break

ast_string.go

@@ -125,3 +125,7 @@ func (as *AstStringer) visitWhileStmt(w *WhileStmt) {
 	w.body.accept(as)
 	as.str.WriteString(")")
 }
+
+func (as *AstStringer) visitBreakStmt(b *BreakStmt) {
+	as.str.WriteString("(break)")
+}

glox.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bufio"
+	"fmt"
 	"log"
 	"os"
 )
@@ -51,7 +52,7 @@ func (gl *Glox) run(source []byte) {
 
 	stmts, _ := newParser(tokens).parse()
 
-	// fmt.Println(AstStringer{stmts: stmts})
+	fmt.Println(AstStringer{stmts: stmts})
 
 	gl.Interpreter.interpret(stmts)
 }

interpreter.go

@@ -10,6 +10,7 @@ import (
 type Interpreter struct {
 	env    *Environment
 	errors []error
+	brk    bool
 }
 
 type RuntimeError struct {
@@ -22,7 +23,7 @@ func (re *RuntimeError) Error() string {
 }
 
 func newInterpreter() *Interpreter {
-	return &Interpreter{env: newEnvironment(nil)}
+	return &Interpreter{env: newEnvironment(nil), errors: []error{}, brk: false}
 }
 
 func (i *Interpreter) interpret(stmts []Stmt) []error {
@@ -180,12 +181,21 @@ func (i *Interpreter) visitBlockStmt(b *BlockStmt) {
 	i.env = newEnvironment(parentEnv)
 
 	for _, stmt := range b.stmts {
+
+		if i.brk {
+			break
+		}
+
 		stmt.accept(i)
 	}
 
 	i.env = parentEnv
 }
 
+func (i *Interpreter) visitBreakStmt(b *BreakStmt) {
+	i.brk = true
+}
+
 func (i *Interpreter) visitIfStmt(iff *IfStmt) {
 	if isTruthy(i.evaluate(iff.expr)) {
 		iff.then.accept(i)
@@ -214,7 +224,14 @@ func (i *Interpreter) visitEnvStmt(e *EnvStmt) {
 
 func (i *Interpreter) visitWhileStmt(w *WhileStmt) {
 	for isTruthy(i.evaluate(w.cond)) {
+
+		if i.brk {
+			i.brk = false
+			break
+		}
+
 		w.body.accept(i)
+
 	}
 }
 

parser.go

@@ -71,6 +71,7 @@ func (p *Parser) varDecl() Stmt {
 //	| whileStmt
 //	| printStmt
 //	| blockStmt
+//	| breakStmt
 //	| ifStmt
 //	| env
 func (p *Parser) statement() Stmt {
@@ -94,6 +95,10 @@ func (p *Parser) statement() Stmt {
 		return p.whileStmt()
 	}
 
+	if p.match(BREAK) {
+		return p.breakStmt()
+	}
+
 	return p.exprStmt()
 }
 
@@ -134,6 +139,12 @@ func (p *Parser) blockStmt() Stmt {
 	return &BlockStmt{stmts}
 }
 
+// breakStmt -> break ";"
+func (p *Parser) breakStmt() Stmt {
+	p.consume(SEMICOLON, "Expect ';' after break.")
+	return &BreakStmt{}
+}
+
 // if -> "if" "(" expression ")" statement ("else" statement)?
 func (p *Parser) ifStmt() Stmt {
 	name := p.previous()
@@ -304,7 +315,7 @@ func (p *Parser) primary() Expr {
 		return &Grouping{expr}
 	}
 
-	// p.panic(&ParseError{p.peek(), "Expect expression"})
+	p.panic(&ParseError{p.peek(), "Expect expression"})
 
 	return nil
 }

scanner.go

@@ -43,6 +43,7 @@ const (
 
 	// keywords
 	AND
+	BREAK
 	CLASS
 	ENV
 	ELSE
@@ -65,6 +66,7 @@ const (
 
 var keywords = map[string]TokenType{
 	"and":    AND,
+	"break":  BREAK,
 	"class":  CLASS,
 	"else":   ELSE,
 	"false":  FALSE,

stmt.go

@@ -8,6 +8,7 @@ type StmtVisitor interface {
 	visitBlockStmt(b *BlockStmt)
 	visitEnvStmt(e *EnvStmt)
 	visitWhileStmt(w *WhileStmt)
+	visitBreakStmt(b *BreakStmt)
 }
 
