improve AST to string conversion

Since there is no direct AST representation for terms of form `f(a;b)`, they are represented as `f(a);f(b)`. This commit changes printing, so that such pools are printed in the shorter form. This way, the string representation of rules containing pools in arguments of predicates is parsable. Addresses #171.
potassco · Dec 8, 2019 · 9a51241 · 9a51241
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diff --git a/app/clingo/tests/python/ast2.lp b/app/clingo/tests/python/ast2.lp
@@ -97,8 +97,10 @@ def trm():
         ("p((a^b)).", ["p((a^b))."]),
         ("p(a..b).", ["p((a..b))."]),
         ("p((),(1,),f(),f(1,2)).", ["p((),(1,),f,f(1,2))."]),
-        ("p(a;b).", ["(p(a);p(b))."]),
+        ("p(a;b).", ["p(a;b)."]),
+        ("p(@f(a;b)).", ["p(@f(a;b))."]),
         ("p((a,;b)).", ["p(((a,);b))."]),
+        ("p(((a,);b)).", ["p(((a,);b))."]),
         ("1 $+ 3 $* $x $+ 7 $< 2 $< 3.", ["1$+3$*$x$+7$<2$<3."]),
     ])
 

diff --git a/app/clingo/tests/python/ast2.sol b/app/clingo/tests/python/ast2.sol
@@ -1,3 +1,3 @@
 Step: 1
-bdl(0,ok) bdl(1,ok) bdl(2,ok) bdl(3,ok) bdl(4,ok) bdl(5,ok) bdl(6,ok) bdl(7,ok) bdl(8,ok) bdl(9,ok) hdl(0,ok) hdl(1,ok) hdl(2,ok) hdl(3,ok) hdl(4,ok) hdl(5,ok) hdl(6,ok) hdl(7,ok) lit(0,ok) lit(1,ok) lit(2,ok) lit(3,ok) lit(4,ok) lit(5,ok) lit(6,ok) lit(7,ok) stm(0,ok) stm(1,ok) stm(10,ok) stm(11,ok) stm(12,ok) stm(13,ok) stm(14,ok) stm(15,ok) stm(16,ok) stm(17,ok) stm(18,ok) stm(2,ok) stm(3,ok) stm(4,ok) stm(5,ok) stm(6,ok) stm(7,ok) stm(8,ok) stm(9,ok) thd(0,ok) thd(1,ok) thd(2,ok) tht(0,ok) tht(1,ok) tht(10,ok) tht(11,ok) tht(2,ok) tht(3,ok) tht(4,ok) tht(5,ok) tht(6,ok) tht(7,ok) tht(8,ok) tht(9,ok) trm(0,ok) trm(1,ok) trm(10,ok) trm(11,ok) trm(12,ok) trm(13,ok) trm(14,ok) trm(15,ok) trm(16,ok) trm(2,ok) trm(3,ok) trm(4,ok) trm(5,ok) trm(6,ok) trm(7,ok) trm(8,ok) trm(9,ok)
+bdl(0,ok) bdl(1,ok) bdl(2,ok) bdl(3,ok) bdl(4,ok) bdl(5,ok) bdl(6,ok) bdl(7,ok) bdl(8,ok) bdl(9,ok) hdl(0,ok) hdl(1,ok) hdl(2,ok) hdl(3,ok) hdl(4,ok) hdl(5,ok) hdl(6,ok) hdl(7,ok) lit(0,ok) lit(1,ok) lit(2,ok) lit(3,ok) lit(4,ok) lit(5,ok) lit(6,ok) lit(7,ok) stm(0,ok) stm(1,ok) stm(10,ok) stm(11,ok) stm(12,ok) stm(13,ok) stm(14,ok) stm(15,ok) stm(16,ok) stm(17,ok) stm(18,ok) stm(2,ok) stm(3,ok) stm(4,ok) stm(5,ok) stm(6,ok) stm(7,ok) stm(8,ok) stm(9,ok) thd(0,ok) thd(1,ok) thd(2,ok) tht(0,ok) tht(1,ok) tht(10,ok) tht(11,ok) tht(2,ok) tht(3,ok) tht(4,ok) tht(5,ok) tht(6,ok) tht(7,ok) tht(8,ok) tht(9,ok) trm(0,ok) trm(1,ok) trm(10,ok) trm(11,ok) trm(12,ok) trm(13,ok) trm(14,ok) trm(15,ok) trm(16,ok) trm(17,ok) trm(18,ok) trm(2,ok) trm(3,ok) trm(4,ok) trm(5,ok) trm(6,ok) trm(7,ok) trm(8,ok) trm(9,ok)
 SAT
diff --git a/libclingo/clingo.hh b/libclingo/clingo.hh
@@ -5058,8 +5058,42 @@ inline std::ostream &operator<<(std::ostream &out, CSPProduct const &x) {
 
