122 lines
3.0 KiB
Go
122 lines
3.0 KiB
Go
package saccharine
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import (
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"errors"
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"fmt"
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"git.maximhutz.com/max/lambda/pkg/iterator"
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"git.maximhutz.com/max/lambda/pkg/saccharine/ast"
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"git.maximhutz.com/max/lambda/pkg/saccharine/token"
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)
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type TokenIterator = iterator.Iterator[token.Token]
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func parseToken(i *TokenIterator, expected token.Type) (*token.Token, error) {
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i2 := i.Copy()
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if tok, err := i2.Next(); err != nil {
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return nil, err
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} else if tok.Type != expected {
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return nil, fmt.Errorf("expected token %v, got %v'", token.Name(expected), tok.Value)
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} else {
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i.Sync(i2)
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return &tok, nil
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}
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}
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func parseExpression(i *TokenIterator) (ast.Expression, error) {
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if abs, absErr := parseAbstraction(i); absErr == nil {
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return abs, nil
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} else if atm, atmErr := parseApplication(i); atmErr == nil {
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return atm, nil
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} else if app, appErr := parseAtom(i); appErr == nil {
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return app, nil
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} else {
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return nil, errors.Join(absErr, appErr, atmErr)
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}
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}
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func parseParameters(i *TokenIterator) ([]string, error) {
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i2 := i.Copy()
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variables := []string{}
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for {
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if tok, err := parseToken(i2, token.Atom); err != nil {
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break
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} else {
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variables = append(variables, tok.Value)
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}
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}
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i.Sync(i2)
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return variables, nil
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}
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func parseAbstraction(i *TokenIterator) (*ast.Abstraction, error) {
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i2 := i.Copy()
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if _, err := parseToken(i2, token.Slash); err != nil {
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return nil, fmt.Errorf("no function slash (col %d): %w", i2.MustGet().Index, err)
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} else if parameters, err := parseParameters(i2); err != nil {
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return nil, err
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} else if _, err = parseToken(i2, token.Dot); err != nil {
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return nil, fmt.Errorf("no function dot (col %d): %w", i2.MustGet().Index, err)
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} else if body, err := parseExpression(i2); err != nil {
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return nil, err
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} else {
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i.Sync(i2)
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return ast.NewAbstraction(parameters, body), nil
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}
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}
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func parseApplication(i *TokenIterator) (*ast.Application, error) {
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i2 := i.Copy()
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expressions := []ast.Expression{}
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if _, err := parseToken(i2, token.OpenParen); err != nil {
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return nil, fmt.Errorf("no openning brackets (col %d): %w", i2.MustGet().Index, err)
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}
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for {
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if exp, err := parseExpression(i2); err != nil {
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break
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} else {
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expressions = append(expressions, exp)
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}
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}
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if _, err := parseToken(i2, token.CloseParen); err != nil {
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return nil, fmt.Errorf("no closing brackets (col %d): %w", i2.MustGet().Index, err)
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}
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if len(expressions) == 0 {
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return nil, fmt.Errorf("application has no arguments")
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}
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i.Sync(i2)
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return ast.NewApplication(expressions[0], expressions[1:]), nil
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}
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func parseAtom(i *TokenIterator) (*ast.Atom, error) {
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if tok, err := parseToken(i, token.Atom); err != nil {
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return nil, fmt.Errorf("no variable (col %d): %w", i.Index(), err)
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} else {
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return ast.NewAtom(tok.Value), nil
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}
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}
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func Parse(tokens []token.Token) (ast.Expression, error) {
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i := iterator.Of(tokens)
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exp, err := parseExpression(i)
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if err != nil {
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return nil, err
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}
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if !i.Done() {
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return nil, fmt.Errorf("expected EOF, found more code (col %d)", i.MustGet().Index)
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}
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return exp, nil
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}
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