go-brainfuck-yourself

commit aa565944a634fe5dbfc933226dc8174a94b5766c
parent 95adca93024128834464c55876fda58676697b23
Author: david cochran <about.trout@gmail.com>
Date:   Tue,  7 Jul 2026 20:05:22 -0700

replace recursive eval with for

fixes stack overflow from complex programs, e.g. mandelbrot.

Diffstat:
M
bf.go
 | 
77
+++++++++++++++++++++++++++++++++++++++--------------------------------------

1 file changed, 39 insertions(+), 38 deletions(-)
diff --git a/bf.go b/bf.go
@@ -48,47 +48,48 @@ func (bf *Brainfuck) Eval(cmd byte) error {
 }
 
 func (bf *Brainfuck) eval() error {
-	if n := len(bf.cmds); n == 0 || n <= bf.i {
-		return nil
-	}
-
-	switch bf.cmds[bf.i] {
-	case '>':
-		bf.d++
-		if bf.d >= len(bf.cells) {
-			bf.d -= len(bf.cells)
-		}
-	case '<':
-		bf.d--
-		if bf.d < 0 {
-			bf.d += len(bf.cells)
-		}
-	case '+':
-		bf.cells[bf.d]++
-	case '-':
-		bf.cells[bf.d]--
-	case '.':
-		if _, err := bf.out.Write([]byte{bf.cells[bf.d]}); err != nil {
-			return fmt.Errorf("failed to Write output: %v", err)
-		}
-	case ',':
-		input := make([]byte, 1)
-		if _, err := bf.in.Read(input); err != nil {
-			return fmt.Errorf("failed to Read input: %v", err)
+	for {
+		if n := len(bf.cmds); n == 0 || n <= bf.i {
+			return nil
 		}
-		bf.cells[bf.d] = input[0]
-	case '[':
-		if bf.cells[bf.d] == 0 {
-			bf.i = bf.loops[bf.i]
-		}
-	case ']':
-		if bf.cells[bf.d] != 0 {
-			bf.i = bf.loops[bf.i]
+
+		switch bf.cmds[bf.i] {
+		case '>':
+			bf.d++
+			if bf.d >= len(bf.cells) {
+				bf.d -= len(bf.cells)
+			}
+		case '<':
+			bf.d--
+			if bf.d < 0 {
+				bf.d += len(bf.cells)
+			}
+		case '+':
+			bf.cells[bf.d]++
+		case '-':
+			bf.cells[bf.d]--
+		case '.':
+			if _, err := bf.out.Write([]byte{bf.cells[bf.d]}); err != nil {
+				return fmt.Errorf("failed to Write output: %v", err)
+			}
+		case ',':
+			input := make([]byte, 1)
+			if _, err := bf.in.Read(input); err != nil {
+				return fmt.Errorf("failed to Read input: %v", err)
+			}
+			bf.cells[bf.d] = input[0]
+		case '[':
+			if bf.cells[bf.d] == 0 {
+				bf.i = bf.loops[bf.i]
+			}
+		case ']':
+			if bf.cells[bf.d] != 0 {
+				bf.i = bf.loops[bf.i]
+			}
 		}
-	}
 
-	bf.i++
-	return bf.eval()
+		bf.i++
+	}
 }
 
 // Dump interpreter state to caller.