GLSL shader, point sprite, lookup texture

I’m trying to use a texture to control the size of some point sprites. This code does not compile. I’m trying to simply read one of the color values (red would be fine) in a texture and use it to control the size of a point sprite. Any help would be greatly appreciated.

uniform sampler2DRect displacement;

uniform float time;

uniform vec4 color

void main() {
    float value = texture1D(displacement, gl_MultiTexCoord0.x).x;
    gl_Position   = gl_ModelViewProjectionMatrix * gl_Vertex;
	float size    = gl_Normal.x;
    gl_PointSize  = size * value * 100.00;
    gl_FrontColor = gl_Color;

What errors are you getting?

In xcode it tells me the shader did not compile because of a syntax error.

i am learning glsl shader at the moment now, so i am not totally sure, but i think that you cant not access textures in the .vert.

but also try
float value = texture2DRect(displacement, gl_MultiTexCoord0.x).x;

as displacement is declared as a sampler2DRect and it getting converted to a 1d
could be the synatx error.