HSD-Fortran Documentation
HSD-Fortran is a lightweight, dependency-free Human-friendly Structured Data (HSD) parser for Fortran.
HSD is a data format similar to JSON and YAML, but designed to minimize the effort for humans to read and write it. It was originally developed as the input format for DFTB+.
Features
Parsing HSD files into a tree structure with comprehensive error reporting
Serialization of data structures back to HSD format
Include support with cycle detection (
<<+for HSD,<<<for text)Path-based accessors for convenient data retrieval (e.g.,
"section/subsection/value")Type introspection to query node types before access
Tree operations including merge, clone, and recursive traversal
Quick Start
program example
use hsd
implicit none
type(hsd_node_t), target :: root
type(hsd_access_t) :: access
type(hsd_error_t), allocatable :: error
integer :: max_steps
real(dp) :: temperature
! Load HSD file
call hsd_load_file("input.hsd", root, error)
if (allocated(error)) then
call error%print()
stop 1
end if
! Access values via the access object
call access%init(root)
call access%get("Driver/MaxSteps", max_steps)
call access%get("Hamiltonian/DFTB/Temperature", temperature)
! Modify and save
call access%set("Driver/MaxSteps", 200)
call hsd_dump(root, "output.hsd")
if (access%has_errors()) call access%print_errors()
end program example
Example HSD input:
Driver = ConjugateGradient {
MaxSteps = 100
}
Hamiltonian = DFTB {
SCC = Yes
Temperature [Kelvin] = 300.0
}