diff --git a/demo.srd b/demo.srd
index 7576a85..7f603ff 100644
--- a/demo.srd
+++ b/demo.srd
@@ -1,27 +1,82 @@
 (init
 	# Compute viewport size
-	(if (gt width height)
+	(if (cmp-gt width height)
 		(
-			(set vp-height height)
-			(set vp-width (mul height (div 16 9)))
-			(set vp-x (div (sub width vp-width) 2))
+			(set vp-height $height)
+			(set vp-width (mul $height (div 16 9)))
+			(set vp-x (div (sub $width $vp-width) 2))
 			(set vp-y 0)
 		)(
-			(set vp-width width)
-			(set vp-height (div width (div 16 9)))
-			(set vp-y (div (sub height vp-height) 2))
+			(set vp-width $width)
+			(set vp-height (div $width (div 16 9)))
+			(set vp-y (div (sub $height $vp-height) 2))
 			(set vp-x 0)
 		)
 	)
 
 	(program prg-fullscreen "fullscreen.v.glsl")
+
+	(call scene-init)
 	(call dof-init)
 )
 
 (frame
 	(profiling "Frame render"
-		{ FIXME: other stages }
-		(call dof-main { FIXME: args here })
+		(call scene-main)
+		(call dof-main tx-scene-output tx-scene-depth)
+	)
+)
+
+
+################################################################################
+# Scene
+
+(fn scene-init ()
+	(texture tx-scene-output rgb-f16 vp-width vp-height)
+	(texture tx-scene-depth r-f16 vp-width vp-height)
+	{ NOT IMPLEMENTED
+		(framebuffer rt-scene
+			(colors tx-scene-output tx-scene-depth))
+	}
+
+	(program prg-scene-p1 "scene.f.glsl")
+	# NOT IMPLEMENTED (set-uniforms prg-scene-p1 1 $vp-width $vp-height)
+	(pipeline pl-scene-p1 prg-fullscreen prg-scene-p1)
+
+	{ NOT IMPLEMENTED
+		(odbg tx-scene-output hdr "Scene output")
+		(odbg tx-scene-depth depth "Scene depth")
+	}
+)
+
+(fn scene-main ()
+	(profiling "Scene render"
+		{ NOT IMPLEMENTED
+			(set-uniforms prg-scene-p1 0 $time)
+			(set-uniforms prg-scene-p1 2
+				(get-input "camera-pos-x")
+				(get-input "camera-pos-y")
+				(get-input "camera-pos-z")
+			)
+			(set-uniforms prg-scene-p1 3
+				(get-input "camera-lookat-x")
+				(get-input "camera-lookat-y")
+				(get-input "camera-lookat-z")
+			)
+			(set-uniforms prg-scene-p1 4
+				(get-input "camera-up-x")
+				(get-input "camera-up-y")
+				(get-input "camera-up-z")
+			)
+			(set-uniforms prg-scene-p1 5
+				(get-input "camera-nearplane")
+			)
+			# FIXME MOAR UNIFORMS!
+			(use-pipeline pl-scene-p1)
+			(use-framebuffer rt-scene)
+		}
+		(viewport 0 0 $vp-width $vp-height)
+		(fullscreen)
 	)
 )
 
@@ -30,33 +85,43 @@
 
 (fn dof-init ()
 	# Sampler used for the inputs
-	(sampler dof-sampler
-		(mipmaps no)
-		(wrapping clamp-edge)
-		(sampling linear)
-		(lod 0 0)	
-	)
+	{ NOT IMPLEMENTED
+		(sampler dof-sampler
+			(mipmaps no)
+			(wrapping clamp-edge)
+			(sampling linear)
+			(lod 0 0)	
+		)
+	}
 
 	# Texture & RT for pass 1
 	(texture tx-dof-pass1 rgb-f16 vp-width vp-height)
-	(framebuffer rt-dof-pass1 (colors tx-dof-pass1))
+	{ NOT IMPLEMENTED
+		(framebuffer rt-dof-pass1 (colors tx-dof-pass1))
+	}
 
 	# Texture & RT for pass 2
 	(texture tx-dof-pass2 rgb-f16 vp-width vp-height)
-	(framebuffer rt-dof-pass2 (colors tx-dof-pass2))
-	(alias tx-dof-output tx-dof-pass2)
+	{ NOT IMPLEMENTED
+		(framebuffer rt-dof-pass2 (colors tx-dof-pass2))
+	}
+	# MAYBE ? (alias tx-dof-output tx-dof-pass2)
 
