understanding shader mat4 * vec4 calculation​

this blog from: http://stackoverflow.com/questions/13745334/understanding-shader-mat4-vec4-calculation

understanding shader mat4 * vec4 calculation

can someone confirm following calculation, please? :)

in normal android opengl shader the computation:

mat4 a;
vec3 p;

vec3 pos = (a * vec4(p,1.0)).xyz;

would be calculated like this:

pos.x = a0 * p.x + a1 * p.y + a2 * p.z + a3 * 1.0;
pos.y = a4 * p.x + a5 * p.y + a6 * p.z + a7 * 1.0;
pos.z = a8 * p.x + a9 * p.y + a10 * p.z + a11 * 1.0;

is this correct? or did I miss something? every help is highly appreciated.

answer1:

Ok actually I've found a reliable source: http://www.khronos.org/files/opengles_shading_language.pdf

vec3 v, u;
mat3 m;

And

u = m * v;

is equivalent to

u.x = m[0].x * v.x  +  m[1].x * v.y  +  m[2].x * v.z;
u.y = m[0].y * v.x  +  m[1].y * v.y  +  m[2].y * v.z;
u.z = m[0].z * v.x  +  m[1].z * v.y  +  m[2].z * v.z;

Therefore

vec3 v, u;
mat4 m;

And

u = (mat * vec4(v,1.0)).xyz

should be equivalent to

u.x = m[0].x * v.x  +  m[1].x * v.y  +  m[2].x * v.z + m[3].x * 1;
u.y = m[0].y * v.x  +  m[1].y * v.y  +  m[2].y * v.z + m[3].y * 1;
u.z = m[0].z * v.x  +  m[1].z * v.y  +  m[2].z * v.z + m[3].z * 1;

Please correct me if I'm wrong though.