23 lines
958 B
Plaintext
23 lines
958 B
Plaintext
;; Page 12 of the manual; this does NOT do what I expect a modern
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;; ASSOC to do!
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;; Modern ASSOC would be:
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;; assoc[x; l] = [null[l] -> NIL;
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;; and[consp[car[l]]; eq[caar[l]; x]] -> cdar[l];
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;; T -> assoc[x; cdr[l]]]
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;; In the Lisp 1.5 statement of ASSOC, there's no account of what should happen
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;; if the key (here `x`) is not present on the association list `a`. It seems
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;; inevitable that this causes an infinite run up the stack until it fails with
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;; stack exhaustion. Consequently this may be right but I'm not implementing it!
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;; assoc[x; a] = [equal[caar[a]; x] -> car[a];
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;; T -> assoc[x; cdr[a]]]
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;; Consequently, my solution is a hybrid. It returns the pair from the
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;; association list, as the original does, but it traps the end of list
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;; condition, as a modern solution would.
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assoc[x; l] = [null[l] -> NIL;
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and[consp[car[l]]; eq[caar[l]; x]] -> car[l];
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T -> assoc[x; cdr[l]]]
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