13.12 Brackets array syntax

Before Stan 2.26, arrays were declared by writing syntax after the variable. As of version 2.26, the old syntax has been deprecated and replaced with a keyword-based syntax.

Deprecated: The use of array declarations like

int n[5];
real a[3, 4];
real<lower=0> z[5, 4, 2];
vector[7] mu[3];
matrix[7, 2] mu[15, 12];
cholesky_factor_cov[5, 6] mu[2, 3, 4];

Replacement: The use of the array keyword, which replaces the above examples with

array[5] int n;
array[3, 4] real a;
array[5, 4, 2] real<lower=0> z;
array[3] vector[7] mu;
array[15, 12] matrix[7, 2] mu;
array[2, 3, 4] cholesky_factor_cov[5, 6] mu;