private static bool ExactlyOnce(object[] args, TextBuffer output, BindingEnvironment env, MethodCallFrame predecessor, Step.Continuation k)
{
ArgumentCountException.Check("ExactlyOnce", 1, args);
TextBuffer finalOutput = output;
BindingList <LogicVariable> finalBindings = null;
State finalState = State.Empty;
MethodCallFrame finalFrame = predecessor;
bool failure = true;
var chain = Step.ChainFromBody("ExactlyOnce", args);
chain.Try(output, env,
(o, u, d, p) =>
{
failure = false;
finalOutput = o;
finalBindings = u;
finalState = d;
finalFrame = p;
return(true);
},
predecessor);
if (failure)
{
var failedCall = (Call)chain;
throw new CallFailedException(env.Resolve(failedCall.Task), env.ResolveList(failedCall.Arglist));
}
return(k(finalOutput, finalBindings, finalState, finalFrame));
}
/// <summary>
/// Attempt to run this task
/// </summary>
/// <param name="output">Output to which to write text</param>
/// <param name="env">Variable binding information</param>
/// <param name="k">Continuation to call at the end of this step's step-chain</param>
/// <param name="predecessor">Predecessor frame</param>
/// <returns>True if this steps, the rest of its step-chain, and the continuation all succeed.</returns>
public override bool Try(TextBuffer output, BindingEnvironment env, Continuation k, MethodCallFrame predecessor)
{
MethodCallFrame.CurrentFrame = env.Frame;
var target = env.Resolve(Task);
var arglist = env.ResolveList(Arglist);
return(CallTask(output, env, k, target, arglist, target, predecessor));
}
/// <inheritdoc /> public override bool Call(object[] arglist, TextBuffer output, BindingEnvironment env, MethodCallFrame predecessor, Step.Continuation k) => implementation(env.ResolveList(arglist), output, env, predecessor, k);
