# propeller.problems.PSB2.middle-character documentation

## Generated by Codox

# Propeller 0.3.0

# propeller.problems.PSB2.middle-character

MIDDLE CHARACTER from PSB2

Given a string, return the middle character as a string if it is odd length; return the two middle characters as a string if it is even length.

Source: https://arxiv.org/pdf/2106.06086.pdf

### -main

`(-main & args)`

Runs propel-gp, giving it a map of arguments.

### error-function

`(error-function argmap data individual)`

Finds the behaviors and errors of an individual: Error is 0 if the value and the program’s selected behavior match, or 1 if they differ, or 1000000 if no behavior is produced. The behavior is here defined as the final top item on the STRING stack.

### instructions

Stack-specific instructions, input instructions, close, and constants

### random-int

`(random-int)`

Random integer between -100 and 100

### train-and-test-data

Data taken from https://zenodo.org/record/5084812