metamath · vince-gonzalez · Aug 23, 2026 · Aug 24, 2026 · Aug 24, 2026 · Sep 8, 2026
diff --git a/scripts/README.md b/scripts/README.md
@@ -3,3 +3,6 @@ This directory contains various scripts to work with metamath files.
 Most are shell scripts (on Windows you can run them via Cygwin).
 
 Most assume that the "metamath" executable is available.
+
+"rewrap-comments.py" does not.  It rewraps comments in Python, which is
+enough when a change touches comments and not proofs.
diff --git a/scripts/rewrap-comments.py b/scripts/rewrap-comments.py
@@ -0,0 +1,277 @@
+#!/usr/bin/env python3
+# Rewrap Metamath comments without the metamath C program.
+# Vincent Gonzalez <vincegonzalez@me.com>
+# SPDX-License-Identifier: CC0-1.0
+#
+# scripts/rewrap runs "write source /rewrap" through the metamath executable,
+# which also runs "save proof */compressed/fast" and reindents proof bodies.
+# This does only the comment filling, so it is enough when a change touches
+# comments and not proofs.  Change a proof and you still need the executable.
+#
+#   rewrap-comments.py set.mm --check      report comments that need rewrapping
+#   rewrap-comments.py set.mm --in-place   rewrap them
+#
+# Comments it does not model are left untouched and their labels printed: those
+# containing <HTML>, those not attached to a $a or $p, and those holding a run
+# too long to break (a ~ reference followed by a long URL).
+#
+# It also differs from the metamath executable in one respect: file inclusions
+# are not resolved.  The executable parses after resolving them; this reads a
+# single file, so a comment in an included file is checked only if the tool is
+# run on that file as well.  No database in this repository uses inclusions.
+#
+# The rules below are transcribed from rewrapComment() in mmpars.c and the
+# line-breaking loop of printLongLine() in mminou.c.
+
+import argparse
+import re
+import sys
+
+WIDTH = 79
+NB = "\x04"  # ASCII_4 in mmpars.c: a space the line may not break at
+
+OPENING = "(['\""
+CLOSING = ".,;)?!:]'\""
+SENTENCE_END = ")'\""
+
+PROOF_DISCOURAGED = "(Proof modification is discouraged.)"
+USAGE_DISCOURAGED = "(New usage is discouraged.)"
+
+COMMENT = re.compile(r"\$\(.*?\$\)", re.S)
+# A file inclusion may sit between a comment and the statement it describes.
+# The metamath executable resolves inclusions before parsing, so step over
+# them here rather than reading "$[" as a label.
+STATEMENT = re.compile(r"(?:\s*\$\[.*?\$\])*\s*[A-Za-z0-9_.\-]+\s+\$[ap]\s",
+                       re.S)
+
+
+def space_surround(s, ch, subscript_exception=False):
+    # A closing backtick followed by _ or - takes no space: ` a `_2 renders as a
+    # subscript and ` a ` _2 does not.  mmpars.c carries the same exception.
+    out = list(s)
+    i = 1
+    mathmode = 0
+    while i < len(out) - 1:
+        if out[i] != ch:
+            i += 1
+            continue
+        if out[i - 1] == ch or (i + 1 < len(out) and out[i + 1] == ch):
+            i += 2  # `` or ~~ escape
+            continue
+        mathmode = 1 - mathmode
+        nxt = out[i + 1] if i + 1 < len(out) else ""
+        if nxt not in (" ", "\n", ""):
+            if not subscript_exception or mathmode == 1 or nxt not in ("_", "-"):
+                out.insert(i + 1, " ")
+        if out[i - 1] != " ":
+            out.insert(i, " ")
+            i += 1
+        i += 1
+    return "".join(out)
+
+
+def two_spaces_after_sentences(c):
+    # Only when the next character is a capital or opening punctuation, and not
+    # after an initial.  This is why "[Margaris] p. 49" keeps one space.
+    for ch in ".?!:":
+        i = 1
+        while True:
+            p = c.find(ch, i)
+            if p < 0:
+                break
+            i = p + 1
+            if ch == "." and p > 0 and "A" <= c[p - 1] <= "Z":
+                continue
+            q = p + 1
+            if q < len(c) and c[q] in SENTENCE_END:
+                q += 1
+            if q >= len(c) or c[q] != " ":
+                continue
+            nxt = c[q + 1] if q + 1 < len(c) else ""
+            if ("A" <= nxt <= "Z") or (nxt and nxt in OPENING):
+                c = c[:q + 1] + " " + c[q + 1:]
+                i = q + 2
+    return c
+
+
+def mark_nonbreaking(c):
+    n = len(c)
+    tmpl = [" "] * n
+    for p in range(2, n - 2):
+        if c[p] != " ":
+            continue
+        if c[p - 1] == "~" and c[p - 2] != "~":
+            tmpl[p] = NB  # do not split "~ label"
+        elif (c[p - 2] == " " or c[p - 2] in OPENING) and c[p - 1] in OPENING:
+            tmpl[p] = NB
+        elif (p + 2 < n
+              and (c[p + 2] in (" ", "\n", NB) or c[p + 2] in CLOSING)
+              and c[p + 1] in CLOSING):
+            tmpl[p] = NB
+        elif c[p - 3] == " " and c[p - 2] == "p" and c[p - 1] == ".":
+            tmpl[p] = NB  # do not split " p. 49"
+    if n >= 3:
+        tmpl[n - 3] = NB  # the space before "$)"
+    return "".join(NB if tmpl[p] == NB else c[p] for p in range(n))
+
+
+def normalize(comment):
+    c = space_surround(comment, "`", subscript_exception=True)
+    if "`" not in c[1:]:
+        c = space_surround(c, "~")
+
+    # A single newline becomes a space; a doubled one is a paragraph break.
