Paren Debug Skill
When to Use
Invoke this skill when you encounter:
- •
Exception in read: unexpected end-of-file reading list at line N - •
Exception in read: unexpected close parenthesis at line N - •Any situation where you're manually counting parentheses
- •After editing Scheme code and getting parse errors
Tools Available
paren-locate - Primary Tool (Stack-Based)
The most useful tool. Shows exact locations of paren errors:
bash
scheme -q <<'EOF' (load "boundary/tools/paren-check.ss") (paren-locate "path/to/file.ss") EOF
Output format is compiler-friendly (file:line:col):
code
path/to/file.ss:46:1: error: unclosed '(' - never closed
path/to/file.ss:61:19: error: mismatched brackets: opened '[' at line 61 col 12, closed with ')'
paren-ok? - Quick Check
Returns #t if file is balanced, #f otherwise:
bash
scheme -q <<'EOF' (load "boundary/tools/paren-check.ss") (paren-ok? "path/to/file.ss") EOF
paren-errors - Programmatic Access
Returns list of error structs for further processing:
bash
scheme -q <<'EOF' (load "boundary/tools/paren-check.ss") (paren-errors "path/to/file.ss") EOF
paren-check - Legacy Balance Report
Line-by-line balance report (less precise but shows running totals):
bash
scheme -q <<'EOF' (load "boundary/tools/paren-check.ss") (paren-check "path/to/file.ss") EOF
./fold -c / ./fold --check-syntax - Quick CLI Check
Fast paren check from command line (no daemon needed):
bash
./fold -c path/to/file.ss ./fold --check-syntax path/to/file.ss
Output:
code
# Success:
path/to/file.ss: ✓ All parentheses balanced
# Error:
path/to/file.ss:46:1: error: unclosed '(' - never closed
Exit codes: 0 = balanced, 1 = errors found.
Workflow
- •When you see a paren error: Run
paren-locatefirst - •Read the error location: The output tells you exactly which opener was never closed
- •Fix at the source: Go to the reported line/column and add the missing closer
- •Verify: Run
paren-ok?to confirm the fix
Example Session
bash
# 1. You edited exports.ss and get:
# Exception in read: unexpected end-of-file reading list at line 46
# 2. Run paren-locate
scheme -q <<'EOF'
(load "boundary/tools/paren-check.ss")
(paren-locate "boundary/introspect/exports.ss")
EOF
# Output:
# boundary/introspect/exports.ss:46:1: error: unclosed '(' - never closed
# 3. The error is at line 46, column 1 - that's where the unclosed ( is!
# NOT at the end of the file where Scheme complained.
# 4. Fix and verify:
scheme -q <<'EOF'
(load "boundary/tools/paren-check.ss")
(paren-ok? "boundary/introspect/exports.ss")
EOF
# Output: #t
Error Types Detected
| Type | Message Pattern | Meaning |
|---|---|---|
unclosed | unclosed '(' - never closed | Opener at this location has no matching closer |
extra-close | unexpected ')' - no matching opener | Closer with no corresponding opener |
mismatch | opened '[' at line X, closed with ')' | Wrong bracket type used to close |
Tips
- •Don't count parens manually - always use
paren-locate - •The error location is where to fix - unlike Scheme's error which points to where the list started
- •Check after every significant edit - catch errors early
- •Mismatch detection - the tool catches
(foo]style errors that pure counting misses
File Location
boundary/tools/paren-check.ss - Load this to access all paren-checking functions.