On 10 August 2015 at 20:16, Thompson, David <dthompson2@worcester.edu> wrote:
I believe this is because the return value of
'xorg-configuration-file' is a monadic value, and thus it needs to
"unwrapped" in order to pass the configuration file to
'xorg-start-command'.

Try this:

    (mlet %store-monad ((config
                         (xorg-configuration-file #:drivers '("radeon" "vesa")
                                                  #:resolutions '((1366 768)
                                                                  (1024 768)))))
      (slim-service #:startx (xorg-start-command #:configuration-file config)))

I've tried this

  (services (cons* 
(mlet %store-monad ((config
  (xorg-configuration-file #:drivers '("radeon" "vesa")
                           #:resolutions '((1366 768) (1024 768)))))
(slim-service #:startx (xorg-start-command 
#:configuration-file config)))
                   ;;%desktop-services
                   %base-services))

But still failed

substitute: updating list of substitutes from 'http://hydra.gnu.org'... 100.0%
The following derivations will be built:
   /gnu/store/w95zdcd070xgpgbldfmij9b7m0v3px9g-system.drv
   /gnu/store/11vwx7pidb683ip9p9r0xg24h2d96pxf-grub.cfg.drv
   /gnu/store/4fmkwv683rhfc2397255s54nwggxfkmw-slim.cfg.drv
   /gnu/store/sxp6xg8wa71klwafyxdj8iwymphla81s-dmd.conf.drv
   /gnu/store/1d7bw0ga0f23rbb40zi45ql9w96nx2b8-boot.drv
   /gnu/store/vc4vyxqh92yfz32hsvc713kxgy89h2sj-system.drv
   /gnu/store/l7a4v3izzcwa681sg7pcq4bhllg4l3j4-slim.cfg.drv
   /gnu/store/3ibsmapzd65rj30a0mxkd74qv36rprmc-dmd.conf.drv
   /gnu/store/1nawmbn0qnafr5inq14xil9cw1x16sns-boot.drv
ERROR: In procedure primitive-load:
ERROR: In procedure scm_lreadr: /gnu/store/1d4h26j8w7vbmybv09b9839drf1i96x4-slim.cfg-builder:1:159: Unknown # object: #\<
builder for `/gnu/store/l7a4v3izzcwa681sg7pcq4bhllg4l3j4-slim.cfg.drv' failed with exit code 1
cannot build derivation `/gnu/store/3ibsmapzd65rj30a0mxkd74qv36rprmc-dmd.conf.drv': 1 dependencies couldn't be built
cannot build derivation `/gnu/store/1nawmbn0qnafr5inq14xil9cw1x16sns-boot.drv': 1 dependencies couldn't be built
cannot build derivation `/gnu/store/w95zdcd070xgpgbldfmij9b7m0v3px9g-system.drv': 1 dependencies couldn't be built
guix system: error: build failed: build of `/gnu/store/w95zdcd070xgpgbldfmij9b7m0v3px9g-system.drv' failed

Maybe I need to add some (use modules ...) statements? Where should I put (mlet ...) statement?

Dmitry