Tag
Cats Core · Part 3
I knew how to combine two error reports. Monoid gives an empty batch a useful result, and foldMap takes the same idea to a shopping cart: turn each line into a contribution, then combine the totals.
Cats Core · Part 2
I could see Validated collecting errors, but I wanted to see the method call behind it. I made its Semigroup argument explicit, then supplied a combination rule for my own structured errors.
Scala and the JVM · Part 17
I connect Future composition and recovery to the map/flatMap pattern, reproduce one-worker starvation safely, and finish with the distinction between a business Left and a failed Future.
Scala and the JVM · Part 16
I replace String failures with a sealed family of domain errors, keep Either composition unchanged, and choose human-readable messages only at the display boundary.
Scala and the JVM · Part 15
I unpack AnyFunSuite from a Java developer’s perspective, test returned Right and Left values, check thrown exceptions with intercept, and verify that independent expectations catch real mistakes.
Cats Core · Part 1
I started learning Cats Core with a small policy form. The same mapN operation first combines optional fields, then collects useful validation errors with Validated.
Scala and the JVM · Part 14
From Java-style exception handling to composable Scala results: capture a throwing conversion, understand map versus flatMap, write the same chain with for, and recover only from a specific failure.
Scala and the JVM · Part 13
From a Java/Spring perspective, I build Scala Either from explicit Left/Right cases to map, flatMap and a for-comprehension, with three verified lookup outcomes and failure reasons that survive the chain.
Scala and the JVM · Part 12
Coming from Java, a String with a lookup method looks wild. I unpack Scala 2 implicit classes into an ordinary wrapper, then show how the compiler can supply its repository argument too.
Scala and the JVM · Part 11
From multiple parameter lists to compiler-supplied repository arguments: real missing and ambiguous implicit errors, explicit fixes, and the difference between a missing dependency and a missing policy.