;;; Logic problem inference system

;; Establish categories

to category :category.name :members
print (list "category :category.name :members)
if not namep "categories [make "categories []]
make "categories lput :category.name :categories
make :category.name :members
foreach :members [pprop ? "category :category.name]
end

;; Verify and falsify matches

to verify :a :b
settruth :a :b "true
end

to falsify :a :b
settruth :a :b "false
end

to settruth :a :b :truth.value
if equalp (gprop :a "category) (gprop :b "category) [stop]
localmake "oldvalue get :a :b
if equalp :oldvalue :truth.value [stop]
if equalp :oldvalue (not :truth.value) ~
   [(throw "error (sentence [inconsistency in settruth]
                            :a :b :truth.value))]
print (list :a :b "-> :truth.value)
store :a :b :truth.value
settruth1 :a :b :truth.value
settruth1 :b :a :truth.value
if not emptyp :oldvalue ~
   [foreach (filter [equalp first ? :truth.value] :oldvalue)
            [apply "settruth butfirst ?]]
end

to settruth1 :a :b :truth.value
apply (word "find not :truth.value) (list :a :b)
foreach (gprop :a "true) [settruth ? :b :truth.value]
if :truth.value [foreach (gprop :a "false) [falsify ? :b]
                 pprop :a (gprop :b "category) :b]
pprop :a :truth.value (fput :b gprop :a :truth.value)
end

to findfalse :a :b
foreach (filter [not equalp get ? :b "true] peers :a) ~
        [falsify ? :b]
end

to findtrue :a :b
if equalp (count peers :a) (1+falses :a :b) ~
   [verify (find [not equalp get ? :b "false] peers :a)
           :b]
end

to falses :a :b
output count filter [equalp "false get ? :b] peers :a
end

to peers :a
output thing gprop :a "category
end

;; Common types of clues

to differ :list
print (list "differ :list)
foreach :list [differ1 ? ?rest]
end

to differ1 :a :them
foreach :them [falsify :a ?]
end

to justbefore :this :that :lineup
falsify :this :that
falsify :this last :lineup
falsify :that first :lineup
justbefore1 :this :that :lineup
end

to justbefore1 :this :that :slotlist
if emptyp butfirst :slotlist [stop]
equiv :this (first :slotlist) :that (first butfirst :slotlist)
justbefore1 :this :that (butfirst :slotlist)
end

;; Remember conditional linkages

to implies :who1 :what1 :truth1 :who2 :what2 :truth2
implies1 :who1 :what1 :truth1 :who2 :what2 :truth2
implies1 :who2 :what2 (not :truth2) :who1 :what1 (not :truth1)
end

to implies1 :who1 :what1 :truth1 :who2 :what2 :truth2
localmake "old1 get :who1 :what1
if equalp :old1 :truth1 [settruth :who2 :what2 :truth2  stop]
if equalp :old1 (not :truth1) [stop]
if memberp (list :truth1 :who2 :what2 (not :truth2)) :old1 ~
   [settruth :who1 :what1 (not :truth1)  stop]
if memberp (list :truth1 :what2 :who2 (not :truth2)) :old1 ~
   [settruth :who1 :what1 (not :truth1)  stop]
store :who1 :what1 ~
      fput (list :truth1 :who2 :what2 :truth2) :old1
end

to equiv :who1 :what1 :who2 :what2
implies :who1 :what1 "true :who2 :what2 "true
implies :who2 :what2 "true :who1 :what1 "true
end

to xor :who1 :what1 :who2 :what2
implies :who1 :what1 "true :who2 :what2 "false
implies :who1 :what1 "false :who2 :what2 "true
end

;; Interface to property list mechanism

to get :a :b
output gprop :a :b
end

to store :a :b :val
pprop :a :b :val
pprop :b :a :val
end

;; Print the solution

to solution
foreach thing first :categories [solve1 ? butfirst :categories]
end

to solve1 :who :order
type :who
foreach :order [type "| |   type gprop :who ?]
print []
end

;; Get rid of old problem data

to cleanup
if not namep "categories [stop]
ern :categories
ern "categories
erpls
end

