boot2

Playing with the boostrap
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088-pmatch-literals.scm (1361B)

      1 ; pmatch — literal-shaped patterns: string, char, bool, sym, ().
      2 
      3 ;; String pattern: byte-for-byte equality.
      4 (if (= 1
      5        (pmatch "hi"
      6          ("ho" (sys-exit 90))
      7          ("hi" 1)
      8          (else (sys-exit 91))))
      9     0 (sys-exit 1))
     10 
     11 ;; Character literals are integers; #\A == 65.
     12 (if (= 65
     13        (pmatch #\A
     14          (#\B (sys-exit 92))
     15          (#\A 65)
     16          (else (sys-exit 93))))
     17     0 (sys-exit 2))
     18 
     19 ;; #t / #f match by eq?.
     20 (if (= 11
     21        (pmatch #t
     22          (#f (sys-exit 94))
     23          (#t 11)))
     24     0 (sys-exit 3))
     25 
     26 ;; Bare symbol pattern matches that exact symbol; ,x in a sibling
     27 ;; clause is the binder spelling.
     28 (if (eq? 'matched
     29          (pmatch 'foo
     30            (bar  'no-bar)
     31            (foo  'matched)
     32            (,x   'fallback)))
     33     0 (sys-exit 4))
     34 
     35 ;; Symbol-vs-binder: ,x binds anything; the literal symbol clause
     36 ;; for `foo` only fires on exactly `foo`.
     37 (if (eq? 'bound-baz
     38          (pmatch 'baz
     39            (foo 'literal-foo)
     40            (,x  (if (eq? x 'baz) 'bound-baz 'unexpected))))
     41     0 (sys-exit 5))
     42 
     43 ;; () pattern matches the empty list and nothing else.
     44 (if (= 22
     45        (pmatch '()
     46          ((,h . ,t) (sys-exit 95))
     47          (() 22)))
     48     0 (sys-exit 6))
     49 
     50 ;; () pattern doesn't match a non-empty list.
     51 (if (= 33
     52        (pmatch '(a)
     53          (() (sys-exit 96))
     54          ((,_) 33)))
     55     0 (sys-exit 7))
     56 
     57 (sys-exit 0)