Support ? and ?? operations.

expreduce/builtin_system.go

@@ -330,6 +330,9 @@ func GetSystemDefinitions() (defs []Definition) {
 			if !ok {
 				return false, ""
 			}
+			if params.es == nil {
+				return true, "Definiton[<WITHOUT_CONTEXT>]"
+			}
 			def, isd := params.es.defined[sym.Name]
 			if !isd {
 				return true, "Null"
@@ -519,8 +522,16 @@ func GetSystemDefinitions() (defs []Definition) {
 				return this
 			}
 
+			context, contextPath := ActualStringFormArgs(es)
+			stringParams := ToStringParams{
+				form: "OutputForm",
+				context: context,
+				contextPath: contextPath,
+				previousHead: "<TOPLEVEL>",
+				es: es,
+			}
 			for i := 1; i < len(this.Parts); i++ {
-				fmt.Printf("%s", this.Parts[i].String())
+				fmt.Printf("%s", this.Parts[i].StringForm(stringParams))
 			}
 			fmt.Printf("\n")
 			return NewSymbol("System`Null")
@@ -784,5 +795,6 @@ func GetSystemDefinitions() (defs []Definition) {
 		Name: "Defer",
 		OmitDocumentation: true,
 	})
+	defs = append(defs, Definition{Name: "Information"})
 	return
 }

expreduce/definition.go

@@ -68,5 +68,5 @@ func (def *Def) StringForm(defSym *Symbol, params ToStringParams) string {
 		)
 		buffer = append(buffer, e.StringForm(params))
 	}
-	return strings.Join(buffer[:], "\n")
+	return strings.Join(buffer[:], "\n\n")
 }

expreduce/evalstate.go

@@ -134,6 +134,7 @@ func (es *EvalState) Init(loadAllDefs bool) {
 		es.MarkSeen("System`Complex")
 		es.MarkSeen("System`Integers")
 		es.MarkSeen("System`Break")
+		es.MarkSeen("System`LongForm")
 
 		es.MarkSeen("System`Exp")
 		es.MarkSeen("System`AppellF1")

expreduce/interp.go

@@ -337,7 +337,7 @@ func ParserExprConv(expr *wl.Expression) Ex {
 			e,
 			ParserExprConv(expr.Expression2),
 		})
-	case 140:
+	case wl.ExpressionMessageName:
 		return NewExpression([]Ex{
 			NewSymbol("System`MessageName"),
 			ParserTokenConv(expr.Token),
@@ -452,6 +452,17 @@ func ParserExprConv(expr *wl.Expression) Ex {
 			NewSymbol("System`Sqrt"),
 			ParserExprConv(expr.Expression),
 		})
+	case wl.ExpressionInfo:
+		return E(
+			S("Information"),
+			ParserTagConv(expr.Tag),
+		)
+	case wl.ExpressionInfoShort:
+		return E(
+			S("Information"),
+			ParserTagConv(expr.Tag),
+			E(S("Rule"), S("LongForm"), S("False")),
+		)
 	}
 	log.Fatalf("System`UnParsed: %+v %+v %+v", expr.Token, expr.Case, expr)
 	return nil

expreduce/resources/system.m

@@ -325,3 +325,14 @@
 
 Definition::usage = "`Definition[sym]` renders the attributes, downvalues, and default value of `sym`.";
 Attributes[Definition] = {HoldAll, Protected};
+
+Information::usage = "`Information[sym]` renders the usage, attributes, downvalues, and default value of `sym`.";
+Information[sym_Symbol, LongForm->useLongForm_] := (
+    Print[sym::usage];
+    If[useLongForm,
+        Print[""];
+        Print[Definition[sym]];
+    ];
+);
+Information[sym_Symbol] := Information[sym, LongForm->True];
+Attributes[Information] = {HoldAll, Protected, ReadProtected};