Fixed parameters for optimize

// Wrapper function to enable holding of parameters in Optimize
Function OptimizeWrapper(Wave xw, String holdString)
    if(strlen(holdString) != numpnts(xw))
        abort "strlen(holdString) must be equal to npnts(xw)"
    endif
    
    //use hold string as a mask to split xw into xw and pw, later reassemble
    //pass holdString as bit mask as first parameter in pw to optimizing function.
    //optfunc will reassemble
    
    Make/O/N=0/FREE xw_split, pw_split
    
    Variable bitmask = 0
    Variable i
    for(i=0;i<strlen(holdString);i+=1)
        if(stringmatch(holdString[i], "0"))
            InsertPoints/V=(xw[i]) numpnts(xw_split), 1, xw_split
        elseif(stringmatch(holdString[i], "1"))
            InsertPoints/V=(xw[i]) numpnts(pw_split), 1, pw_split
            bitmask = bitmask | 2^i
        else
            abort "Illegal holdString"
        endif
    endfor
    
    InsertPoints/V=(bitmask) 0, 1, pw_split //store bitmask in pos 0 of pw
 
    Optimize/A/M={2,1}/D=4/X=xw_split/R=xw_split optFuncHoldWrap, pw_split //TODO: The wrapper now hard-codes the actual function that I'd like to optimize. How do I pass an optFunc FUNCREF to optFuncHoldWrap?
End
 
Function optFuncHoldWrap(Wave pw_split, Wave xw_split)
    Variable bitmask = pw_split[0]
    Variable numPar = numpnts(xw_split)+numpnts(pw_split)-1
    
    //Reassemble xw
    Make/O/FREE/N=0 xw, pw
    Variable i, cx=0, cp=0
    for(i=0;i<numPar;i+=1)
        if(bitmask & 2^i)
            InsertPoints/V=(pw_split[cp+1]) numpnts(xw), 1, xw
            cp+=1
        else
            InsertPoints/V=(xw_split[cx]) numpnts(xw), 1, xw
            cx+=1
        endif
    endfor
    
    return optFunc(pw, xw) //Hard-coded
End
 
 
Function optFunc(Wave pw, Wave xw)
 //(...)
End