unison/docs/runtime-calling-conventions.markdown

### Lambda
- called with arguments in declared order.
- whenever a lambda is called, it takes itself as `rec`
- it evaluates the body passing the bound lambda parameters on the stack

### Computation
- bound variables passed on stack with innermost scope closest to index 0
- "rec" is passed as well (?)
- evaluations in nontail positions need to catch handle TC because their "frame"
  has more work and shouldn't be thrown away; evaluations in tail positions can
  throw their tailcalls upward and discard their frame
- let1/letrec evaluate the bindings with the existing stack (bound variables in their scope);
    body is called with bindings prepended to stack
- compilevar returns rec if its name matches currentRec,
    otherwise looks up a value on the bindings stack
- compilelambda returns a computation that will produce a lambda when evaluated
- apply
  - if fn name matches currentRec, then staticRecCall
    - staticRecTailCall
      - throw selfTailCall with evaluated args (seems like this would not do anything) (?)
    - staticRecNonTailCall
      - call (rec: Lambda) with evaluated args
      - a SelfCall exception should never escape the wrapper lambda 
  - else compile fn
    - if compiled fn is Return(Lambda)
      - staticTailCall
        - throw tailcall with fn
      - staticNonTailCall
        - call fn with rec = fn
    - else compiled fn is not yet a lambda, and needs to be evaluated again (at least once)
      - dynamicTailCall
        - eval mkFn and assume it produces a lambda (it should)
        - throw tailcall with lambda and eval'd args
      - dynamicNontailCall
        - eval mkFn and assume it produces a lambda (it should!)
        - call lambda with evaluated args
### Tail calls
tailcall throws an exception with the target function & args
selfTailCall throws a tailcall with null(implied?) function

when a tailcall exception is caught, we enter a while loop which calls the
 target function and continues to catch tail calls until the target function
 is null.

note that the selftailcall begins with null. (?) don't understand

### annotated bounds