View Compilation Error

0_0_20602277_12353.cpp:1:1: error: 'function' does not name a type
 function g=csimage(f,param)
 ^
0_0_20602277_12353.cpp:3:1: error: expected unqualified-id before 'if'
 if param<0
 ^
0_0_20602277_12353.cpp:5:1: error: 'end' does not name a type
 end
 ^
0_0_20602277_12353.cpp:7:1: error: expected unqualified-id before '[' token
 [U,V]=dftuv(PQ(1),PQ(2));
 ^
0_0_20602277_12353.cpp:8:1: error: 'D0' does not name a type
 D0=param*PQ(2);
 ^
0_0_20602277_12353.cpp:9:1: error: 'H' does not name a type
 H=exp(-(U.^2+V.^2)/(2*(D0^2)));
 ^
0_0_20602277_12353.cpp:10:1: error: 'g' does not name a type
 g=dftfilt(f,H);
 ^