```
PrependTo(s, item)
```

prepend

`item`

to value of`s`

and sets`s`

to the result.

Assign `s`

to a list

```
>> s = {1, 2, 4, 9}
{1,2,4,9}
```

Add a new value at the beginning of the list:

```
>> PrependTo(s, 0)
{0,1,2,4,9}
```

The value assigned to `s`

has changed:

```
>> s
{0,1,2,4,9}
```

`PrependTo`

works with a head other than `List`

:

```
>> y = f(a, b, c)
>> PrependTo(y, x)
f(x,a,b,c)
>> y
f(x,a,b,c)
```

{a, b} is not a variable with a value, so its value cannot be changed.

```
>> PrependTo({a, b}, 1)
PrependTo({a,b},1)
```

a is not a variable with a value, so its value cannot be changed.

```
>> PrependTo(a, b)
PrependTo(a,b)
>> x = 1 + 2
3
```

Nonatomic expression expected at position `1`

in `PrependTo`

```
>> PrependTo(x, {3, 4})
PrependTo(x,{3,4})
```

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