R Under development (unstable) (2026-02-09 r89390 ucrt) -- "Unsuffered Consequences"
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Platform: x86_64-w64-mingw32/x64

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> 
>  objfun <- function(x) {
+      stopifnot(is.numeric(x))
+      stopifnot(length(x) == 2)
+      f <- expression(5 * x1 + x1^2 - x2^2 + (1 / 100) * (x1^4 + x2^4))
+      g1 <- D(f, "x1")
+      g2 <- D(f, "x2")
+      h11 <- D(g1, "x1")
+      h12 <- D(g1, "x2")
+      h22 <- D(g2, "x2")
+      x1 <- x[1]
+      x2 <- x[2]
+      f <- eval(f)
+      g <- c(eval(g1), eval(g2))
+      B <- rbind(c(eval(h11), eval(h12)), c(eval(h12), eval(h22)))
+      list(value = f, gradient = g, hessian = B)
+  }
> 
>  library(trust)
> 
>  tout <- trust(objfun, c(0, 0), 1, 5, blather = TRUE)
>  tout
$value
[1] -30.93159

$gradient
[1]  0.000000e+00 -5.329071e-15

$hessian
         [,1] [,2]
[1,] 2.616708    0
[2,] 0.000000    4

$argument
[1] -2.266988 -7.071068

$converged
[1] TRUE

$iterations
[1] 8

$argpath
          [,1]      [,2]
[1,]  0.000000  0.000000
[2,] -1.000000  0.000000
[3,] -1.718447 -1.866503
[4,] -2.001409 -5.856479
[5,] -2.274119 -7.594949
[6,] -2.266994 -7.120719
[7,] -2.266988 -7.071582
[8,] -2.266988 -7.071068

$argtry
          [,1]      [,2]
[1,] -1.000000  0.000000
[2,] -1.718447 -1.866503
[3,] -2.001409 -5.856479
[4,] -2.274119 -7.594949
[5,] -2.266994 -7.120719
[6,] -2.266988 -7.071582
[7,] -2.266988 -7.071068
[8,] -2.266988 -7.071068

$steptype
[1] "hard-easy" "hard-hard" "easy-easy" "Newton"    "Newton"    "Newton"   
[7] "Newton"    "Newton"   

$accept
[1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE

$r
[1] 1 2 4 4 4 4 4 4

$rho
[1] 0.9975000 0.9725735 0.7278016 0.5975543 1.0576207 1.0068411 1.0000727
[8] 0.5634280

$valpath
[1]   0.000000  -3.990000  -8.914432 -28.375535 -30.341199 -30.926623 -30.931588
[8] -30.931588

$valtry
[1]  -3.990000  -8.914432 -28.375535 -30.341199 -30.926623 -30.931588 -30.931588
[8] -30.931588

$preddiff
[1] -4.000000e+00 -5.063301e+00 -2.673957e+01 -3.289515e+00 -5.535295e-01
[6] -4.930875e-03 -5.294725e-07 -6.305533e-15

$stepnorm
[1] 1.000000e+00 2.000000e+00 3.999996e+00 1.759730e+00 4.742834e-01
[6] 4.913654e-02 5.144691e-04 5.614950e-08

> 
>  (tout$stepnorm / tout$r)[tout$accept & tout$steptype != "Newton"]
[1] 1.0000000 1.0000000 0.9999991
> 
> 
> proc.time()
   user  system elapsed 
   0.17    0.06    0.17