# Logic

Boolean operations and conditional execution.

## Boolean Operators

```forth
1 1 and   ( 1 )
0 1 or    ( 1 )
1 not     ( 0 )
1 0 xor   ( 1 )
1 1 nand  ( 0 )
0 0 nor   ( 1 )
```

## Conditional Execution

Execute a quotation if condition is true:

```forth
{ "kick" s . } coin ?     ( 50% chance )
{ 0.5 gain } step 0 = ?   ( only on step 0 )
```

Execute if false:

```forth
{ "snare" s . } coin !?   ( if NOT coin )
```

## If-Else

```forth
{ "kick" s } { "snare" s } coin ifelse .
```

Stack: `(true-quot false-quot bool --)`

## Pick

Choose from multiple quotations:

```forth
{ 60 } { 64 } { 67 } step 3 mod pick note
```

Stack: `(quot1 quot2 ... quotN n -- result)`

## Apply

Execute a quotation unconditionally:

```forth
{ 2 * } apply   ( doubles top of stack )
```

## Examples

Conditional parameter:

```forth
"kick" s
  { 0.8 } { 0.4 } iter 2 mod = ifelse gain
.
```

Multi-way branching:

```forth
"synth" s
  { c4 } { e4 } { g4 } { c5 } step 4 mod pick note
.
```

## Words

| Word | Stack | Description |
|------|-------|-------------|
| `and` | (a b -- bool) | Logical and |
| `or` | (a b -- bool) | Logical or |
| `not` | (a -- bool) | Logical not |
| `xor` | (a b -- bool) | Exclusive or |
| `nand` | (a b -- bool) | Not and |
| `nor` | (a b -- bool) | Not or |
| `?` | (quot bool --) | Execute if true |
| `!?` | (quot bool --) | Execute if false |
| `ifelse` | (t-quot f-quot bool --) | If-else |
| `pick` | (..quots n --) | Execute nth quotation |
| `apply` | (quot --) | Execute unconditionally |