Cg shader using discard

Shader "Custom/Cg shader using discard"
{
	SubShader 
	{
		Pass 
		{
			Cull Off

			CGPROGRAM
			
			#pragma vertex vert
			#pragma fragment frag

			struct vertexInput
			{
				float4 vertex:POSITION ;
			};
			struct vertexOutput
			{
				float4 pos:SV_POSITION;
				float4 posInObjectCoords:TEXCOORD0 ; 
			};

			vertexOutput vert(vertexInput input)
			{
				vertexOutput output;
				output.pos = mul(UNITY_MATRIX_MVP,input.vertex);
				output.posInObjectCoords = input.vertex;

				return output;
			}

			float4 frag(vertexOutput input):COLOR
			{
				if(input.posInObjectCoords.y>0.0)
				{
					discard;
				}
				return float4(0.0,1.0,0.0,1.0);
			}
			ENDCG
		}
	}
}