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function dbg(x)
{
printf("dbg: <%s>\n", x)
return x
}
function empty(s)
{
return s == ""
}
function eat_char(s)
{
return substr(s, 2)
}
function eat_chars(s, n)
{
return substr(s, n + 1)
}
function matches(s, pfx)
{
return substr(s, 1, length(pfx)) == pfx
}
function match_and_eat(s, pfx)
{
if (matches(s, pfx))
return eat_chars(s, length(pfx))
return s
}
function match_and_eat_else(s, pfx, e)
{
if (matches(s, pfx))
return eat_chars(s, length(pfx))
return e
}
function eat_rchar(c)
{
if (c ~ /^\\./)
return eat_chars(c, 2)
if (c == "$")
return c
if (c !~ /^[\[\*\+\?{}\(\)|]/)
return eat_char(c)
return c
}
function eat_bchar(c)
{
if (c ~ /^\\]|\\-|\\\\/)
return eat_chars(c, 2)
if (c !~ /^[\-\[]/)
return eat_char(c)
return c
}
function eat_class(c)
{
c = match_and_eat(c, "[:alnum:]")
c = match_and_eat(c, "[:alpha:]")
c = match_and_eat(c, "[:blank:]")
c = match_and_eat(c, "[:cntrl:]")
c = match_and_eat(c, "[:digit:]")
c = match_and_eat(c, "[:graph:]")
c = match_and_eat(c, "[:lower:]")
c = match_and_eat(c, "[:print:]")
c = match_and_eat(c, "[:punct:]")
c = match_and_eat(c, "[:space:]")
c = match_and_eat(c, "[:upper:]")
return match_and_eat(c, "[:xdigit:]")
}
function eat_bracket_exp(e,
#local
f, o)
{
o = e
e = eat_char(e)
for (;;) {
if (matches(e, "]")) {
return eat_char(e)
}
if (matches(e, "[")) {
f = eat_class(e)
if (f == e)
return o
e = f
continue;
}
f = eat_bchar(e)
if (f == e)
return o
e = f
if (matches(e, "-")) {
e = eat_char(e)
f = eat_bchar(e)
if (f == e)
return o
e = f
}
}
}
function eat_rep_notation(n,
# local
o)
{
o = n
n = eat_char(n)
if (n !~ /^[0-9]/)
return o
while (n ~ /^[0-9]/)
n = eat_char(n)
if (matches(n, "}"))
return eat_char(n)
if (!matches(n, ","))
return o
n = eat_char(n)
if (matches(n, "}"))
return eat_char(n)
if (n !~ /^[0-9]/)
return o
while (n ~ /^[0-9]/)
n = eat_char(n)
return match_and_eat_else(n, "}", o)
}
function eat_factor(f)
{
if (matches(f, "("))
return match_and_eat_else(eat_regex(eat_char(f)), ")", f)
if (matches(f, "["))
return eat_bracket_exp(f)
return eat_rchar(f)
}
function eat_term(t,
#local
s)
{
s = eat_factor(t)
if (empty(s) || s == t)
return s
t = s
if (t ~ /^[?+*]/)
return eat_char(t)
if (matches(t, "{"))
return eat_rep_notation(t)
return t
}
function eat_regex(r,
#locals
s)
{
if (empty(r))
return r
s = eat_term(r)
if (empty(s) || s == r)
return s
r = s;
if (matches(r, "|"))
r = eat_char(r)
return eat_regex(r)
}
function regex_check(r)
{
if (matches(r, "^"))
r = eat_char(r)
if (empty(r))
return r
r = eat_regex(r)
if (r == "$")
r = ""
return r
}
function is_regex(r)
{
return empty(regex_check(r))
}
{
ok = is_regex($0)
printf("is_regex(\"%s\") = %d", $0, ir)
if (!ok)
printf(", junk = \"%s\"", regex_check($0))
printf("\n")
}
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