 	# Output debugging
-	(odbg tx-dof-pass1 hdr "DoF - First pass")
-	(odbg tx-dof-pass2 hdr "DoF - Output")
+	{ NOT IMPLEMENTED
+		(odbg tx-dof-pass1 hdr "DoF - First pass")
+		(odbg tx-dof-pass2 hdr "DoF - Output")
+	}
 
 	# Programs
 	(program prg-dof-pass1 "dof-pass1.f.glsl")
 	(program prg-dof-pass2 "dof-pass2.f.glsl")
-	(set-uniforms-integer prg-dof-pass1 0 1)
-	(set-uniforms-integer prg-dof-pass1 1 1)
-	(set-uniforms-integer prg-dof-pass2 0 1)
-	(set-uniforms-integer prg-dof-pass2 1 1)
+	{ NOT IMPLEMENTED
+		(set-uniforms-integer prg-dof-pass1 0 1)
+		(set-uniforms-integer prg-dof-pass1 1 1)
+		(set-uniforms-integer prg-dof-pass2 0 1)
+		(set-uniforms-integer prg-dof-pass2 1 1)
+	}
 
 	# Pipelines
 	(pipeline pl-dof-pass1 prg-fullscreen prg-dof-pass1)
@@ -70,24 +135,28 @@
 	(input dof-samples 16)
 
 	# Input overrides
-	(ui-overrides "Post-processing" "Depth of Field"
-		(float dof-sharp-distance (min 0) (max 1000) (step .1))
-		(float dof-sharp-range (min 0) (max 500) (step .1))
-		(float dof-falloff (min 0) (max 500) (step .1))
-		(float dof-max-blur (min 1) (max 64) (step .1))
-		(int dof-samples (min 1) (max 64) (step .1))
-	)
+	{ NOT IMPLEMENTED
+		(ui-overrides "Post-processing" "Depth of Field"
+			(float dof-sharp-distance (min 0) (max 1000) (step .1))
+			(float dof-sharp-range (min 0) (max 500) (step .1))
+			(float dof-falloff (min 0) (max 500) (step .1))
+			(float dof-max-blur (min 1) (max 64) (step .1))
+			(int dof-samples (min 1) (max 64) (step .1))
+		)
+	}
 )
 
 (fn dof-set-uniforms (prog)
-	(set-uniforms prog 2 (
-		(get-input dof-sharp-distance)
-		(get-input dof-sharp-range)
-		(get-input dof-falloff)
-		(get-input dof-max-blur)
-	))
-	(set-uniforms prog 3 ((get-input dof-samples)))
-	(set-uniforms prog 4 (vp-width vp-height time))
+	{ NOT IMPLEMENTED
+		(set-uniforms prog 2
+			(get-input dof-sharp-distance)
+			(get-input dof-sharp-range)
+			(get-input dof-falloff)
+			(get-input dof-max-blur)
+		)
+		(set-uniforms prog 3 (get-input dof-samples))
+		(set-uniforms prog 4 $vp-width $vp-height $time)
+	}
 )
 
 (fn dof-main (in-image in-depth)
@@ -104,8 +173,10 @@
 		# Second pass
 		(call dof-set-uniforms prg-dof-pass2)
 		(use-texture 0 tx-dof-pass1 dof-sampler)
+
 		(use-pipeline pl-dof-pass2)
 		(use-framebuffer rt-dof-pass2)
+		(viewport 0 0 $vp-width $vp-height)
 		(fullscreen)
 	)
 )
diff --git a/opast.cc b/opast.cc
index 5398795..7e00c2a 100644
--- a/opast.cc
+++ b/opast.cc
@@ -97,8 +97,11 @@ A_Node* opast::ASTVisitorBrowser(
 
 	    // Nodes that do not have children
 	    case A_Node::EXPR_ID: case A_Node::EXPR_CONST:
+	    case A_Node::EXPR_INPUT:
 	    case A_Node::OP_PROGRAM: case A_Node::OP_PIPELINE:
-	    case A_Node::OP_INPUT:
+	    case A_Node::OP_INPUT: case A_Node::OP_FULLSCREEN:
+	    case A_Node::OP_USE_FRAMEBUFFER: case A_Node::OP_USE_PIPELINE:
+	    case A_Node::OP_USE_PROGRAM: case A_Node::OP_USE_TEXTURE:
 		break;
 
 	    // Profile instruction
@@ -168,6 +171,24 @@ A_Node* opast::ASTVisitorBrowser(
 		break;
 	    }
 
