functions in matrix.i - T

    TDsolve(c, d, e, b)  
 or TDsolve(c, d, e, b, which=which)  


returns the solution to the tridiagonal system:  
   D(1)*x(1)       + E(1)*x(2)                       = B(1)  
   C(1:-1)*x(1:-2) + D(2:-1)*x(2:-1) + E(2:0)*x(3:0) = B(2:-1)  
                     C(0)*x(-1)      + D(0)*x(0)     = B(0)  
(i.e.- C is the subdiagonal, D the diagonal, and E the superdiagonal;  
C and E have one fewer element than D, which is the same length as  
both B and x)  
B may have additional dimensions, in which case the returned x  
will have the same additional dimensions.  The WHICH dimension of B,  
and of the returned x is the one of length n which participates  
in the matrix solve.  By default, WHICH=1, so that the equations  
being solved involve B(,..) and x(+,..).  
Non-positive WHICH counts from the final dimension (as for the  
sort and transpose functions), so that WHICH=0 involves B(..,)  
and x(..,+).  
The C, D, and E arguments may be either scalars or vectors; they  
will be broadcast as appropriate.  
Interpreted function, defined at i0/matrix.i   line 36