62 lines
1.5 KiB
Go
62 lines
1.5 KiB
Go
package convert
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import (
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"fmt"
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"git.maximhutz.com/max/lambda/pkg/lambda"
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"git.maximhutz.com/max/lambda/pkg/saccharine/ast"
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)
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func convertAtom(n *ast.Atom) lambda.Expression {
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return lambda.NewVariable(n.Name)
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}
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func convertAbstraction(n *ast.Abstraction) lambda.Expression {
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result := SaccharineToLambda(n.Body)
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parameters := n.Parameters
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// If the function has no parameters, it is a thunk. Lambda calculus still
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// requires _some_ parameter exists, so generate one.
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if len(parameters) == 0 {
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freeVars := lambda.GetFreeVariables(result)
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freshName := lambda.GenerateFreshName(freeVars)
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parameters = append(parameters, freshName)
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}
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for i := len(parameters) - 1; i >= 0; i-- {
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result = lambda.NewAbstraction(parameters[i], result)
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}
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return result
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}
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func convertApplication(n *ast.Application) lambda.Expression {
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result := SaccharineToLambda(n.Abstraction)
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arguments := []lambda.Expression{}
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for _, argument := range n.Arguments {
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convertedArgument := SaccharineToLambda(argument)
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arguments = append(arguments, convertedArgument)
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}
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for _, argument := range arguments {
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result = lambda.NewApplication(result, argument)
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}
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return result
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}
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func SaccharineToLambda(n ast.Expression) lambda.Expression {
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switch n := n.(type) {
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case *ast.Atom:
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return convertAtom(n)
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case *ast.Abstraction:
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return convertAbstraction(n)
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case *ast.Application:
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return convertApplication(n)
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default:
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panic(fmt.Errorf("unknown expression type: %T", n))
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}
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}
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