cited

Clamp

float clamp(float x, float minVal, float maxVal)  
vec2 clamp(vec2 x, vec2 minVal, vec2 maxVal)  
vec3 clamp(vec3 x, vec3 minVal, vec3 maxVal)  
vec4 clamp(vec4 x, vec4 minVal, vec4 maxVal)

The clamp function returns x if it is larger than minVal and smaller than maxVal. In case x is smaller than minVal, minVal is returned. If x is larger than maxVal, maxVal is returned. The input parameters can be floating scalars or float vectors. In case of float vectors the operation is done component-wise.

float clamp(float x, float minVal, float maxVal)  
vec2 clamp(vec2 x, float minVal, float maxVal)  
vec3 clamp(vec3 x, float minVal, float maxVal)  
vec4 clamp(vec4 x, flfloat minVal, float maxVal)

There is also a variation of the clamp function where the second and third parameters are always a floating scalars.