+	    // Viewport instruction
+	    case A_Node::OP_VIEWPORT:
+	    {
+		auto& n( (T_ViewportInstrNode&) node );
+		auto c = child;
+		for ( int i = 0 ; i < 4 ; i ++ ) {
+			T_ViewportInstrNode::E_Parameter p{
+				T_ViewportInstrNode::E_Parameter( i ) };
+			if ( n.hasParameter( p ) ) {
+				if ( c == 0 ) {
+					return &n.parameter( p );
+				}
+				c --;
+			}
+		}
+		break;
+	    }
+
 	}
 	return nullptr;
 }
@@ -314,6 +335,7 @@ struct T_ParserImpl_
 {
 	enum class E_InstrType {
 		CALL ,
+		FULLSCREEN ,
 		IF ,
 		INPUT ,
 		PIPELINE ,
@@ -321,6 +343,11 @@ struct T_ParserImpl_
 		PROGRAM ,
 		SET ,
 		TEXTURE ,
+		USE_FRAMEBUFFER ,
+		USE_PIPELINE ,
+		USE_PROGRAM ,
+		USE_TEXTURE ,
+		VIEWPORT ,
 	};
 
 	const T_KeyValueTable< T_String , E_InstrType > instrMap{ ([]() {
@@ -330,6 +357,7 @@ struct T_ParserImpl_
 		} };
 
 		add( "call" , E_InstrType::CALL );
+		add( "fullscreen" , E_InstrType::FULLSCREEN );
 		add( "if" , E_InstrType::IF );
 		add( "input" , E_InstrType::INPUT );
 		add( "pipeline" , E_InstrType::PIPELINE );
@@ -337,6 +365,11 @@ struct T_ParserImpl_
 		add( "program" , E_InstrType::PROGRAM );
 		add( "set" , E_InstrType::SET );
 		add( "texture" , E_InstrType::TEXTURE );
+		add( "use-framebuffer" , E_InstrType::USE_FRAMEBUFFER );
+		add( "use-pipeline" , E_InstrType::USE_PIPELINE );
+		add( "use-program" , E_InstrType::USE_PROGRAM );
+		add( "use-texture" , E_InstrType::USE_TEXTURE );
+		add( "viewport" , E_InstrType::VIEWPORT );
 
 		return temp;
 	})( ) };
@@ -451,6 +484,15 @@ struct T_ParserImpl_
 	M_DPARSER_( Program );
 	M_DPARSER_( Set );
 	M_DPARSER_( Texture );
+	M_DPARSER_( UseFramebuffer );
+	M_DPARSER_( UsePipeline );
+	M_DPARSER_( UseProgram );
+	void parseUseCommon(
+			T_InstrListNode& instructions ,
+			T_SRDList const& input ,
+			T_UseInstrNode::E_Type type ) noexcept;
+	M_DPARSER_( UseTexture );
+	M_DPARSER_( Viewport );
 
 #undef M_DPARSER_
 
@@ -711,6 +753,15 @@ void T_ParserImpl_::parseInstructions(
 			M_CASE_( PROGRAM , Program );
 			M_CASE_( SET , Set );
 			M_CASE_( TEXTURE , Texture );
+			M_CASE_( USE_FRAMEBUFFER , UseFramebuffer );
+			M_CASE_( USE_PIPELINE , UsePipeline );
+			M_CASE_( USE_PROGRAM , UseProgram );
+			M_CASE_( USE_TEXTURE , UseTexture );
+			M_CASE_( VIEWPORT , Viewport );
+
+		    case E_InstrType::FULLSCREEN:
+			instructions.add< T_FullscreenInstrNode >( ).location( ) = iname.location( );
+			break;
 		}
 #undef M_CASE_
 	}
@@ -983,6 +1034,102 @@ M_INSTR_( Texture )
 
