Create new library / ieee_proposed not found.

Hello,

i'm doing a design which uses sfixed, so it needs the IEEE_PROPOSED library in the fixed_pkg_c.vhdl file exactly, so i've run into problems by generating a Testbench for my project that the modelsim complains, of not having that library:

** Error: C:/Users/Alfonso/Desktop/PFC/altera/fixed_pkg_c.vhdl(22): Library ieee_proposed not found.# ** Error: C:/Users/Alfonso/Desktop/PFC/altera/fixed_pkg_c.vhdl(23): (vcom-1136) Unknown identifier "IEEE_PROPOSED".# ** Error: C:/Users/Alfonso/Desktop/PFC/altera/fixed_pkg_c.vhdl(28): VHDL Compiler exiting# ** Error: E:/altera/11.1sp2/modelsim_ase/win32aloem/vcom failed.

while the compilation ends succesfully.

I think is something related to libraries for some google i've done.

Thank you

Alfonso.