 inline std::ostream &operator<<(std::ostream &out, Pool const &x) {
     // NOTE: there is no representation for an empty pool
-    if (x.arguments.empty()) { out << "(1/0)"; }
-    else                     { out << Detail::print(x.arguments, "(", ";", ")", true); }
+    auto &args = x.arguments;
+    if (args.empty()) { out << "(1/0)"; }
+    if (args.size() == 1) { out << args[0]; }
+    else {
+        bool equal{true};
+        Function const *old{nullptr};
+        for (auto &arg : args) {
+            if (arg.data.is<Function>()) {
+                auto &fun = arg.data.get<Function>();
+                if (!old) { old = &fun; }
+                else if (strcmp(fun.name, old->name) != 0 || fun.external != old->external) {
+                    equal = false;
+                    break;
+                }
+            }
+            else {
+                equal = false;
+                break;
+            }
+        }
+        if (equal) {
+            out << (old->external ? "@" : "") << old->name << "(";
+            bool sem = false;
+            for (auto &arg : args) {
+                if (sem) { out << ";"; }
+                else { sem = true; }
+                auto &pargs = arg.data.get<Function>().arguments;
+                bool tc = old->name[0] == '\0' && pargs.size() == 1;
+                out << Detail::print(pargs, "", ",", tc ? "," : "", true);
+            }
+            out << ")";
+        }
+        else {
+            out << Detail::print(x.arguments, "(", ";", ")", true);
+        }
+    }
     return out;
 }
 

diff --git a/libclingo/tests/ast.cc b/libclingo/tests/ast.cc
@@ -165,8 +165,10 @@ TEST_CASE("parse-ast", "[clingo]") {
         REQUIRE(parse("p((a^b)).") == "p((a^b)).");
         REQUIRE(parse("p(a..b).") == "p((a..b)).");
         REQUIRE(parse("p((),(1,),f(),f(1,2)).") == "p((),(1,),f,f(1,2)).");
-        REQUIRE(parse("p(a;b).") == "(p(a);p(b)).");
+        REQUIRE(parse("p(@f(a;b)).") == "p(@f(a;b)).");
+        REQUIRE(parse("p(a;b).") == "p(a;b).");
         REQUIRE(parse("p((a,;b)).") == "p(((a,);b)).");
+        REQUIRE(parse("p(((a,);b)).") == "p(((a,);b)).");
         REQUIRE(parse("1 $+ 3 $* $x $+ 7 $< 2 $< 3.") == "1$+3$*$x$+7$<2$<3.");
     }
     SECTION("theory terms") {

diff --git a/libpyclingo/pyclingo.cc b/libpyclingo/pyclingo.cc
@@ -5372,7 +5372,44 @@ given in the [grammar](.) above.
             case ASTType::Pool: {
                 Object args = fields_.getItem("arguments");
                 if (args.empty()) { out << "(1/0)"; }
-                else              { out << printList(args, "(", ";", ")", true); }
+                if (args.size() == 1) { out << args.getItem(0); }
+                else {
+                    bool equal = true, old_ext = false;
+                    Object old_name;
+                    for (auto arg : args.iter()) {
+                        if (arg.getAttr("type") == ASTType::getAttr(ASTType::Function)) {
+                            auto name = arg.getAttr("name");
+                            auto ext = pyToCpp<bool>(arg.getAttr("external"));
+                            if (!old_name.valid()) {
+                                old_name = name;
+                                old_ext = ext;
+                            }
+                            else if (name != old_name || ext != old_ext) {
+                                equal = false;
+                                break;
+                            }
+                        }
+                        else {
+                            equal = false;
+                            break;
+                        }
+                    }
+                    if (equal) {
+                        out << (old_ext ? "@" : "") << old_name << "(";
+                        bool sem = false;
+                        for (auto arg : args.iter()) {
+                            if (sem) { out << ";"; }
+                            else { sem = true; }
+                            auto pargs = arg.getAttr("arguments");
+                            bool tc = old_name.size() == 0 && pargs.size() == 1;
+                            out << printList(pargs, "", ",", tc ? "," : "", true);
+                        }
+                        out << ")";
+                    }
+                    else {
+                        out << printList(args, "(", ";", ")", true);
+                    }
+                }
                 break;
             }
             case ASTType::CSPProduct: {