 /*----------------------------------------------------------------------------*/
 
+M_INSTR_( UseFramebuffer )
+{
+	parseUseCommon( instructions , input , T_UseInstrNode::FRAMEBUFFER );
+}
+
+M_INSTR_( UsePipeline )
+{
+	parseUseCommon( instructions , input , T_UseInstrNode::PIPELINE );
+}
+
+M_INSTR_( UseProgram )
+{
+	parseUseCommon( instructions , input , T_UseInstrNode::PROGRAM );
+}
+
+void T_ParserImpl_::parseUseCommon(
+		T_InstrListNode& instructions ,
+		T_SRDList const& input ,
+		T_UseInstrNode::E_Type type ) noexcept
+{
+	if ( input.size( ) == 1 || input[ 1 ].type( ) != E_SRDTokenType::WORD ) {
+		errors.addNew( "resource identifier expected" ,
+				input[ input.size( ) == 1 ? 0 : 1 ].location( ) );
+		return;
+	}
+	if ( input.size( ) > 2 ) {
+		errors.addNew( "too many arguments" , input[ 2 ].location( ) );
+	}
+
+	auto& instr{ instructions.add< T_UseInstrNode >( type , input[ 1 ] ) };
+	instr.location( ) = input[ 0 ].location( );
+}
+
+/*----------------------------------------------------------------------------*/
+
+M_INSTR_( UseTexture )
+{
+	if ( input.size( ) == 1 || !input[ 1 ].isInteger( ) ) {
+		errors.addNew( "bank number expected" ,
+				input[ input.size( ) == 1 ? 0 : 1 ].location( ) );
+		return;
+	}
+	if ( input[ 1 ].longValue( ) < 0 || input[ 1 ].longValue( ) > UINT32_MAX ) {
+		errors.addNew( "invalid bank number" , input[ 1 ].location( ) );
+		return;
+	}
+
+	if ( input.size( ) == 2 || input[ 2 ].type( ) != E_SRDTokenType::WORD ) {
+		errors.addNew( "texture identifier expected" ,
+				input[ input.size( ) == 2 ? 0 : 2 ].location( ) );
+		return;
+	}
+	if ( input.size( ) == 3 || input[ 3 ].type( ) != E_SRDTokenType::WORD ) {
+		errors.addNew( "sampler identifier expected" ,
+				input[ input.size( ) == 3 ? 0 : 3 ].location( ) );
+		return;
+	}
+	if ( input.size( ) > 4 ) {
+		errors.addNew( "too many arguments" , input[ 4 ].location( ) );
+	}
+
+	auto& instr{ instructions.add< T_UseTextureInstrNode >(
+			input[ 1 ] , input[ 2 ] , input[ 3 ] ) };
+	instr.location( ) = input[ 0 ].location( );
+}
+
+/*----------------------------------------------------------------------------*/
+
+M_INSTR_( Viewport )
+{
+	auto& instr{ instructions.add< T_ViewportInstrNode >( ) };
+	instr.location( ) = input[ 0 ].location( );
+
+	for ( auto i = 1u ; i < 5 ; i ++ ) {
+		T_ViewportInstrNode::E_Parameter p{
+			T_ViewportInstrNode::E_Parameter( i ) };
+		if ( input.size( ) < i ) {
+			T_StringBuilder sb;
+			sb << "missing ";
+			switch ( p ) {
+			    case T_ViewportInstrNode::PX: sb << "X"; break;
+			    case T_ViewportInstrNode::PY: sb << "Y"; break;
+			    case T_ViewportInstrNode::PWIDTH: sb << "width"; break;
+			    case T_ViewportInstrNode::PHEIGHT: sb << "height"; break;
+			}
+			sb << " parameter";
+			errors.addNew( std::move( sb ) , input[ 0 ].location( ) );
+			return;
+		} else {
+			instr.setParameter( p , parseExpression( instr , input[ i ] ) );
+		}
+	}
+}
+
+/*----------------------------------------------------------------------------*/
+
 P_ExpressionNode T_ParserImpl_::parseExpression(
 		A_Node& parent ,
 		T_SRDToken const& token ) noexcept
@@ -1012,6 +1159,20 @@ P_ExpressionNode T_ParserImpl_::parseOperation(
 		return {};
 	}
 
