JSON access in Rascal (even better than in SLPS)

rascal/src/TwiSKO.rsc

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+@contributor{Vadim Zaytsev - vadim@grammarware.net - SWAT, CWI}
+module TwiSKO
+// TWItter to subatomic Scientific Knowledge Objects
+
+import io::json::Parser;
+import io::json::Access;
+
+public void go()
+{
+	list[JSO] tweets = gimmeArray(loc2jso(|home:///workspace/open/data/last1000.json|));
+}

rascal/src/io/json/ADT.rsc

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+@contributor{Vadim Zaytsev - vadim@grammarware.net - SWAT, CWI}
+module io::json::ADT
+
+data JSO
+	= jsnumber(real n)
+	| jsstring(str s)
+	| jsboolean(bool b)
+	| jsarray(list[JSO] xs)
+	| jsobject(map[JSO,JSO] kvs)
+	| jsnull()
+	;

rascal/src/io/json/Access.rsc

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+@contributor{Vadim Zaytsev - vadim@grammarware.net - SWAT, CWI}
+module io::json::Access
+
+import io::json::ADT;
+import util::Math;
+
+public real gimmeReal(jsnumber(n)) = n;
+public default real gimmeReal(JSO x) = 0.0;
+
+public int gimmeInt(jsnumber(n)) = toInt(n);
+public default int gimmeInt(JSO x) = 0;
+
+public str gimmeString(jsstring(s)) = s;
+public default str gimmeString(JSO x) = "";
+
+public bool gimmeBool(jsboolean(b)) = b;
+public default bool gimmeBool(JSO x) = false;
+
+public list[JSO] gimmeArray(jsarray(xs)) = xs;
+public default list[JSO] gimmeArray(JSO x) = [];
+
+public map[JSO,JSO] gimmeMap(jsobject(kvs)) = kvs;
+public default map[JSO,JSO] gimmeMap(JSO x) = ();
+
+public JSO gimmeNull(JSO x) = jsnull(); // well, if this is what you are asking...

rascal/src/io/json/Parser.rsc

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+@contributor{Vadim Zaytsev - vadim@grammarware.net - SWAT, CWI}
+module io::json::Parser
+
+import io::json::ADT;
+import io::json::Syntax;
+import IO;
+import String;
+import ParseTree;
+import util::Math;
+
+public JSO loc2jso(loc l) = str2jso(readFile(l));
+
+JSO str2jso(str s) = basic2jso(parse(#JSONBasicType,trim(s)));
+
+JSO basic2jso((JSONBasicType)`<JSONNumber v>`) = str2num("<v>");
+JSO basic2jso((JSONBasicType)`<JSONString v>`) = str2str("<v>");
+JSO basic2jso((JSONBasicType)`<JSONBoolean v>`) = str2bool("<v>");
+JSO basic2jso((JSONBasicType)`<JSONArray v>`) = jsarray(arr2array(v));
+JSO basic2jso((JSONBasicType)`<JSONObject v>`) = jsobject(obj2object(v));
+JSO basic2jso((JSONBasicType)`<JSONNull v>`) = jsnull();
+default JSO basic2jso(JSONBasicType t)
+{
+	println("wtf?!");
+	return jsnull();
+}
+
+JSO str2num(str s) = jsnumber(toReal(s)); // TODO so that it recognizes ints? (not crucial)
+JSO str2str(str s) = jsstring(s);
+
+JSO str2bool("true") = jsboolean(true);
+default JSO str2bool(str s) = jsboolean(false);
+
+list[JSO] arr2array((JSONArray)`[<{JSONBasicType ","}* vs>]`) = [basic2jso(v) | JSONBasicType v <- vs];
+
+map[JSO,JSO] obj2object((JSONObject)`{<{JSONKeyValue ","}* kvs>}`) = (basic2jso(kv.key):basic2jso(kv.val) | JSONKeyValue kv <- kvs);

rascal/src/io/json/Syntax.rsc

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+@contributor{Vadim Zaytsev - vadim@grammarware.net - SWAT, CWI}
+module io::json::Syntax
+
+layout L = WS;
+lexical WS = [\ \n\r\t]* !>> [\ \n\r\t];
+
+start syntax JSONData = JSONBasicType;
+
+syntax JSONBasicType
+	= JSONNumber
+	| JSONString
+	| JSONBoolean
+	| JSONArray
+	| JSONObject
+	| JSONNull
+	;
+
+syntax JSONNumber = "-"? Digits ("." Digits)?;
+lexical Digits = [0-9]+ !>> [0-9];
+
+syntax JSONString = DoubleQuotedString;
+lexical DoubleQuotedString = [\"] DQSElement* [\"]; //"
+lexical DQSElement = ![\"] | [\\][\"] ; //"
+
+syntax JSONBoolean = "false" | "true" ;
+
+syntax JSONArray = "[" {JSONBasicType ","}* "]";
+
+syntax JSONObject = "{" {JSONKeyValue ","}* "}";
+syntax JSONKeyValue = JSONBasicType key ":" JSONBasicType val;
+
+syntax JSONNull = "null" ;