float2 and the second parameter ...

So I was trying out the Toon Ramp listed here:
http://docs.unity3d.com/Manual/SL-SurfaceShaderLightingExamples.html
and the Team Fortress 2 Shader listed here:
http://wiki.unity3d.com/index.php/TeamFortress2Shader

In both cases if I use it straight as listed, I get the error:
Shader error in 'Custom/RampShadows': incorrect number of arguments to numeric-type constructor

Here are the problem lines from both:

fixed3 ramp = tex2D(_RampTex, float2(NdotL* atten)).rgb;

half3...

float2 and the second parameter ...