# Sample LBA Inputs

These examples are for use with the perl LBA emulator provided at the bottom of Context Sensitive Languages. That page also contains a description of what a LBA is and how it works.

This machine accepts strings of the form ${\displaystyle \{a^{n}b^{n}c^{n}d^{n}|n\geq 0\}}$.
Note that in this example, the input must be bounded by one "_" on each side as a tape delimiter.

```:States:
start findA findB findC findD reset halt
:Start State:
start
:Accept States:
halt
:alphabet:
_ a b c d \$
:tape bound:
1 0
:rules:
start     _     findA     _     right
findA     \$     findA     \$     right
findA     a     findB     \$     right
findA     _     halt      _     left
findB     \$     findB     \$     right
findB     a     findB     a     right
findB     b     findC     \$     right
findC     \$     findC     \$     right
findC     b     findC     b     right
findC     c     findD     \$     right
findD     \$     findD     \$     right
findD     c     findD     c     right
findD     d     reset     \$     left
reset     \$     reset     \$     left
reset     a     reset     a     left
reset     b     reset     b     left
reset     c     reset     c     left
reset     d     reset     d     left
reset     _     findA     _     right
```

Some sample inputs:
These accept:

```_ a a a b b b c c c d d d _
```
```_ _
```
```_ a b c d _
```

These reject:

```_ a a a b b b c c d d d _
```
```_ a c _
```
```_ a b b c c d d _
```

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