131 lines
3.5 KiB
Factor
131 lines
3.5 KiB
Factor
! Copyright (C) 2018 Alexander Ilin.
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! See http://factorcode.org/license.txt for BSD license.
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USING: arrays help.markup help.syntax kernel quotations sequences ;
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IN: boolean-expr
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ABOUT: "boolean-expr"
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ARTICLE: "boolean-expr" "Boolean expressions"
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"The " { $vocab-link "boolean-expr" } " vocab demonstrates the use of Unicode symbols in source files and multi-method dispatch."
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;
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HELP: cnf
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{ $values
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{ "expr" □ }
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{ "cnf" array }
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}
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{ $description "Convert the " { $snippet "expr" } " to Conjuctive Normal Form (CNF), i.e. an array of subexpressions, each not containing conjunctions. See " { $url "https://en.wikipedia.org/wiki/Conjunctive_normal_form" } "." }
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{ $examples
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{ $example "USING: boolean-expr prettyprint ;"
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"X Y Z ⋀ ⋀ cnf ."
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"{ { X Y Z } }"
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}
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{ $example "USING: boolean-expr prettyprint ;"
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"X Y Z ⋁ ⋁ cnf ."
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"{ { X } { Y } { Z } }"
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}
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}
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{ $notes "Actually, looking at the exapmles above, to me it seems more like the Disjunctive Normal Form (DNF). Maybe the implementation needs to be fixed."
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} ;
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HELP: expr.
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{ $values
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{ "expr" □ }
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}
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{ $description "Print the expression followed by newline." }
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{ $examples
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{ $example "USING: boolean-expr ;"
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"X Y ⋁ X ¬ Y ⋀ ⋀ op."
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"((X ⋀ (¬X ⋀ Y)) ⋁ (Y ⋀ (¬X ⋀ Y)))"
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}
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} ;
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HELP: op.
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{ $values
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{ "expr" □ }
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}
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{ $description "Print the expression." }
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{ $examples
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{ $example "USING: boolean-expr ;"
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"X Y ⋁ X ¬ Y ⋀ ⋀ op."
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"((X ⋀ (¬X ⋀ Y)) ⋁ (Y ⋀ (¬X ⋀ Y)))"
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}
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} ;
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{ expr. op. } related-words
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HELP: satisfiable?
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{ $values
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{ "expr" □ }
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{ "?" boolean }
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}
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{ $description "Return " { $link t } " if the " { $snippet "expr" } " can be true." }
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{ $examples
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{ $example "USING: boolean-expr prettyprint ;"
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"⊤ satisfiable? ."
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"t"
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}
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{ $example "USING: boolean-expr prettyprint ;"
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"⊥ satisfiable? ."
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"f"
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}
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{ $example "USING: boolean-expr prettyprint ;"
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"X X ¬ ⋀ satisfiable? ."
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"f"
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}
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{ $example "USING: boolean-expr prettyprint ;"
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"X Y ⋁ X ¬ Y ¬ ⋀ ⋀ satisfiable? ."
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"f"
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}
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{ $example "USING: boolean-expr prettyprint ;"
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"X Y ⋁ X ¬ Y ⋀ ⋀ satisfiable? ."
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"t"
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}
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} ;
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HELP: ¬
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{ $class-description "Logical negation (NOT)." $nl
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{ $snippet "¬(¬A) " { $link ≣ } " A" } "."
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} ;
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HELP: →
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{ $values
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{ "x" □ } { "y" □ }
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{ "expr" □ }
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}
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{ $description "Material implication (if..then)." $nl
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{ $snippet "x→y" } " " { $link ≣ } " " { $link ¬ } "x" { $link ⋁ } "y"
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} ;
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HELP: ≣
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{ $values
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{ "x" □ } { "y" □ }
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{ "expr" □ }
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}
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{ $description "Material equivalence (if and only if)." $nl
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{ $snippet "(x≣y) ≣ ((x" } { $link ⋀ } { $snippet "y) " }
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{ $link ⋁ } { $snippet " (" } { $link ¬ } { $snippet "x" } { $link ⋀ } { $link ¬ } { $snippet "y))" }
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} ;
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HELP: ⊕
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{ $values
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{ "x" □ } { "y" □ }
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{ "expr" □ }
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}
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{ $description "Exclusive disjunction (XOR)." } ;
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HELP: ⊤
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{ $class-description "Logical tautology. This statement is unconditionally true." } ;
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HELP: ⊥
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{ $class-description "Logical contradiction. This statement is unconditionally false." } ;
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HELP: ⋀
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{ $class-description "Logical conjuction (AND)." } ;
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HELP: ⋁
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{ $class-description "Logical disjunction (OR)." } ;
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HELP: □
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{ $class-description "A union class of all classes defined in this vocab. In methods signatures it stands for \"any variable or expression\"." } ;
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