The Dimesum blog
How a money share tracking app is actually built: the ledger that cannot drift, the bill maths, the parser we deleted, and the art direction behind the dumplings.
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Money
Settle up: how to clear group expenses in fewer transfers
What settle up means and how to do it: net every balance instead of repaying receipts, clear a group in at most n-1 transfers, and confirm both sides agree.
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Money
Six money bugs in multi-currency expense splitting
A multi-currency expense splitting audit found six money bugs a green test suite never saw. Read every defect, its cause, and the fix that deleted an engine.
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Design
Four illustration styles, and the one that ships
Dimesum drew four illustration styles and shipped one. The brand art direction rule: a colour that cannot become a token cannot be re-themed.
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Money
Why editing a shared expense must restate the split
Editing a shared expense in Dimesum means restating the whole split, so fixing a typo never pulls in a flatmate who joined later or flattens 70/30 to 50/50.
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Engineering
The append-only ledger that keeps split-expense balances exact
Dimesum posts every split expense to an append-only ledger, so balances become a projection you can delete and rebuild instead of a number that drifts.