error using yaml-cpp to get integer nested in key hierarchy - yaml-cpp

Question

Initial Question
I have a config.yaml that has structure similar to
some_other_key: 34
a:
b:
c:
d: 3
I thought I could do
YAML::Node config = YAML::LoadFile(config_filename.c_str());
int x = config["a"]["b"]["c"]["d"].as<int>();
but I get
terminate called after throwing an instance of
'YAML::TypedBadConversion<int>'
what(): bad conversion
How do I descend through my config.yaml to extract a value like this? I also get that same exception if I mistype one of the keys in the path, so I can't tell from the error if I am accidentally working with a null node or if there is a problem converting a valid node's value to int
Follow up After First Replies
Thank you for replying! Maybe it is an issue with what is in the config.yaml? Here is a small example to reproduce,
yaml file: config2.yaml
daq_writer:
num: 3
num_per_host: 3
hosts:
- local
datasets:
small:
chunksize: 600
Python can read it:
Incidentally, I am on linux on rhel7, but from a python 3.6 environment, everything looks good:
$ python -c "import yaml; print(yaml.load(open('config2.yaml','r')))"
{'daq_writer': {'num_per_host': 3, 'num': 3, 'datasets': {'small': {'chunksize': 600}}, 'hosts': ['local']}}
C++ yaml-cpp code
The file yamlex.cpp:
#include <string>
#include <iostream>
#include "yaml-cpp/yaml.h"
int main() {
YAML::Node config = YAML::LoadFile("config2.yaml");
int small_chunksize = config["daq_writer"]["datasets"]["smal"]["chunksize"].as<int>();
}
When I compile and run this, I get:
(lc2) psanagpu101: ~/rel/lc2-hdf5-110 $ c++ --std=c++11 -Iinclude -Llib -lyaml-cpp yamlex.cpp
(lc2) psanagpu101: ~/rel/lc2-hdf5-110 $ LD_LIBRARY_PATH=lib ./a.out
terminate called after throwing an instance of 'YAML::TypedBadConversion<int>'
what(): bad conversion
Aborted (core dumped)
(lc2) psanagpu101: ~/rel/lc2-hdf5-110 $ gcc --version
gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-4)
I have been able to read top level keys, like the some_other_key that I referenced above, but I got an error when I went after this nested key. Good to know that syntax works!

Answer 1

You have a typo in your keys: instead of "small", you wrote "smal".