go-brainfuck-yourself

commit 9f20ae3252a41835203ebd2ff83f1aac4d4f86ea
parent ed31b64ea0479f9fcf59a55b7e404998f238352d
Author: david cochran <about.trout@gmail.com>
Date:   Thu, 23 Jul 2026 20:39:38 -0700

remove unnecessary slice allocation from . and ,

we can Read from and Write to bf.cells directly -- no need to allocate
a 1-byte slice every time. the benchmark win here is seen in allocs/op.

```
$ go test -bench=. -benchmem
goos: darwin
goarch: arm64
pkg: github.com/abtrout/gbfy
cpu: Apple M3
BenchmarkLong-8                        1        10477888417 ns/op          37896 B/op         23 allocs/op
BenchmarkMandelbrot-8                  1        12086849000 ns/op         329912 B/op         39 allocs/op
BenchmarkFactor-8                      1        1320697583 ns/op          128120 B/op         30 allocs/op
PASS
ok      github.com/abtrout/gbfy 24.177s
```

Diffstat:
M
bf.go
 | 
10
++++++----

1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/bf.go b/bf.go
@@ -66,15 +66,17 @@ func (bf *Brainfuck) eval() error {
 		case '-':
 			bf.cells[bf.d]--
 		case '.':
-			if _, err := bf.out.Write([]byte{bf.cells[bf.d]}); err != nil {
+			if n, err := bf.out.Write(bf.cells[bf.d : bf.d+1]); n == 0 {
+				return fmt.Errorf("failed to Write ouput: no bytes written")
+			} else if err != nil {
 				return fmt.Errorf("failed to Write output: %v", err)
 			}
 		case ',':
-			input := make([]byte, 1)
-			if _, err := bf.in.Read(input); err != nil {
+			if n, err := bf.in.Read(bf.cells[bf.d : bf.d+1]); n == 0 {
+				return fmt.Errorf("failed to Read input: no bytes read")
+			} else if 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]