+	if ( opId.stringValue( ) == "get-input" ) {
+		if ( opList.size( ) == 1 || !opList[ 1 ].isText( ) ) {
+			errors.addNew( "input identifier expected" ,
+					opList[ opList.size( ) == 1 ? 0 : 1 ].location( ) );
+			return { };
+		}
+		if ( opList.size( ) > 2 ) {
+			errors.addNew( "too many arguments" , opList[ 2 ].location( ) );
+		}
+		auto node{ NewOwned< T_InputExprNode >( parent , opList[ 1 ] ) };
+		node->location( ) = opList[ 0 ].location( );
+		return node;
+	}
+
 	if ( binOpMap.contains( opId.stringValue( ) ) ) {
 		return parseBinOp( parent , opList ,
 				*binOpMap.get( opId.stringValue( ) ) );
diff --git a/opast.hh b/opast.hh
index 69fa112..092b833 100644
--- a/opast.hh
+++ b/opast.hh
@@ -25,12 +25,19 @@ class A_Node
 		//
 		OP_CALL ,	// Function call
 		OP_COND ,	// Conditional instruction
+		OP_FULLSCREEN ,	// Draw a fullscreen quad
 		OP_INPUT ,	// Input declaration
 		OP_PIPELINE ,	// Shader pipeline declaration
 		OP_PROFILE ,	// Profiling block
 		OP_PROGRAM ,	// Shader program declaration
 		OP_SET ,	// Set instruction
 		OP_TEXTURE ,	// Define texture
+		OP_VIEWPORT ,	// Set viewport
+		// "Use-<obj type>" instructions
+		OP_USE_FRAMEBUFFER ,
+		OP_USE_PIPELINE ,
+		OP_USE_PROGRAM ,
+		OP_USE_TEXTURE ,
 		// Unary operators
 		EXPR_NEG , EXPR_INV , EXPR_NOT ,
 		EXPR_SIN , EXPR_COS , EXPR_TAN ,
@@ -45,6 +52,7 @@ class A_Node
 		EXPR_CMP_LT , EXPR_CMP_LE ,
 		//
 		EXPR_ID ,	// Variable access
+		EXPR_INPUT ,	// Input value access
 		EXPR_CONST ,	// Numeric constant
 	};
 
@@ -361,6 +369,15 @@ class T_CondInstrNode : public A_InstructionNode
 		{ return *defaultCase_; }
 };
 
+// Fullscreen quad instruction
+class T_FullscreenInstrNode : public A_InstructionNode
+{
+    public:
+	T_FullscreenInstrNode( T_InstrListNode& parent ) noexcept
+		: A_InstructionNode( OP_FULLSCREEN , parent , E_InstrRestriction::INIT )
+	{ }
+};
+
 // Input declaration
 class T_InputInstrNode : public A_InstructionNode
 {
@@ -421,6 +438,11 @@ class T_PipelineInstrNode : public A_InstructionNode
 			idLocation_{ }
 	{ }
 
+	T_String const& id( ) const noexcept
+		{ return id_; }
+	T_SRDLocation const& idLocation( ) const noexcept
+		{ return idLocation_; }
+
 	// Add a program identifier. The token is assumed to be a valid word,
 	// and the list of programs is assumed not to be full. If the identifer
 	// is already in the pipeline's list, the location of the first
@@ -482,6 +504,11 @@ class T_ProgramInstrNode : public A_InstructionNode
 			path_( pathToken.stringValue( ) ) ,
 			pathLocation_( pathToken.location( ) )
 	{ }
+
+	T_String const& id( ) const noexcept
+		{ return id_; }
+	T_SRDLocation const& idLocation( ) const noexcept
+		{ return idLocation_; }
 };
 
 // Setting a global variable
@@ -495,12 +522,12 @@ class T_SetInstrNode : public A_InstructionNode
     public:
 	T_SetInstrNode( T_InstrListNode& parent ,
 			T_SRDToken const& idToken ) noexcept
-		: A_InstructionNode( OP_PROGRAM , parent ) ,
+		: A_InstructionNode( OP_SET , parent ) ,
 			id_( idToken.stringValue( ) ) ,
 			idLocation_( idToken.location( ) )
 	{ }
 
-	T_String const& identifier( ) const noexcept
+	T_String const& id( ) const noexcept
 		{ return id_; }
 	T_SRDLocation const& idLocation( ) const noexcept
 		{ return idLocation_; }
@@ -528,11 +555,16 @@ class T_TextureInstrNode : public A_InstructionNode
 			T_InstrListNode& parent ,
 			T_SRDToken const& id ,
 			E_TexType type ) noexcept
-		: A_InstructionNode( OP_PROGRAM , parent , E_InstrRestriction::FRAME ) ,
+		: A_InstructionNode( OP_TEXTURE , parent , E_InstrRestriction::FRAME ) ,
 			id_( id.stringValue( ) ) , idLocation_( id.location( ) ) ,
 			type_( type )
 	{ }
 
+	T_String const& id( ) const noexcept
+		{ return id_; }
+	T_SRDLocation const& idLocation( ) const noexcept
+		{ return idLocation_; }
+
 	void setWidth( P_ExpressionNode width ) noexcept
 		{ width_ = std::move( width ); }
 	bool hasWidth( ) const noexcept
@@ -548,6 +580,99 @@ class T_TextureInstrNode : public A_InstructionNode
 		{ return *height_; }
 };
 
