Contrib packages

Trivia has several contrib packages that integrates to other libraries.

trivia.ppcre

Provides 3 patterns: ppcre, split and split*.

ppcre pattern

ppcre pattern is a wrapper around ppcre:scan-to-strings.

Syntax

ppcre (regexp &key start end sharedp) &rest subpatterns (long form)

ppcre regexp &rest subpatterns (short form)

(match "abcccdddcd"
  ((ppcre "ab([cd]+)" var)
    var))
;; -> "cccdddcd"

split, split* pattern

split pattern is a wrapper around ppcre:split. split* pattern is a soft-match variant.

Syntax

split regexp &rest subpatterns

split* regexp &rest subpatterns

(match "a b"
  ((split " " var)
    :does-not-match)
  ((split " " var var2 var3)
    :does-not-match)
  ((split " " var var2)
    (list var var2)))
;; -> ("a" "b")

(match "a b"
  ((split* " " var)
    var)
;; -> ("a")

trivia.cffi

-> pattern provides a foreign slot access.

Syntax

-> foreign-struct-type &rest slots

• slots := {slot}*
• slot := slotname | (& slotname) | (slotname subpattern)
• slotname := symbol

Example:

(defcstruct bar
  (baz :int))
(defcstruct foo
  (bar (:struct bar)))

(match (foreign-alloc 'foo) ; returns a pointer
  ((-> (:struct foo)
     bar                            ; foreign-slot-value access (leaf pattern)
     (& bar)                        ; explicit foreign-slot-pointer access
     (bar bar)                      ; implicit foreign-slot-pointer access (nested pattern)
     (bar                           ; implicit foreign-slot-pointer access (nested pattern)
      (-> (:struct bar)
        baz)))                      ; leaf node: value access
   baz)) ;; uninitialized value

Note: Above example does not actually compile because it reuses the same variable.

trivia.quasiquote

Loading this package and using the :fare-quasiquote readtable, you can now write a pattern with a quasiquoted list.

(in-readtable :fare-quasiquote)
;; or better,
(ql:quickload :cl-syntax-quasiquote)
(cl-syntax:use-syntax :fare-quasiquote)

(match (list 1 2)
  (`(,b ,c)
    (assert (= 1 b))
    (assert (= 2 c))))