Symbolic matrix mutiplication error (Ryacas)

soln <- Solve(n/2*(2-exp(-lambda12*Tf)-exp(-lambda18*Tf))==d , n) 
X <- yacas(soln)$text

 X <- expression(list(n == 382/1.625))
 res <- eval(X[[1]][[2]][[3]])
 res
 [1] 235.0769

as.list(X)
# [[1]]
# list(n == 382/1.625)

as.list(X[[1]])
# [[1]]
# list
# 
# [[2]]
# n == 382/1.625

as.list(X[[1]][[2]])
# [[1]]
# `==`
# 
# [[2]]
# n
# 
# [[3]]
# 382/1.625

L = 4;
for (i = 1; i <= p.length - 4; i++)
{
   ...
}

L = 4;
for (i = 1; i <= p.length - 4; i++)
{
    j = i + 3;
    ...
}

L = 4;
for (i = 1; i <= p.length - 4; i++)
{
    j = i + 3;
    m[i,j] = MAXINT;
    for (k = i; k <= j - 1; k++)
    { 
        // get the cost of splitting at `k`, 
        // i.e. chains (i, k) and (k + 1, j)
    }
}

> mat1 * mat2
expression(list(list(x^2 + 6, x^2 + 12 * x), list(x^4 + 3 * x, 
    x^4 + 6 * x^2)))

a = 1:3;
b = 2:4;

c = a.*b; 
% c = [2 6 12], element-wise multiplication c(j) = a(j)*b(j)

c = b'*a;  
% c = [2 4 5; 3 6 9; 4 8 12]
% standard matrix multiplication of vectors
% c(i,j) = a(i) + b(j)

c = bsxfun(@times, b', a)
% c = [2 4 5; 3 6 9; 4 8 12]
% bsxfun applies the function (in this case @times) to b' and a

 % b' in singleton in the 2nd dimension, a is singleton in the 1st dimension
 % Use repmat to perform the expansion to the correct size
 repmat(b', 1, size(a,2)) .* repmat(a, size(b',1), 1)
 % Equivalent to...
 repmat(b', 1, 3) .* repmat(a, 3, 1)
 % Equivalent to...
 [2 2 2; 3 3 3; 4 4 4] .* [1 2 3; 1 2 3; 1 2 3]   
 % = [2 4 5; 3 6 9; 4 8 12] the same as b'*a

c = a.*b'; % Error: Matrix dimensions must agree.
c = b'.*a; % Error: Matrix dimensions must agree.

c = a.*b'; % [2 4 5; 3 6 9; 4 8 12] the same as bsxfun(@times, a, b')
c = b'.*a; % [2 4 5; 3 6 9; 4 8 12] the same as bsxfun(@times, b', a)
% These two are equivalent also because order of operations is irrelevant
% We can see this by thinking about the expansion discussed above

c = a(:).*b(:); % c = [2; 6; 12] always a column vector

typeof(NA)
## [1] "logical"

f <- matrix(list(), 4, 4)

f[[1, 1]] <- z^2 * exp(-z) / (1 - exp(-z))

psi <- list()

psi[[1]] <- z^2 * exp(-z) / (1 - exp(-z))

Eval(f[[i, 1]], list(z = 1))
## [1] 0.2432798

z <- 1
Eval(f[[i, 1]])

vignette("Ryacas")

demo(package = "Ryacas")

# install.packages('Ryacas')
library(Ryacas)    

z <- Sym("z")

psi <- list()
psi[[1]] <- z^2 * exp(-z) / (1 - exp(-z))
psi[[2]] <- z^2 * exp(-z) / (1 - exp(-z)) * log(z)
psi[[3]] <- z^2 * exp(-z) / (1 - exp(-z)) * log(z)^2

f <- matrix(list(), 4, 4)
f[[1,1]] <- z^2 * exp(-z) / (1 - exp(-z))
for(i in 2:4) {
  f[[i, 1]] <- deriv(psi[[i-1]], z)
  j <- 2
  while(j <= i) {
    f[[i, j]] <- deriv(f[[i, j-1]] / f[[j-1, j-1]], z)
    j <- j + 1
  }
}

i <- 2
deriv(psi[[i-1]], z)
f[[i, 1]]

Eval(f[[i, 1]], list(z = 1))