;; Anita Harnadek's problem

to cub.reporter
cleanup
category "first [Jane Larry Opal Perry]
category "last [Irving King Mendle Nathan]
category "age [32 38 45 55]
category "job [drafter pilot sergeant driver]
differ [Jane King Larry Nathan]
says "Jane "Irving 45
says "King "Perry "driver
says "Larry "sergeant 45
says "Nathan "drafter 38
differ [Mendle Jane Opal Nathan]
says "Mendle "pilot "Larry
says "Jane "pilot 45
says "Opal 55 "driver
says "Nathan 38 "driver
print []
solution
end

to says :who :what1 :what2
print (list "says :who :what1 :what2)
xor :who :what1 :who :what2
end

;; Diane Baldwin's problem

to foote.family
cleanup
category "when [1st 2nd 3rd 4th 5th]
category "name [Felix Fred Frank Francine Flo]
category "street [Field Flag Fig Fork Frond]
category "item [food film flashlight fan fiddle]
category "position [1 2 3 4 5]
print [Clue 1]
justbefore "Flag "2nd :position
justbefore "2nd "Fred :position
print [Clue 2]
male [film Fig 5th]
print [Clue 3]
justbefore "flashlight "Fork :position
justbefore "Fork "1st :position
female [1st]
print [Clue 4]
falsify "5th "Frond
falsify "5th "fan
print [Clue 5]
justbefore "Francine "Frank :position
justbefore "Francine "Frank :when
print [Clue 6]
female [3rd Flag]
print [Clue 7]
justbefore "fiddle "Frond :when
justbefore "Flo "fiddle :when
print []
solution
end

to male :stuff
differ sentence :stuff [Francine Flo]
end

to female :stuff
differ sentence :stuff [Felix Fred Frank]
end

;;; Combinatorics toolkit

to combs :list :howmany
if equalp :howmany 0 [output [[]]]
if equalp :howmany count :list [output (list :list)]
output sentence (map [fput first :list ?]
                     combs (butfirst :list) (:howmany-1)) ~
      (combs (butfirst :list) :howmany)
end

to fact :n
output cascade :n [# * ?] 1
end

to perms :n :r
if equalp :r 0 [output 1]
output :n * perms :n-1 :r-1
end

to choose :n :r
output (perms :n :r)/(fact :r)
end

;; The socks problem

to socks :list
localmake "total combs (expand :list) 2
localmake "matching filter [equalp first ? last ?] :total
print (sentence [there are] count :total [possible pairs of socks.])
print (sentence [of these,] count :matching [are matching pairs.])
print sentence [probability of match =] ~
      word (100 * (count :matching)/(count :total)) "%
end

to expand :list
if emptyp :list [output []]
if numberp first :list ~
   [output cascade (first :list)
                   [fput first butfirst :list ?]
                   (expand butfirst butfirst :list)]
output fput first :list expand butfirst :list
end

to socktest
localmake "first pick [brown brown brown brown brown brown 
                       blue blue blue blue]
localmake "second ~
          pick (ifelse equalp :first "brown ~
                       [[brown brown brown brown brown
                         blue blue blue blue]] ~
                       [[brown brown brown brown brown brown
                         blue blue blue]])
output equalp :first :second
end

;; The Simplex lock problem

to lock :buttons
output cascade :buttons [? + lock1 :buttons #] 1
end

to lock1 :total :buttons
localmake "perms perms :total :buttons
output cascade (twoto (:buttons-1)) [? + lock2 :perms #-1 1] 0
end

to lock2 :perms :links :factor
if equalp :links 0 [output :perms/(fact :factor)]
if equalp (remainder :links 2) 0 ~
   [output lock2 :perms/(fact :factor) :links/2 1]
output lock2 :perms (:links-1)/2 :factor+1
end

to twoto :power
output cascade :power [2 * ?] 1
end

to simplex :buttons
output 2 * f :buttons
end

to f :n
if equalp :n 0 [output 1]
output cascade :n [? + ((choose :n (#-1)) * f (#-1))] 0
end

to simp :n
output round (fact :n)/(power (ln 2) (:n+1))
end

;; The multinomial expansion problem

to t :n :k
if equalp :k 0 [output 1]
if equalp :n 0 [output 0]
output (t :n :k-1)+(t :n-1 :k)
end