54 lines
2.6 KiB
Plaintext
54 lines
2.6 KiB
Plaintext
vocabulary V {
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type index isa int
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queen(index, index)
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n : index
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type diag isa int
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diag1(index, index) : diag
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diag2(index, index) : diag
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type dist isa int
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k: dist
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}
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structure S : V {
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index = {1..20}
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diag = {1..39}
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n = 20
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k = 5
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}
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theory T : V {
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{ diag1(x, y) = x - y + n. }
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{ diag2(x, y) = x + y - 1. }
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!x : ?=1y : queen(x, y). //(1)
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!y : ?=1x : queen(x, y). //(2)
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!d : #{x y : queen(x, y) & diag1(x, y) = d} < 2. //(3)
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!d : #{x y : queen(x, y) & diag2(x, y) = d} < 2. //(4)
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!x1 y1 x2 y2: queen(x1, y1) & queen(x2, y2) & x1 ~= x2 => abs(x1-x2) + abs(y1-y2) >= k.
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//~? x1 y1 x2 y2: queen(x1, y1) & queen(x2, y2) & ~x1 = x2 & abs(x1-x2) + abs(y1-y2) =< k.
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}
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procedure main() {
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/* Important: the option xsb is not present in every installation, in order to obtain
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* efficient definition evaluation with XSB, you should compile IDP yourself
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* (as XSB cannot be distributed with dynamically linked binaries
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*/
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stdoptions.xsb=true // use XSB to calculate definitions that can be
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// calculated in advance
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diags = calculatedefinitions(T,S) // calculate the definitions for symbols diag1 and diag2
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// The resulting variable (diags) contains a single structure
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// in which the defined symbols are two-valued
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print("Definitions calculated:\n"..tostring(diags))
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stdoptions.nbmodels=0 // search for all models
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solutions = modelexpand(T,diags) // solutions is now a (Lua) table with all models
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// Note that instead of diags, we could also do modelexpand on S,
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// since the standard modelexpand workflow contains a call to
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// calculatedefinitions
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print(#solutions.." models found") // "#" retrieves table size, .. is the lua concatenation
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for i,sol in ipairs(solutions) do // A for-loop to iterate over all solutions.
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print("model "..i..":") // ipairs is a builtin Lua procedure which allows you
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// to loop over the index and table elements of a table
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print(sol)
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end
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}
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