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