Substitute symbol for value

`subs(sym, nms, vls)`

- sym
Expression

- nms
Names of symbols (see Details)

- vls
Values that

`nms`

is substituted with (see Details)

Two different ways to call this function is supported:

Supplying

`nms`

as a named list and omitting`vls`

. If two components have the same name, the behaviour is undefined.Supplying both

`nms`

and`vls`

See Examples.

```
if (has_sympy()) {
x <- symbol('x')
e <- 2*x^2
e
subs(e, "x", "2")
subs(e, x, 2)
subs(e, list(x = 2))
A <- matrix_sym(2, 2, "a")
B <- matrix_sym(2, 2, "b")
e <- A %*% A
subs(e, A, B)
}
#> c: ⎡ 2 ⎤
#> ⎢ b₁₁ + b₁₂⋅b₂₁ b₁₁⋅b₁₂ + b₁₂⋅b₂₂⎥
#> ⎢ ⎥
#> ⎢ 2 ⎥
#> ⎣b₁₁⋅b₂₁ + b₂₁⋅b₂₂ b₁₂⋅b₂₁ + b₂₂ ⎦
```