# 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

## Exponentiated quadratic covariance functions

These covariance functions have been replaced by those described in Gaussian Process Covariance Functions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