notes

Author: Bost

notes/cli/linux.scrbl

@@ -1692,13 +1692,38 @@
   # 3. Format partition as ext4 (or ext2 or ext3):
   sudo mkfs.ext4 $diskPart -L <lbl-fsys-...> # -L <volume-label>
   #
-  # 4. verify:
+  # 4. verify with:
   lsblk --output \
           FSTYPE,PARTTYPE,PATH,MODEL,TRAN,LABEL,SIZE,PARTLABEL,MOUNTPOINTS \
         | sed 's/PARTLABEL/PARTLBL  /g' | sed 's/LABEL/FSLBL/g'
-  #
+  # 4. ... or verify also with:
   sudo parted $diskRoot print
+  # Model: VendorCo ProductCode (scsi)
+  # Disk /dev/sdd: 31.5GB
+  # Sector size (logical/physical): 512B/512B
+  # Partition Table: msdos
+  # Disk Flags:
+  #
+  # Number  Start   End     Size    Type     File system  Flags
+  # 2      1185MB  1188MB  2949kB  primary               esp
+  #
+  # 4. ... or verify also with:
   sudo fdisk --list $diskRoot
+  # Disk /dev/sdd: 29.3 GiB, 31457280000 bytes, 61440000 sectors
+  # Disk model: ProductCode
+  # Units: sectors of 1 * 512 = 512 bytes
+  # Sector size (logical/physical): 512 bytes / 512 bytes
+  # I/O size (minimum/optimal): 512 bytes / 512 bytes
+  # Disklabel type: dos
+  # Disk identifier: 0x00000000
+  #
+  # Device     Boot   Start     End Sectors  Size Id Type
+  # /dev/sdd1  *          0 2315063 2315064  1.1G  0 Empty
+  # /dev/sdd2       2315064 2320823    5760  2.8M ef EFI (FAT-12/16/32)
+  #
+  # 4. ... or verify also with:
+  sudo file --special-files $diskRoot
+  # /dev/sdd: ISO 9660 CD-ROM filesystem data (DOS/MBR boot sector) 'GUIX_X86_64-LINUX_1.5.0' (bootable)
   #
   # In the context of Linux tools like blkid and lsblk, it is not possible to
   # assign a custom label directly to the entire hard drive (as opposed to

notes/guix-guile-nix/guile.scrbl

@@ -52,8 +52,8 @@
   (iota 6)        ⇒ (0 1 2 3 4 5)
   (iota 4 2.5 -2) ⇒ (2.5 0.5 -1.5 -3.5)
 
-  (define my-list '(a b c d e))
-  (list-ref my-list 2)  ;; nth element of a list
+  (define my-list '(a0 b1 c2 d3 e4))
+  (list-ref my-list 2) ;; => c2 (nth element of a list)
 
   https://sourcegraph.com/search
   https://sourcehut.org
@@ -118,10 +118,16 @@
   (unspecified? *unspecified*)        ; => #t
   ;; The evaluated expression has no result specified:
   (equal? (when #f #t) *unspecified*) ; => #t
+  ;; However:
+  (equal? (when #f #t))               ; => #t
+  (equal? *unspecified*)              ; => #t
+  ;; *unspecified* is truthy. WTF!?!
+  (if (when #f #t) #t #f)  ; => #t
+  (if *unspecified* #t #f) ; => #t
   ;; *unspecified* is a value apart from both: empty list and boolean false
-  (eq? *unspecified* '()) ; => #f
-  (eq? *unspecified* #f)  ; => #f
-  (eq? *unspecified* #t)  ; => #f
+  (eq? *unspecified* '())  ; => #f
+  (eq? *unspecified* #f)   ; => #f
+  (eq? *unspecified* #t)   ; => #f
 
   Tail Call Optimisation
   the compiler will rewrite the recursive form into a serialised iterative form.
@@ -505,6 +511,7 @@
              (odd?  (lambda (n) (if (zero? n) #f (even? (- n 1))))))
       (even? 88))
 
+    (use-modules (srfi srfi-88)) ; provides keyword objects
     (keyword? #:foo)   ;; => #t
     ;; (keyword? :foo) ;; => error
     ;; (keyword? foo:) ;; => error
@@ -566,3 +573,16 @@
   Scheme[2][3] and are available in the GNU Guile implementation of that
   language.
 }
+
+@block{@block-name{Exactness}
+  ;; https://www.gnu.org/software/guile/docs/docs-2.0/guile-ref/Exactness.html
+  (exact? 2)           ; ⇒ #t
+  (exact? 0.5)         ; ⇒ #f
+  (exact? (/ 2))       ; ⇒ #t
+  (inexact->exact 0.5) ; ⇒ 1/2
+  ;; 12/10 is not exactly representable as a double (on most platforms).
+  ;; However, when reading a decimal number that has been marked exact with the
+  ;; "#e" prefix, Guile is able to represent it correctly.
+  (inexact->exact 1.2) ; ⇒ 5404319552844595/4503599627370496
+  #e1.2                ; ⇒ 6/5
+}