M.V. Hutz
361f529bdc
## Summary - Added doc comments across the codebase: `pkg/lambda`, `pkg/saccharine`, `pkg/codec`, `pkg/engine`, `pkg/iterator`, `pkg/set`, `pkg/convert`, `internal/registry`, and `cmd/lambda`. - Made lambda and saccharine expression structs use public fields instead of getters, matching `go/ast` conventions. - Removed superfluous constructors for saccharine and lambda expression/statement types in favor of struct literals. - Consolidated saccharine token constructors into a single `NewToken` function. - Removed the unused `trace` package. ## Test plan - [x] `go build ./...` passes. - [x] `go test ./...` passes. - [ ] Verify `go doc` output renders correctly for documented packages. Reviewed-on: #45 Co-authored-by: M.V. Hutz <git@maximhutz.me> Co-committed-by: M.V. Hutz <git@maximhutz.me>
40 lines
1.1 KiB
Go
40 lines
1.1 KiB
Go
package normalorder
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import "git.maximhutz.com/max/lambda/pkg/lambda"
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// ReduceOnce attempts to apply a single reduction to a lambda expression.
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// It returns (1) the final expression (reduced, or not), and (2) whether or not
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// a reduction was applied.
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//
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// If a reduction is not applied, it returns the original expression.
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func ReduceOnce(e lambda.Expression) (lambda.Expression, bool) {
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switch e := e.(type) {
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case lambda.Abstraction:
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body, reduced := ReduceOnce(e.Body)
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if reduced {
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return lambda.Abstraction{Parameter: e.Parameter, Body: body}, true
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}
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return e, false
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case lambda.Application:
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if fn, fnOk := e.Abstraction.(lambda.Abstraction); fnOk {
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return lambda.Substitute(fn.Body, fn.Parameter, e.Argument), true
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}
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abs, reduced := ReduceOnce(e.Abstraction)
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if reduced {
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return lambda.Application{Abstraction: abs, Argument: e.Argument}, true
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}
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arg, reduced := ReduceOnce(e.Argument)
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if reduced {
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return lambda.Application{Abstraction: e.Abstraction, Argument: arg}, true
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}
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return e, false
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default:
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return e, false
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}
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}
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