 type Stmt interface {
@@ -46,6 +47,8 @@ type WhileStmt struct {
 	body Stmt
 }
 
+type BreakStmt struct{}
+
 func (i *IfStmt) stmt()    {}
 func (e *EnvStmt) stmt()   {}
 func (vs *VarStmt) stmt()  {}
@@ -53,6 +56,7 @@ func (es *ExprStmt) stmt() {}
 func (p *PrintStmt) stmt() {}
 func (b *BlockStmt) stmt() {}
 func (w *WhileStmt) stmt() {}
+func (b *BreakStmt) stmt() {}
 
 func (p *PrintStmt) accept(v StmtVisitor) {
 	v.visitPrintStmt(p)
@@ -81,3 +85,7 @@ func (e *EnvStmt) accept(v StmtVisitor) {
 func (w *WhileStmt) accept(v StmtVisitor) {
 	v.visitWhileStmt(w)
 }
+
+func (b *BreakStmt) accept(v StmtVisitor) {
+	v.visitBreakStmt(b)
+}

tests/while.lox

@@ -0,0 +1,28 @@
+var iterator = 100;
+
+{
+    while (iterator > 0) {
+       {
+         print iterator;
+        iterator = iterator - 2;
+       }
+    }
+}
+
+
+{
+    while (iterator < 100) {
+        {
+            print iterator;
+            iterator = iterator + 2;
+
+            if (iterator > 50) {
+                break;
+            }
+
+            print "shoud not be printed after 50";
+        }
+    }
+}
+
+print iterator;

tokentype_string.go

@@ -31,28 +31,29 @@ func _() {
 	_ = x[STRING-20]
 	_ = x[NUMBER-21]
 	_ = x[AND-22]
-	_ = x[CLASS-23]
-	_ = x[ENV-24]
-	_ = x[ELSE-25]
-	_ = x[FALSE-26]
-	_ = x[FUN-27]
-	_ = x[FOR-28]
-	_ = x[IF-29]
-	_ = x[NIL-30]
-	_ = x[OR-31]
-	_ = x[PRINT-32]
-	_ = x[RETURN-33]
-	_ = x[SUPER-34]
-	_ = x[THIS-35]
-	_ = x[TRUE-36]
-	_ = x[VAR-37]
-	_ = x[WHILE-38]
-	_ = x[EOF-39]
+	_ = x[BREAK-23]
+	_ = x[CLASS-24]
+	_ = x[ENV-25]
+	_ = x[ELSE-26]
+	_ = x[FALSE-27]
+	_ = x[FUN-28]
+	_ = x[FOR-29]
+	_ = x[IF-30]
+	_ = x[NIL-31]
+	_ = x[OR-32]
+	_ = x[PRINT-33]
+	_ = x[RETURN-34]
+	_ = x[SUPER-35]
+	_ = x[THIS-36]
+	_ = x[TRUE-37]
+	_ = x[VAR-38]
+	_ = x[WHILE-39]
+	_ = x[EOF-40]
 }
 
-const _TokenType_name = "LEFT_PARENRIGHT_PARENLEFT_BRACERIGHT_BRACECOMMADOTMINUSPLUSSEMICOLONSLASHSTARBANGBANG_EQUALEQUALEQUAL_EQUALGREATERGREATER_EQUALLESSLESS_EQUALIDENTIFIERSTRINGNUMBERANDCLASSENVELSEFALSEFUNFORIFNILORPRINTRETURNSUPERTHISTRUEVARWHILEEOF"
+const _TokenType_name = "LEFT_PARENRIGHT_PARENLEFT_BRACERIGHT_BRACECOMMADOTMINUSPLUSSEMICOLONSLASHSTARBANGBANG_EQUALEQUALEQUAL_EQUALGREATERGREATER_EQUALLESSLESS_EQUALIDENTIFIERSTRINGNUMBERANDBREAKCLASSENVELSEFALSEFUNFORIFNILORPRINTRETURNSUPERTHISTRUEVARWHILEEOF"
 
-var _TokenType_index = [...]uint8{0, 10, 21, 31, 42, 47, 50, 55, 59, 68, 73, 77, 81, 91, 96, 107, 114, 127, 131, 141, 151, 157, 163, 166, 171, 174, 178, 183, 186, 189, 191, 194, 196, 201, 207, 212, 216, 220, 223, 228, 231}
+var _TokenType_index = [...]uint8{0, 10, 21, 31, 42, 47, 50, 55, 59, 68, 73, 77, 81, 91, 96, 107, 114, 127, 131, 141, 151, 157, 163, 166, 171, 176, 179, 183, 188, 191, 194, 196, 199, 201, 206, 212, 217, 221, 225, 228, 233, 236}
 
 func (i TokenType) String() string {
 	if i < 0 || i >= TokenType(len(_TokenType_index)-1) {