fparser/README.md

# A Modern Fortran-based Parser

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## Get the code
  The parser uses a modified libfdf library. This is included in this repository as a submodule. To clone the entire project, do

  `git clone --recurse-submodules https://github.com/TREX-CoE/iof08.git`


## Compilation
  The project contains two folders (a) modified-libfdf and (b) parser.

  - Compile and install the modified-libfdf using the following set of commands
    ```Console
        ./configure --prefix=/usr/local FC=ifort CC=icc
        make
        sudo make install
        make check
    ```
  - In the parser folder, link the modified libfdf library with the interface Fortran file.
  ```

## Integrate parser in your code



### Features of the parser (including inheritance from libfdf)

- Include another input file for parser to read using:

` %include    global.inp`

- Include a data file for parser to read using:

` load label filename`

Here, depending upon the label, parser will provide the filename. For example,

` load basis cc-pvtz.gbs`

- Read molecular coordinates directly from the input file using 

```perl
%block molecule 
12
 #benzene comment
 C    0.00000    1.40272  0
 H    0.00000    2.49029  0
 C   -1.21479    0.70136  0
 H   -2.15666    1.24515  0
 C   -1.21479   -0.70136  0
 H   -2.15666   -1.24515  0
 C    0.00000   -1.40272  0
 H    0.00000   -2.49029  0
 C    1.21479   -0.70136  0
 H    2.15666   -1.24515  0
 C    1.21479    0.70136  0
 H    2.15666    1.24515  0
%endblock
```

- Read molecular coordinates from an external .xyz file using 

` %block molecule < caffeine.xyz `


- Group certain keywords using the %module construct

```perl
%module DMC
    tau     =   0.04
    etrial  = -15 Ha
%endmodule
```

- Logical variables accept true, TRUE, T, 1, .true. as valid keywords for true
` optimize_wavefunction 	true`




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