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changeset 59:f86bb0d669be

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Add a quick bit of maths code (list counting/summing)
author IBBoard <dev@ibboard.co.uk>
date Wed, 27 Sep 2017 20:19:01 +0100
parents 90c4b7f28690
children 643eec1f9e3a
files 3-Prolog/day2-maths.pl
diffstat 1 files changed, 12 insertions(+), 0 deletions(-) [+]
line wrap: on
line diff
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/3-Prolog/day2-maths.pl	Wed Sep 27 20:19:01 2017 +0100
@@ -0,0 +1,12 @@
+% First use of variable assignment!
+% We use a mix of rules and facts to do maths on lists.
+count(0, []).
+% This seems backwards, but we're saying "Count of a list with a head and a tail
+% is the count of its tail (which will be assigned to TailCount) plus one, which
+% is then assigned to Count, which gets passed back out"
+count(Count, [Head|Tail]) :- count(TailCount, Tail), Count is TailCount + 1.
+
+sum(0, []).
+sum(Total, [Head|Tail]) :- count(Sum, Tail), Total is Head + Sum.
+
+average(Average, List) :- sum(Sum, List), count(Count, List), Average is Sum / Count.
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