M.V. Hutz
f3b9137d75
Closes #26 - Added -i flag to select interpreter (lambda or debruijn) - Created debruijn package with Expression interface - Variable contains index and optional label - Abstraction contains only body (no parameter) - Application structure remains similar - Implemented De Bruijn reduction without variable renaming - Shift operation handles index adjustments - Substitute replaces by index instead of name - Abstracted Engine into interface with two implementations - LambdaEngine: original named variable engine - DeBruijnEngine: new index-based engine - Added conversion functions between representations - LambdaToDeBruijn: converts named to indexed - DeBruijnToLambda: converts indexed back to named - SaccharineToDeBruijn: direct saccharine to De Bruijn - Updated main to switch engines based on -i flag - All test samples pass with both engines Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
44 lines
1.2 KiB
Go
44 lines
1.2 KiB
Go
package convert
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import (
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"git.maximhutz.com/max/lambda/pkg/debruijn"
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"git.maximhutz.com/max/lambda/pkg/lambda"
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)
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// LambdaToDeBruijn converts a lambda expression to De Bruijn index representation.
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func LambdaToDeBruijn(expr lambda.Expression) debruijn.Expression {
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return lambdaToDeBruijn(expr, []string{})
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}
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func lambdaToDeBruijn(expr lambda.Expression, context []string) debruijn.Expression {
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switch e := expr.(type) {
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case *lambda.Variable:
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index := findIndex(e.Value(), context)
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return debruijn.NewVariable(index, e.Value())
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case *lambda.Abstraction:
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newContext := append([]string{e.Parameter()}, context...)
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body := lambdaToDeBruijn(e.Body(), newContext)
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return debruijn.NewAbstraction(body)
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case *lambda.Application:
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abs := lambdaToDeBruijn(e.Abstraction(), context)
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arg := lambdaToDeBruijn(e.Argument(), context)
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return debruijn.NewApplication(abs, arg)
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default:
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return nil
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}
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}
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// findIndex returns the De Bruijn index for a variable name in the context.
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// Returns the index if found, or -1 if the variable is free.
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func findIndex(name string, context []string) int {
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for i, v := range context {
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if v == name {
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return i
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}
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}
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return -1
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}
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