dictionary: Added lookupType function for convenient lookup and setting of value

of the specified type

src/OpenFOAM/db/dictionary/dictionary.H

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
-    \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2017 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -334,7 +334,19 @@ public:
             ) const;
 
             //- Find and return a T,
-            //  if not found return the given default value
+            //  if not found throw a fatal error.
+            //  If recursive, search parent dictionaries.
+            //  If patternMatch, use regular expressions.
+            template<class T>
+            T lookupType
+            (
+                const word&,
+                bool recursive=false,
+                bool patternMatch=true
+            ) const;
+
+            //- Find and return a T,
+            //  if not found return the given default value.
             //  If recursive, search parent dictionaries.
             //  If patternMatch, use regular expressions.
             template<class T>

src/OpenFOAM/db/dictionary/dictionaryTemplates.C

@@ -28,6 +28,30 @@ License
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
+template<class T>
+T Foam::dictionary::lookupType
+(
+    const word& keyword,
+    bool recursive,
+    bool patternMatch
+) const
+{
+    const entry* entryPtr = lookupEntryPtr(keyword, recursive, patternMatch);
+
+    if (entryPtr == nullptr)
+    {
+        FatalIOErrorInFunction
+        (
+            *this
+        )   << "keyword " << keyword << " is undefined in dictionary "
+            << name()
+            << exit(FatalIOError);
+    }
+
+    return pTraits<T>(entryPtr->stream());
+}
+
+
 template<class T>
 T Foam::dictionary::lookupOrDefault
 (