Outline Playground — GCP Type Inference

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OutlineA structurally-typed language powered by GCP inference

Most typed languages make you write types so the compiler can check them.
Outline flips this: the compiler figures out every type from how you use values — down to field names, HOF chains, and multi-level structural constraints.

What makes it different

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Duck Typing with Iron-Clad Types

GCP synthesises the full entity type from how functions access fields — zero declarations, zero annotations, zero boilerplate.

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Backward Constraint Propagation

Type constraints flow backwards through HOF chains. A level of inference no other practical language achieves without explicit generic parameters.

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Future this — Self-Type Extension Chaining

Methods that return this always resolve to the concrete receiver type — covariant self-type without F-bounded generics.

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Full Dynamic Inference, No Limits

Church numerals, generic HOF combinators, deeply nested entity chains — GCP infers it all.

Open the 📖 Tutorial to walk through every feature·Press ▶ Run to see live type inference

Execution Result

Press ▶ Run to execute your code

No console output — use print(x)

✓

No errors detected

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⟨T⟩ Outline Playground