+    body = list(c)
+    for p in range(2, len(body) - 2):
+        if body[p] == "\n" and body[p - 1] != "\n" and body[p + 1] != "\n":
+            body[p] = " "
+    c = re.sub(r"  +", " ", "".join(body))
+
+    while len(c) >= 4 and c[-4] in (" ", "\n"):
+        c = c[:-4] + c[-2:]
+    if len(c) >= 4 and c[-4].islower():
+        c = c[:-3] + ". $)"
+
+    out = []
+    math = False
+    for p, ch in enumerate(c):
+        if ch == "`":
+            math = not math
+        out.append(NB if (math and ch == " " and 2 <= p < len(c) - 2) else ch)
+    c = "".join(out)
+
+    for markup in (PROOF_DISCOURAGED, USAGE_DISCOURAGED):
+        p = c.find(markup)
+        if p >= 0:
+            c = c[:p] + markup.replace(" ", NB) + c[p + len(markup):]
+
+    return mark_nonbreaking(two_spaces_after_sentences(c))
+
+
+def fill(text, first_prefix, cont_prefix, width=WIDTH):
+    # printLongLine() scans back from one past the margin for a space to break
+    # at.  When there is none it widens the margin rather than splitting a
+    # token, which is how long URLs stay intact.
+    lines = []
+    line = first_prefix + text
+    first = True
+    while len(line) > width:
+        p = width
+        while p > 0 and line[p] != " ":
+            p -= 1
+        if p <= len(first_prefix if first else cont_prefix):
+            q = line.find(" ", width)
+            if q < 0:
+                break
+            p = q
+        lines.append(line[:p].rstrip(" " + NB))
+        line = cont_prefix + line[p + 1:].lstrip()
+        first = False
+    lines.append(line.rstrip(" " + NB))
+    return lines
+
+
+def rewrap_comment(block, indent, width=WIDTH):
+    """Rewrap one $( ... $) comment whose $( sits at column indent."""
+    if not (block.startswith("$(") and block.endswith("$)")):
+        raise ValueError("not a comment")
+    c = normalize(block)
+    pad = " " * indent
+    out = []
+    for k, para in enumerate(c.split("\n\n")):
+        # mmpars.c strips the leading spaces after each newline before adding
+        # indent + 3; keeping them puts every later paragraph a column deep.
+        body = para.strip("\n").lstrip(" ")
+        out.append("\n".join(fill(body, pad if k == 0 else pad + "   ",
+                                  pad + "   ", width)))
+    return "\n\n".join(out).replace(NB, " ")
+
+
+def modelled(block, indent, following, width=WIDTH):
+    """Whether this reproduces rewrap for this comment.  If not, leave it be."""
+    if "<HTML>" in block:
+        return False
+    if not STATEMENT.match(following):
+        # The rewrapping in outputStatement() sits inside the $a/$p case, so
+        # a comment not attached to a statement is never reflowed by the
+        # metamath executable.
+        return False
+    budget = width - indent - 3
+    for run in normalize(block).split(" "):
+        if len(run.replace(NB, " ").strip()) > budget:
+            return False
+    return True
+
+
+def process(text):
+    """Returns the rewrapped text, the labels changed, and the labels skipped."""
+    out = []
+    pos = 0
+    changed = []
+    skipped = []
+    for m in COMMENT.finditer(text):
+        out.append(text[pos:m.start()])
+        start = text.rfind("\n", 0, m.start()) + 1
+        prefix = text[start:m.start()]
+        block = m.group(0)
+        following = text[m.end():m.end() + 160]
+        label = STATEMENT.match(following)
+        label = following.split()[0] if label else "?"
+        if prefix.strip() or not modelled(block, len(prefix), following):
+            out.append(block)
+            if not prefix.strip() and STATEMENT.match(following):
+                skipped.append(label)
+        else:
+            new = rewrap_comment(block, len(prefix))[len(prefix):]
+            out.append(new)
+            if new != block:
+                changed.append(label)
+        pos = m.end()
+    out.append(text[pos:])
+    return "".join(out), changed, skipped
+
+
+def main():
+    ap = argparse.ArgumentParser(
+        description="Rewrap Metamath comments without the metamath "
+                    "executable.")
+    ap.add_argument("database")
+    ap.add_argument("--check", action="store_true",
+                    help="exit 1 if any comment needs rewrapping")
+    ap.add_argument("--in-place", action="store_true",
+                    help="write the database back")
+    ap.add_argument("--verbose", action="store_true",
+                    help="name the comments left alone even when none changed")
+    args = ap.parse_args()
+
+    with open(args.database, encoding="utf-8", errors="replace") as f:
+        text = f.read()
+    result, changed, skipped = process(text)
+
+    # Name the ones left alone only when there is something to act on;
+    # a passing check should be quiet.
+    if skipped and (changed or args.verbose):
+        print("left alone (%d): %s" %
+              (len(skipped), ", ".join(skipped[:12])
+               + ("..." if len(skipped) > 12 else "")), file=sys.stderr)
+
+    if args.check:
+        if changed:
+            print("%d comment(s) need rewrapping: %s" %
+                  (len(changed), ", ".join(changed[:12])
+                   + ("..." if len(changed) > 12 else "")))
+            return 1
+        print("rewrapped already; %d comment(s) not modelled" % len(skipped))
+        return 0
+
+    if args.in_place:
+        with open(args.database, "w", encoding="utf-8", newline="\n") as f:
+            f.write(result)
+        print("rewrapped %d comment(s)" % len(changed))
+    else:
+        sys.stdout.write(result)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())