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examples: add regex_with_memoization.v (#6355)

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Ruofan XU 2020-09-12 14:51:30 +08:00 committed by GitHub
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import os
fn regex_match(src, pat string) bool {
src_size := src.len + 1
pat_size := pat.len + 1
mut memo := [][]int{len: src_size, init: []int{len: pat_size, init: -1}}
return regex_match_core(src, pat, 0, 0, mut memo)
}
fn regex_match_core(src, pat string, src_pos, pat_pos int, mut memo [][]int) bool {
if memo[src_pos][pat_pos] != -1 {
return memo[src_pos][pat_pos] == 1
}
mut spos := src_pos
mut ppos := pat_pos
if spos >= src.len && ppos >= pat.len {
memo[src_pos][pat_pos] = 1
return true
} else if spos < src.len && ppos >= pat.len {
memo[src_pos][pat_pos] = 0
return false
} else if spos >= src.len && ppos < pat.len {
if pat[ppos] == `\\` {
ppos++
}
res := ppos + 1 < pat.len &&
pat[ppos + 1] in [`*`, `?`] && regex_match_core(src, pat, spos, ppos + 2, mut memo)
memo[src_pos][pat_pos] = if res { 1 } else { 0 }
return res
} else {
first_is_bslash := pat[ppos] == `\\`
if first_is_bslash {
ppos++
}
first_bslash_and_match := first_is_bslash && ppos < pat.len &&
(((pat[ppos] == `d` && src[spos].is_digit()) ||
(pat[ppos] == `D` && !src[spos].is_digit()) ||
(pat[ppos] == `s` && src[spos].is_space()) ||
(pat[ppos] == `S` && !src[spos].is_space()) ||
(pat[ppos] == `w` && (src[spos].is_digit() || src[spos].is_letter() || src[spos] == `_`)) ||
(pat[ppos] == `W` && !(src[spos].is_digit() || src[spos].is_letter() || src[spos] == `_`))) ||
(pat[ppos] in [`d`, `D`, `s`, `S`, `w`, `W`] &&
ppos + 1 < pat.len && pat[ppos + 1] in [`*`, `?`, `+`]) ||
(pat[ppos] !in [`d`, `D`, `s`, `S`, `w`, `W`] && src[spos] == pat[ppos]))
if ppos + 1 < pat.len {
match pat[ppos + 1] {
`*` {
if first_bslash_and_match {
res := regex_match_core(src, pat, spos + 1, ppos - 1, mut memo) || regex_match_core(src, pat, spos, ppos +
2, mut memo)
memo[src_pos][pat_pos] = if res { 1 } else { 0 }
return res
} else if src[spos] == pat[ppos] || pat[ppos] == `.` {
res := regex_match_core(src, pat, spos + 1, ppos, mut memo) || regex_match_core(src, pat, spos, ppos +
2, mut memo)
memo[src_pos][pat_pos] = if res { 1 } else { 0 }
return res
} else {
res := regex_match_core(src, pat, spos, ppos + 2, mut memo)
memo[src_pos][pat_pos] = if res { 1 } else { 0 }
return res
}
}
`+` {
if first_bslash_and_match {
res := regex_match_core(src, pat, spos + 1, ppos - 1, mut memo) || regex_match_core(src, pat, spos +
1, ppos + 2, mut memo)
memo[src_pos][pat_pos] = if res { 1 } else { 0 }
return res
} else if src[spos] == pat[ppos] || pat[ppos] == `.` {
res := regex_match_core(src, pat, spos + 1, ppos, mut memo) || regex_match_core(src, pat, spos +
1, ppos + 2, mut memo)
memo[src_pos][pat_pos] = if res { 1 } else { 0 }
return res
} else {
memo[src_pos][pat_pos] = 0
return false
}
}
`?` {
if first_bslash_and_match || src[spos] == pat[ppos] || pat[ppos] == `.` {
res := regex_match_core(src, pat, spos + 1, ppos + 2, mut memo) || regex_match_core(src, pat, spos, ppos +
2, mut memo)
memo[src_pos][pat_pos] = if res { 1 } else { 0 }
return res
} else {
res := regex_match_core(src, pat, spos, ppos + 2, mut memo)
memo[src_pos][pat_pos] = if res { 1 } else { 0 }
return res
}
}
else {}
}
}
if first_is_bslash {
res := first_bslash_and_match && regex_match_core(src, pat, spos + 1, ppos + 1, mut memo)
memo[src_pos][pat_pos] = if res { 1 } else { 0 }
return res
} else {
res := (src[spos] == pat[ppos] ||
pat[ppos] == `.`) &&
pat[ppos] != `\\` && regex_match_core(src, pat, spos + 1, ppos + 1, mut memo)
memo[src_pos][pat_pos] = if res { 1 } else { 0 }
return res
}
}
}
fn main() {
mut cnt := 0
println('currently supported patterns: . ? + * \\ \\d \\D \\s \\S \\w \\W')
println('example: source `address@domain.net` matches pattern `\\w+@domain\\.net`')
println('enter `exit` to quit\n')
for {
cnt++
src := os.input('[$cnt] enter source string: ')
if src == 'exit' {
break
}
pat := os.input('[$cnt] enter pattern string: ')
if pat == 'exit' {
break
}
println('[$cnt] whether `$src` matches `$pat`: ${regex_match(src,pat)}')
}
}