# Removed Functions

Functions which once existed in the Stan language and have since been replaced or removed are listed here.

## multiply_log and binomial_coefficient_log functions

Removed: Currently two non-conforming functions ending in suffix _log.

Replacement: Replace multiply_log(...) with lmultiply(...). Replace binomial_coefficient_log(...) with lchoose(...).

Removed In: Stan 2.33

## get_lp() function

Removed: The built-in no-argument function get_lp() is deprecated.

Replacement: Use the no-argument function target() instead.

Removed In: Stan 2.33

## fabs function

Removed: The unary function fabs is deprecated.

Replacement: Use the unary function abs instead. Note that the return type for abs is different for integer overloads, but this replacement is safe due to Stan’s type promotion rules.

Removed In: Stan 2.33

These covariance functions have been replaced by those described in Gaussian Process Covariance Functions

With magnitude $$\alpha$$ and length scale $$l$$, the exponentiated quadratic kernel is:

$k(x_i, x_j) = \alpha^2 \exp \left(-\dfrac{1}{2\rho^2} \sum_{d=1}^D (x_{i,d} - x_{j,d})^2 \right)$

matrix cov_exp_quad(row_vectors x, real alpha, real rho)
The covariance matrix with an exponentiated quadratic kernel of x.

Available since 2.16, deprecated since 2.20, removed in in 2.33

matrix cov_exp_quad(vectors x, real alpha, real rho)
The covariance matrix with an exponentiated quadratic kernel of x.

Available since 2.16, deprecated since 2.20, removed in in 2.33

matrix cov_exp_quad(array[] real x, real alpha, real rho)
The covariance matrix with an exponentiated quadratic kernel of x.

Available since 2.16, deprecated since 2.20, removed in in 2.33

matrix cov_exp_quad(row_vectors x1, row_vectors x2, real alpha, real rho)
The covariance matrix with an exponentiated quadratic kernel of x1 and x2.

Available since 2.18, deprecated since 2.20, removed in in 2.33

matrix cov_exp_quad(vectors x1, vectors x2, real alpha, real rho)
The covariance matrix with an exponentiated quadratic kernel of x1 and x2.

Available since 2.18, deprecated since 2.20, removed in in 2.33

matrix cov_exp_quad(array[] real x1, array[] real x2, real alpha, real rho)
The covariance matrix with an exponentiated quadratic kernel of x1 and x2.

Available since 2.18, deprecated since 2.20, removed in in 2.33

## Real arguments to logical operators operator&&, operator||, and operator!

Removed: A nonzero real number (even NaN) was interpreted as true and a zero was interpreted as false.

Replacement: Explicit x != 0 comparison is preferred instead.

Removed In: Stan 2.34