+step!(::SolverType, args...; kwargs...)
+```
+
+To avoid method ambiguity, the first argument of `solve`, `solve!`, `step!`, and `init`
 _must_ be dispatched on the type defined in your package.  For example, do
 _not_ define a method such as
 
@@ -37,6 +44,7 @@ init(::AbstractVector, ::AlgorithmType)
 CommonSolve.init
 CommonSolve.solve
 CommonSolve.solve!
+CommonSolve.step!
 ```
 
 ## Contributing
@@ -83,7 +91,7 @@ Pkg.status(;mode = PKGMODE_MANIFEST) # hide
 </details>
 ```
 ```@raw html
-You can also download the 
+You can also download the
 <a href="
 ```
 ```@eval
@@ -104,4 +112,4 @@ link = "https://github.com/SciML/"*name*".jl/tree/gh-pages/v"*version*"/assets/P
 ```
 ```@raw html
 ">project</a> file.
-```
+```

src/CommonSolve.jl

@@ -58,4 +58,15 @@ The `iter` type will be different for the different problem types.
 """
 function init end
 
+"""
+```julia
+CommonSolve.step!(iter, args...; kwargs...)
+```
+
+Progress the iterator object (the one returned by `CommonSolve.init`).
+The additional arguments typically describe how much to progress
+the iterator for, and are implementation-specific.
+"""
+function step! end
+
 end # module