futhark [options...] infile
This is a Futhark compiler development tool, intentionally undocumented and intended for use in developing the Futhark compiler, not for programmers writing in Futhark. To compile Futhark code, use one of the compilers, e.g. futhark-c or futhark-opencl.
For documentation on the Futhark language itself, see:
http://futhark.readthedocs.iofuthark-c(1), futhark-opencl(1)