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001101 / accounting.sql
Created February 18, 2017 09:08 — forked from NYKevin/accounting.sql
Basic double-entry bookkeeping system, for PostgreSQL.
CREATE TABLE accounts(
id serial PRIMARY KEY,
name VARCHAR(256) NOT NULL
);
CREATE TABLE entries(
id serial PRIMARY KEY,
description VARCHAR(1024) NOT NULL,
amount NUMERIC(20, 2) NOT NULL CHECK (amount > 0.0),
-- Every entry is a credit to one account...
@pthariensflame
pthariensflame / IndexedState.md
Last active June 15, 2022 18:42
An introduction to the indexed state monad in Haskell, Scala, and C#.

The Indexed State Monad in Haskell, Scala, and C#

Have you ever had to write code that made a complex series of succesive modifications to a single piece of mutable state? (Almost certainly yes.)

Did you ever wish you could make the compiler tell you if a particular operation on the state was illegal at a given point in the modifications? (If you're a fan of static typing, probably yes.)

If that's the case, the indexed state monad can help!

Motivation