fix: -f format-flag consistency across implementations

- Zig rejected -f=NxM (only the other four accepted the '=' form); now strips
  an optional leading '=' in the short-flag handler.
- Node rejected bare -f and consumed the next arg as the spec; now bare -f means
  default 8x10 grouping (matching Zig/Lua/C) and does not eat the input filename.
New cross-impl test #5e (bare -f and -f=NxM both succeed).

Author: pmarreck

bin/printable-binary-node.js

@@ -172,11 +172,9 @@ function parseArgs(argv) {
     } else if (arg === '-s' || arg === '--spaces') {
       spacesMode = true;
     } else if (arg === '-f' || arg === '--format') {
-      if (i + 1 >= argv.length) {
-        process.stderr.write('Error: --format requires a value like 75x1\n');
-        process.exit(1);
-      }
-      formatSpec = argv[++i];
+      // Bare -f: default grouping (8x10), like the other implementations. Do not
+      // consume the next argument (it is the input file); use -f=NxM for a spec.
+      formatSpec = '8x10';
     } else if (arg.startsWith('-f=')) {
       formatSpec = arg.slice(3);
     } else if (arg.startsWith('--format=')) {

src/zig/main.zig

@@ -313,7 +313,10 @@ fn parseArgs(allocator: std.mem.Allocator, args: []const []const u8) !Options {
                     'h' => opts.help_mode = true,
                     'f' => {
                         if (j + 1 < arg.len) {
-                            const parsed = parseFormatSpec(arg[j + 1 ..]) catch return error.InvalidFormat;
+                            // Accept both -f8x10 and -f=8x10 (strip an optional '=').
+                            const spec = arg[j + 1 ..];
+                            const spec_trimmed = if (spec.len > 0 and spec[0] == '=') spec[1..] else spec;
+                            const parsed = parseFormatSpec(spec_trimmed) catch return error.InvalidFormat;
                             opts.format_mode = true;
                             opts.format_group = parsed.group;
                             opts.format_groups_per_line = parsed.per_line;

test/test

@@ -264,6 +264,17 @@ else
     exit 1
 fi
 
+# Test 5e: -f (bare, default grouping) and -f=NxM (attached spec) consistency
+echo -e "${BLUE}Test #5e: -f / -f=NxM format-flag consistency${NC}"
+rc1=0; printf 'AAAABBBB' | $SCRIPT -f >/dev/null 2>&1 || rc1=$?
+rc2=0; printf 'AAAABBBB' | $SCRIPT -f=2x2 >/dev/null 2>&1 || rc2=$?
+if [[ $rc1 -eq 0 && $rc2 -eq 0 ]]; then
+    echo -e "${GREEN}PASS${NC}"
+else
+    echo -e "${RED}FAIL${NC} (bare -f exit=$rc1, -f=2x2 exit=$rc2)"
+    exit 1
+fi
+
 # Test 6: Piped input
 echo -e "${BLUE}Test #6: Piped input${NC}"
 RESULT=$(echo -n "Test" | $SCRIPT | $SCRIPT -d)