81 lines
2.1 KiB
Go
81 lines
2.1 KiB
Go
package saccharine
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import (
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"fmt"
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"git.maximhutz.com/max/lambda/pkg/iterator"
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)
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func isVariableToken(t Token) bool {
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return t.Type == TokenVariable
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}
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func ParseExpression(i *iterator.Iterator[Token]) (Node, error) {
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token, err := i.Pop()
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if err != nil {
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return nil, fmt.Errorf("could not get next token: %w", err)
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}
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switch token.Type {
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case TokenVariable:
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return NewVariable(token.Value), nil
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case TokenDot:
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return nil, fmt.Errorf("token '.' found without a corresponding slash (column %d)", token.Index)
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case TokenSlash:
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tokens := i.PopWhile(isVariableToken)
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variables := []string{}
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for _, token := range tokens {
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variables = append(variables, token.Value)
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}
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if dot, dotErr := i.Pop(); dotErr != nil {
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return nil, fmt.Errorf("could not find parameter terminator: %w", dotErr)
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} else if dot.Type != TokenDot {
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return nil, fmt.Errorf("expected '.', got '%v' (column %d)", dot.Value, dot.Index)
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}
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body, bodyErr := ParseExpression(i)
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if bodyErr != nil {
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return nil, fmt.Errorf("could not parse function body: %w", bodyErr)
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}
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return NewAbstraction(variables, body), nil
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case TokenOpenParen:
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fn, fnErr := ParseExpression(i)
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if fnErr != nil {
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return nil, fmt.Errorf("could not parse call function: %w", fnErr)
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}
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args := []Node{}
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for {
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if next, nextErr := i.Peek(); nextErr == nil && next.Type == TokenCloseParen {
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break
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}
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arg, argErr := ParseExpression(i)
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if argErr != nil {
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return nil, fmt.Errorf("could not parse call argument: %w", argErr)
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}
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args = append(args, arg)
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}
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closing, closingErr := i.Pop()
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if closingErr != nil {
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return nil, fmt.Errorf("could not parse call terminating parenthesis: %w", closingErr)
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} else if closing.Type != TokenCloseParen {
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return nil, fmt.Errorf("expected call terminating parenthesis, got '%v' (column %v)", closing.Value, closing.Index)
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}
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return NewApplication(fn, args), nil
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}
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return nil, fmt.Errorf("unexpected token '%v' (column %d)", token.Value, token.Index)
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}
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func GetTree(tokens []Token) (Node, error) {
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return ParseExpression(iterator.New(tokens))
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}
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