Mercurial > repos > other > SevenLanguagesInSevenWeeks

comparison 3-Prolog/readme.txt @ 58:90c4b7f28690

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Add initial Day 2 notes for Prolog
author IBBoard <dev@ibboard.co.uk>
date Tue, 26 Sep 2017 20:58:49 +0100
parents 005ae3fad18f
children 05871e7ac124
comparison
equal deleted inserted replaced
57:c9873b78e8c2 58:90c4b7f28690
10 10
11 When you ask a question with a placeholder, the placeholder has to be capitalised. Lower-case makes it an atom. 11 When you ask a question with a placeholder, the placeholder has to be capitalised. Lower-case makes it an atom.
12 When Prolog returns its answers, type ";" to get the next response or "a" to get all. Sometimes Prolog will end multiple responses 12 When Prolog returns its answers, type ";" to get the next response or "a" to get all. Sometimes Prolog will end multiple responses
13 with "no", sometimes with "yes". This depends on whether it needs to do more calculations to check for more answers ("no") 13 with "no", sometimes with "yes". This depends on whether it needs to do more calculations to check for more answers ("no")
14 or whether it knows it successfully gave you everything ("yes"). 14 or whether it knows it successfully gave you everything ("yes").
15
16 Rules don't need to be defined once. If you define the following:
17
18 ancestor(X, Y) :- father(X, Y).
19 ancestor(X, Y) :- father(X, Z), ancestor(Z, Y).
20
21 then Prolog will check both "definitions" of the rule.
22
23 (Note: putting the recursive "ancestor/2" call at the end is called "tail recursion" and the language can optimise it to
24 reduce call stack exhaustion issues)