## Faint amusement from arrows

In logic, we talk about propositions, giving them names, say *p* or *q*. For example, *p* might be the proposition 'it is raining', and *q* the proposition 'I will get wet'. Then to represent the proposition '*if* it is raining *then* I will get wet', we can say '*p* IMPLIES *q*', which is often written with a double-arrow:

In ASCII, this can be approximated by 'p => q'.

In full, this operator has the following truth table:

p | q | p => q |
---|---|---|

T | T | T |

T | F | F |

F | T | T |

F | F | T |

(This appears slightly strange, but the only way we can disprove the claim '*p* implies *q*' is if *p* happens but *q* doesn't.)

In many programming languages, you can ask whether object *x* is 'less than' object *y*, where this is natural for things like numbers, but can be extended to objects of other types. In particular, for Boolean objects, it's very common for *False* to be 'less than' *True*. If we look at the truth table for , represented in many languages as 'x <= y', we find

x | y | x <= y |
---|---|---|

F | F | T |

F | T | T |

T | F | F |

T | T | T |

The witty thing (and recall that this only provides *faint* amusement) is that we can compare these tables to conclude:

p <= q means p => q.

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