An 'a t is a term that produces a value of type 'a.

Information about operations hidden behind a bind.

active x is a term indicating that the result is not determined yet.

return x is a term that immediately succeeds with x.

• parameter label

  Label the constant in the diagrams.

fail m is a term that immediately fails with message m.

state t always immediately returns a successful result giving the current state of t.

• parameter hidden

  If true, don't show a separate node for this on the diagrams.

catch t successfully returns Ok x if t evaluates successfully to x, or successfully returns Error e if t fails with error e. If t is active then catch t will be active too.

• parameter hidden

  If true, don't show a separate node for this on the diagrams.

ignore_value x is map ignore x.

of_output x is a returned, failed or active term.

map f x is a term that runs x and then transforms the result using f.

The optional equality function ?eq defaults to physical equality. When f produces an updated result following a change in x, the equality function will be called with the previous and the new value eq b_old b_new: returning true indicates that the change can be ignored and should not propagate further down the pipeline.

map_error f x is a term that runs x and then transforms the error string (if any) using f.

pair a b is the pair containing the results of evaluating a and b (in parallel).

list_map (module T) f xs adds f to the end of each input term and collects all the results into a single list.

• parameter T

  Used to display labels for each item, and to avoid recreating pipelines unnecessarily.

• parameter collapse_key

  If given, each element is wrapped with collapse.

• parameter label

  Label the list in the diagrams.

Like list_map but for the simpler case when the result is unit.

• parameter label

  Label the list in the diagrams.

list_seq x evaluates to a list containing the results of evaluating each element in x, once all elements of x have successfully completed.

option_map f x is a term that evaluates to Some (f y) if x evaluates to Some y, or to None otherwise.

• parameter label

  Label the optional in the diagrams.

Like option_map but for the simpler case when the result is unit.

• parameter label

  Label the list in the diagrams.

option_seq None is Current.return None and option_seq (Some x) is Current.map some x. This is useful for handling optional arguments that are currents.

all xs is a term that succeeds if every term in xs succeeds.

all xs is a term that succeeds if every term in xs succeeds. The labels are used if some terms fail, to indicate which ones are failing.

gate ~on:ctrl x is the same as x, once ctrl succeeds.

Note: gate does not delay x; it only delays whatever you put after the gate. e.g.

let binary = build src in
let tests_ok = test binary in
binary |> gate ~on:tests_ok |> deploy

cutoff ~eq x is the same as x, but changes to x that are equal according to eq do not propagate further down. It should be used when values of type 'a have a precise definition of equality to avoid triggering redundant work.

collapse ~key ~value ~input t is a term that behaves just like t, but when shown in a diagram it can be expanded or collapsed. When collapsed, it is shown as "input -> +" and the user can expand it to show t instead. The idea is that input is a dependency of t and the "+" represents everything in t after that. key and value are used as the parameters (e.g. in a URL) to control whether this is expanded or not. For example collapse ~key:"repo" ~value:"mirage/mirage-www" ~input:repo (process repo) Note: list_map ~collapse_key provides an easy way to use this.

collapse_list ~key ~value ~input t is a term that behaves just like t list, but when shown in a diagram it can be expanded or collapsed.

with_context ctx f is the term f (), where f is evaluated in context ctx. This means that ctx will be treated as an input to all terms created by f in the diagrams.

bind f x is a term that first runs x to get y and then behaves as the term f y. Static analysis cannot look inside the f function until x is ready, so using bind makes static analysis less useful. You can use the info argument to provide some information here.

primitive ~info f x is a term that evaluates f on each new value of x. This is used to provide the primitive operations, which can then be combined using the other combinators in this module. info is used to label the operation in the diagram.

component name is used to annotate binds, so that the system can show a name for the operations hidden inside the bind's function. name is used as the label for the bind in the generated dot diagrams. For convenience, name can also be a format string.

observe x evaluates the current state of term x. A `Blocked value occurs when the term failed because an upstream dependency errored.