8 * Section 4.3.4 (Inputs) of the GLSLLangSpec.1.50.09 4.3.4 Inputs says:
10 * Vertex shader inputs can only be float, floating-point
11 * vectors, matrices, signed and unsigned integers and integer vectors.
12 * Vertex shader inputs can also form arrays of these types, but not
26 gl_Position = vec4(a[0] + a[1]