Hi Guile Users!
I've noticed a strange behavior of hash tables. I put in symbols as keys
and integers as values, but when I try to get the integers out again by
using the same symbol, I get back a #f instead. Here is the code I am using:
~~~~~~~~
(use-modules
;; SRFI 60: procedures for treating integers as bits
(srfi srfi-60)
(ice-9 hash-table))
(define SQUARES
;; vector, constant time access
#('A1 'B1 'C1 'D1 'E1 'F1 'G1 'H1
'A2 'B2 'C2 'D2 'E2 'F2 'G2 'H2
'A3 'B3 'C3 'D3 'E3 'F3 'G3 'H3
'A4 'B4 'C4 'D4 'E4 'F4 'G4 'H4
'A5 'B5 'C5 'D5 'E5 'F5 'G5 'H5
'A6 'B6 'C6 'D6 'E6 'F6 'G6 'H6
'A7 'B7 'C7 'D7 'E7 'F7 'G7 'H7
'A8 'B8 'C8 'D8 'E8 'F8 'G8 'H8))
(define square-pos->bit-integer
(lambda (pos)
(expt 2 pos)))
(define make-squares-to-integer-mapping
(lambda (squares)
(let* ([num-squares (vector-length squares)]
[lookup-table (make-hash-table num-squares)])
(let loop ([square-pos 0])
(cond
[(< square-pos num-squares)
#;(display
(simple-format
#f "setting at key: ~a\n" (vector-ref squares square-pos)))
(hash-set! lookup-table
(vector-ref squares square-pos)
(square-pos->bit-integer square-pos))
(loop (+ square-pos 1))]
[else lookup-table])))))
(define SQUARES-TO-INTEGERS
(make-squares-to-integer-mapping SQUARES))
(hash-ref SQUARES-TO-INTEGERS 'A1)
~~~~~~~~
Surprisingly, I cannot get out any value of the ones stored in the hash
table. But when I use:
(hash-map->list cons SQUARES-TO-INTEGERS)
I can clearly see, that under the keys I have in SQUARES, are the
numbers stored in the hash table.
Also I use hash-ref, which is supposed to compare using equal?, which
for symbols like 'A1 and 'A1 returns #t, so I think my lookup should work.
Why can I not get the integers out of the hash table?
Regards,
Zelphir
