40 lines
1.2 KiB
Scheme
40 lines
1.2 KiB
Scheme
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;;;;;; Riatables: alternative hash tables -*- Scheme -*-
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;;;;;; Miscellaneous support utilities
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;;; Taylor Campbell wrote this code; he places it in the public domain.
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(define (gc-stamp)
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(memory-status (enum memory-status-option gc-count) 0))
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(define (descriptor-hash object)
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(memory-status (enum memory-status-option pointer-hash) object))
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(define (modular-descriptor-hash object mod)
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(modulo (descriptor-hash object) mod))
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;;; Silly string hashers. I use Scheme48's STRING-HASH, not a better
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;;; algorithm (Scheme48's is pretty terrible), because it's a primitive
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;;; in the VM and therefore faster than anything in plain Scheme.
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(define (modular-string-hash string mod)
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(modulo (string-hash string) mod))
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(define (string-ci-hash string)
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(let* ((length (string-length string))
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(new-string (make-string length)))
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(do ((i 0 (+ i 1)))
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((= i length))
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(string-set! new-string i (char-downcase (string-ref string i))))
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(string-hash string)))
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(define (modular-string-ci-hash string mod)
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(modulo (string-ci-hash string) mod))
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(define (integer-hash integer) (abs integer))
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(define (modular-integer-hash integer mod)
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(modulo integer mod))
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(define (exact-integer? x)
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(and (integer? x) (exact? x)))
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