resource backsubstitution ()

int n; getarg (1,n)

string[20] namea; getarg(2,namea)
string[20] nameb; getarg(3,nameb)

file filea = open(namea, READ)
file fileb = open(nameb, READ)

real a [n,n];     real b [n];   real x [n] 

op  pipechan [n+1] (real data)

# Einlesen der Matrix und des Vektors
for [i=1 to n] {
	for [j = 1 to n] { 
    read(filea,a[i,j])
}
}
for [i= 1 to n] { 
	  read(fileb,b[i]) 
}

process pipe [i=1 to n] {
    real sum, xvalue
    sum = 0
    for [j = 1 to i-1] {    receive pipechan[i](xvalue)
                            send pipechan[i+1](xvalue)
                            sum += a[i,j] * xvalue
    }
    x[i] = (b[i] - sum)/a[i,i]
    send pipechan[i+1](x[i])
}


process writer  {
    real x
    for [i=1 to n] { receive pipechan[n+1](x); writes(x,"    ")}
    write()
}
end