* Some utility functions for working with ATerms.

src/libnix/aterm.cc

@@ -0,0 +1,93 @@
+#include "aterm.hh"
+
+
+string atPrint(ATerm t)
+{
+    if (!t) throw Error("attempt to print null aterm");
+    char * s = ATwriteToString(t);
+    if (!s) throw Error("cannot print term");
+    return s;
+}
+
+
+ostream & operator << (ostream & stream, ATerm e)
+{
+    return stream << atPrint(e);
+}
+
+
+ATMatcher & atMatch(ATMatcher & pos, ATerm t)
+{
+    pos.t = t;
+    pos.pos = ATMatcher::funPos;
+    return pos;
+}
+
+
+static inline bool failed(const ATMatcher & pos)
+{
+    return pos.pos == ATMatcher::failPos;
+}
+
+
+static inline ATMatcher & fail(ATMatcher & pos)
+{
+    pos.pos = ATMatcher::failPos;
+    return pos;
+}
+
+
+ATMatcher & operator >> (ATMatcher & pos, ATerm & out)
+{
+    out = 0;
+    if (failed(pos)) return pos;
+    if (pos.pos == ATMatcher::funPos || 
+        ATgetType(pos.t) != AT_APPL ||
+        pos.pos >= (int) ATgetArity(ATgetAFun(pos.t)))
+        return fail(pos);
+    out = ATgetArgument(pos.t, pos.pos);
+    pos.pos++;
+    return pos;
+}
+
+
+ATMatcher & operator >> (ATMatcher & pos, string & out)
+{
+    out = "";
+    if (pos.pos == ATMatcher::funPos) {
+        if (ATgetType(pos.t) != AT_APPL) return fail(pos);
+        out = ATgetName(ATgetAFun(pos.t));
+        pos.pos = 0;
+    } else {
+        ATerm t;
+        pos = pos >> t;
+        if (failed(pos)) return pos;
+        if (ATgetType(t) != AT_APPL ||
+            ATgetArity(ATgetAFun(t)) != 0)
+            return fail(pos);
+        out = ATgetName(ATgetAFun(t));
+    }
+    return pos;
+}
+
+
+ATMatcher & operator >> (ATMatcher & pos, const string & s)
+{
+    string s2;
+    pos = pos >> s2;
+    if (failed(pos)) return pos;
+    if (s != s2) return fail(pos);
+    return pos;
+}
+
+
+ATMatcher & operator >> (ATMatcher & pos, ATermList & out)
+{
+    out = 0;
+    ATerm t;
+    pos = pos >> t;
+    if (failed(pos)) return pos;
+    if (ATgetType(t) != AT_LIST) return fail(pos);
+    out = (ATermList) t;
+    return pos;
+}