error in filter design coding

hello everyone,

please anyone could help me to fix these errors.i have tried but im getting so many erors after that.thank you very much.

#ifndef _Convert_h
#define _Convert_h
Waveform SignalToWaveform(const Signal& s);
Signal WaveformToSignal(const Waveform& w);
ComplexWaveform WaveformToComplexWaveform(const Waveform& w);
Waveform ComplexWaveformMagToWaveform(const ComplexWaveform& c);
Waveform ComplexWaveformRealToWaveform(const ComplexWaveform& c);
#endif


3.cpp
c:\vc98\include\convert.h(4) : error C2143: syntax error : missing ',' before '&'
c:\vc98\include\convert.h(4) : error C2059: syntax error : '&'
c:\vc98\include\convert.h(5) : error C2146: syntax error : missing ';' before identifier 'WaveformToSignal'
c:\vc98\include\convert.h(5) : error C2501: 'Signal' : missing storage-class or type specifiers
c:\vc98\include\convert.h(5) : fatal error C1004: unexpected end of file found
Error executing cl.exe.
3.exe - 5 error(s), 0 warning(s)

You are failing to include the header that declares Signal.

thank you sir.now i can run the code ready.