+// Use-* instructions (framebuffers, programs, pipelines)
+// Also serves as the base for use-texture
+class T_UseInstrNode : public A_InstructionNode
+{
+    public:
+	enum E_Type {
+		FRAMEBUFFER , PIPELINE , PROGRAM , TEXTURE
+	};
+
+    private:
+	T_String id_;
+	T_SRDLocation idLocation_;
+
+    public:
+	T_UseInstrNode( T_InstrListNode& parent ,
+			const E_Type type ,
+			T_SRDToken const& identifier ) noexcept
+		: A_InstructionNode( ([type]() {
+				switch ( type ) {
+					case FRAMEBUFFER: return OP_USE_FRAMEBUFFER;
+					case PIPELINE: return OP_USE_PIPELINE;
+					case PROGRAM: return OP_USE_PROGRAM;
+					case TEXTURE: return OP_USE_TEXTURE;
+				}
+				std::abort( );
+			} )( ) , parent ) ,
+			id_( identifier.stringValue( ) ) ,
+			idLocation_( identifier.location( ) )
+	{ }
+
+	T_String const& id( ) const noexcept
+		{ return id_; }
+	T_SRDLocation const& idLocation( ) const noexcept
+		{ return idLocation_; }
+};
+
+// Texture/sampler use instructions
+class T_UseTextureInstrNode : public T_UseInstrNode
+{
+    private:
+	uint32_t bank_;
+	T_SRDLocation bankLocation_;
+	T_String samplerId_;
+	T_SRDLocation samplerIdLocation_;
+
+    public:
+	T_UseTextureInstrNode( T_InstrListNode& parent ,
+			T_SRDToken const& bank ,
+			T_SRDToken const& identifier ,
+			T_SRDToken const& sampler ) noexcept
+		: T_UseInstrNode( parent , TEXTURE , identifier ) ,
+			bank_( bank.longValue( ) ) ,
+			bankLocation_( bank.location( ) ) ,
+			samplerId_( sampler.stringValue( ) ) ,
+			samplerIdLocation_( sampler.location( ) )
+	{ }
+
+	uint32_t bank( ) const noexcept
+		{ return bank_; }
+	T_SRDLocation const& bankLocation( ) const noexcept
+		{ return bankLocation_; }
+
+	T_String const& samplerId( ) const noexcept
+		{ return samplerId_; }
+	T_SRDLocation const& samplerIdLocation( ) const noexcept
+		{ return samplerIdLocation_; }
+};
+
+// Viewport instruction
+class T_ViewportInstrNode : public A_InstructionNode
+{
+    public:
+	enum E_Parameter {
+		PX , PY , PWIDTH , PHEIGHT
+	};
+
+    private:
+	P_ExpressionNode parameters_[ 4 ];
+
+    public:
+	T_ViewportInstrNode( T_InstrListNode& parent ) noexcept
+		: A_InstructionNode( OP_VIEWPORT , parent ,
+				E_InstrRestriction::INIT )
+	{ }
+
+	void setParameter( const E_Parameter p , P_ExpressionNode height ) noexcept
+		{ parameters_[ int( p ) ] = std::move( height ); }
+	bool hasParameter( const E_Parameter p ) const noexcept
+		{ return bool( parameters_[ int( p ) ] ); }
+	A_ExpressionNode& parameter( const E_Parameter p ) const noexcept
+		{ return *parameters_[ int( p ) ]; }
+};
+
 /*============================================================================*/
 
 // A constant value
@@ -608,6 +733,27 @@ class T_IdentifierExprNode : public A_ExpressionNode
 		{ return id_; }
 };
 
+// Access to an input value
+class T_InputExprNode : public A_ExpressionNode
+{
+    private:
+	T_String id_;
+	T_SRDLocation idLocation_;
+
+    public:
+	T_InputExprNode( A_Node& parent ,
+			T_SRDToken const& token ) noexcept
+		 : A_ExpressionNode( EXPR_INPUT , parent ) ,
+			id_( token.stringValue( ) ) ,
+			idLocation_( token.location( ) )
+	{ }
+
+	T_String const& id( ) const noexcept
+		{ return id_; }
+	T_SRDLocation const& idLocation( ) const noexcept
+		{ return idLocation_; }
+};
+
 // A unary operator
 class T_UnaryOperatorNode : public A_ExpressionNode
 {