checkArgument

Description:

public static Result<bool,Error> checkArgument (bool cond, string message)

Checks argument preconditions.

Example:

    var result = Preconditions.checkArgument (name.length > 0, "name must not be empty");
    if (result.isError ()) {
        return;
    }

cond	condition that must be true.
message	error message when condition is false.

Result.ok(true) on success, or Result.error(PreconditionError.INVALID_ARGUMENT) when condition is false.