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annotate 3-Prolog/day2-maths.pl @ 67:8906b5a4517f

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Calculate and validate boxes The solver now creates answers for valid sudoku, but doesn't reject invalid ones (e.g. dupe in column)
author IBBoard <dev@ibboard.co.uk>
date Sat, 07 Oct 2017 15:07:34 +0100
parents f86bb0d669be
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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59
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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1 % First use of variable assignment!
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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2 % We use a mix of rules and facts to do maths on lists.
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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3 count(0, []).
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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4 % This seems backwards, but we're saying "Count of a list with a head and a tail
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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5 % is the count of its tail (which will be assigned to TailCount) plus one, which
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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6 % is then assigned to Count, which gets passed back out"
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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7 count(Count, [Head|Tail]) :- count(TailCount, Tail), Count is TailCount + 1.
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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8
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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9 sum(0, []).
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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10 sum(Total, [Head|Tail]) :- count(Sum, Tail), Total is Head + Sum.
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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11
f86bb0d669be Add a quick bit of maths code (list counting/summing)
IBBoard <dev@ibboard.co.uk>
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12 average(Average, List) :- sum(Sum, List), count(Count, List), Average is Sum / Count.