feature_index.cpp file gives error when installing CRF++ V0.51

[Apurv3377]

Hello,

I have been trying to install ParsCit for my thesis work. For that I am following step from INSTALL file. I am facing a problem when I am installing CRF++ V0.51. Can someone please guide me here?

Problem (Steps to reproduce):

feature_index.cpp:174:60: error: cannot bind rvalue reference of type 'int&&' to lvalue of type 'int'
  174 |         old2new.insert(std::make_pair<int, int>(it->second.first, new_maxid));     
```                               ~~~~~~~~~~~^~~~~

**Steps Followed:**

1. Download the source code from https://github.com/knmnyn/ParsCit and unzip it.
2. Install c++ compiler (sudo apt install g++)
3. Install ruby (sudo apt install ruby-full)
4. Install Perl modules from CPAN mentioned in INSTALL file.
5. Install crfpp (verison 0.51) from source.
    5.1 Get into the crfpp directory
    5.2 Download v0.51 from [this link](https://taku910.github.io/crfpp/#source)
    5.3 Unzip the tar file
    5.4 Get into the CRF++ directory
    5.5 ./configure
    5.6 make / make clean / make.

[knmnyn]

Hi ParsCit is not regularly supported anymore as we have more recent toolkits that use neural approaches that outperform this method. You're welcomed to check out NeuralParsCit or SciWING as replacements.