Permalink
Browse files

Add builtins.string function.

The function 'builtins.split' takes a POSIX extended regular expression
and an arbitrary string. It returns a list of non-matching substring
interleaved by lists of matched groups of the regular expression.

```nix
with builtins;
assert split "(a)b" "abc"      == [ "" [ "a" ] "c" ];
assert split "([ac])" "abc"    == [ "" [ "a" ] "b" [ "c" ] "" ];
assert split "(a)|(c)" "abc"   == [ "" [ "a" null ] "b" [ null "c" ] "" ];
assert split "([[:upper:]]+)" "  FOO   "
                               == [ "  " [ "FOO" ] "   " ];
```
  • Loading branch information...
nbp committed Aug 15, 2017
1 parent f76e85d commit b8867a0239b1930a16f9ef3f7f3e864b01416dff
Showing with 153 additions and 0 deletions.
  1. +37 −0 doc/manual/expressions/builtins.xml
  2. +68 −0 src/libexpr/primops.cc
  3. +48 −0 tests/lang/eval-okay-regex-split.nix
@@ -873,6 +873,43 @@ builtins.sort builtins.lessThan [ 483 249 526 147 42 77 ]
</varlistentry>
<varlistentry><term><function>builtins.split</function>
<replaceable>regex</replaceable> <replaceable>str</replaceable></term>
<listitem><para>Returns a list composed of non matched strings interleaved
with the lists of the <link
xlink:href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04">extended
POSIX regular expression</link> <replaceable>regex</replaceable> matches
of <replaceable>str</replaceable>. Each item in the lists of matched
sequences is a regex group.
<programlisting>
builtins.split "(a)b" "abc"
</programlisting>
Evaluates to <literal>[ "" [ "a" ] "c" ]</literal>.
<programlisting>
builtins.split "([ac])" "abc"
</programlisting>
Evaluates to <literal>[ "" [ "a" ] "b" [ "c" ] "" ]</literal>.
<programlisting>
builtins.split "(a)|(c)" "abc"
</programlisting>
Evaluates to <literal>[ "" [ "a" null ] "b" [ null "c" ] "" ]</literal>.
<programlisting>
builtins.split "([[:upper:]]+)" " FOO "
</programlisting>
Evaluates to <literal>[ " " [ "FOO" ] " " ]</literal>.
</para></listitem>
</varlistentry>
<varlistentry><term><function>builtins.stringLength</function>
<replaceable>e</replaceable></term>
@@ -1745,6 +1745,73 @@ static void prim_match(EvalState & state, const Pos & pos, Value * * args, Value
}
/* Split a string with a regular expression, and return a list of the
non-matching parts interleaved by the lists of the matching groups. */
static void prim_split(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
auto re = state.forceStringNoCtx(*args[0], pos);
try {
std::regex regex(re, std::regex::extended);
PathSet context;
const std::string str = state.forceString(*args[1], context, pos);
auto begin = std::sregex_iterator(str.begin(), str.end(), regex);
auto end = std::sregex_iterator();
// Any matches results are surrounded by non-matching results.
const size_t len = std::distance(begin, end);
state.mkList(v, 2 * len + 1);
size_t idx = 0;
Value * elem;
if (len == 0) {
v.listElems()[idx++] = args[1];
return;
}
for (std::sregex_iterator i = begin; i != end; ++i) {
assert(idx <= 2 * len + 1 - 3);
std::smatch match = *i;
// Add a string for non-matched characters.
elem = v.listElems()[idx++] = state.allocValue();
mkString(*elem, match.prefix().str().c_str());
// Add a list for matched substrings.
const size_t slen = match.size() - 1;
elem = v.listElems()[idx++] = state.allocValue();
// Start at 1, beacause the first match is the whole string.
state.mkList(*elem, slen);
for (size_t si = 0; si < slen; ++si) {
if (!match[si + 1].matched)
mkNull(*(elem->listElems()[si] = state.allocValue()));
else
mkString(*(elem->listElems()[si] = state.allocValue()), match[si + 1].str().c_str());
}
// Add a string for non-matched suffix characters.
if (idx == 2 * len) {
elem = v.listElems()[idx++] = state.allocValue();
mkString(*elem, match.suffix().str().c_str());
}
}
assert(idx == 2 * len + 1);
} catch (std::regex_error &e) {
if (e.code() == std::regex_constants::error_space) {
// limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
throw EvalError("memory limit exceeded by regular expression '%s', at %s", re, pos);
} else {
throw EvalError("invalid regular expression '%s', at %s", re, pos);
}
}
}
static void prim_concatStringSep(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
PathSet context;
@@ -2039,6 +2106,7 @@ void EvalState::createBaseEnv()
addPrimOp("__unsafeDiscardOutputDependency", 1, prim_unsafeDiscardOutputDependency);
addPrimOp("__hashString", 2, prim_hashString);
addPrimOp("__match", 2, prim_match);
addPrimOp("__split", 2, prim_split);
addPrimOp("__concatStringsSep", 2, prim_concatStringSep);
addPrimOp("__replaceStrings", 3, prim_replaceStrings);
@@ -0,0 +1,48 @@
with builtins;
# Non capturing regex returns empty lists
assert split "foobar" "foobar" == ["" [] ""];
assert split "fo*" "f" == ["" [] ""];
assert split "fo+" "f" == ["f"];
assert split "fo*" "fo" == ["" [] ""];
assert split "fo*" "foo" == ["" [] ""];
assert split "fo+" "foo" == ["" [] ""];
assert split "fo{1,2}" "foo" == ["" [] ""];
assert split "fo{1,2}" "fooo" == ["" [] "o"];
assert split "fo*" "foobar" == ["" [] "bar"];
# Capturing regex returns a list of sub-matches
assert split "(fo*)" "f" == ["" ["f"] ""];
assert split "(fo+)" "f" == ["f"];
assert split "(fo*)" "fo" == ["" ["fo"] ""];
assert split "(f)(o*)" "f" == ["" ["f" ""] ""];
assert split "(f)(o*)" "foo" == ["" ["f" "oo"] ""];
assert split "(fo+)" "foo" == ["" ["foo"] ""];
assert split "(fo{1,2})" "foo" == ["" ["foo"] ""];
assert split "(fo{1,2})" "fooo" == ["" ["foo"] "o"];
assert split "(fo*)" "foobar" == ["" ["foo"] "bar"];
# Matches are greedy.
assert split "(o+)" "oooofoooo" == ["" ["oooo"] "f" ["oooo"] ""];
# Matches multiple times.
assert split "(b)" "foobarbaz" == ["foo" ["b"] "ar" ["b"] "az"];
# Split large strings containing newlines. null are inserted when a
# pattern within the current did not match anything.
assert split "[[:space:]]+|([',.!?])" ''
Nix Rocks!
That's why I use it.
'' == [
"Nix" [ null ] "Rocks" ["!"] "" [ null ]
"That" ["'"] "s" [ null ] "why" [ null ] "I" [ null ] "use" [ null ] "it" ["."] "" [ null ]
""
];
# Documentation examples
assert split "(a)b" "abc" == [ "" [ "a" ] "c" ];
assert split "([ac])" "abc" == [ "" [ "a" ] "b" [ "c" ] "" ];
assert split "(a)|(c)" "abc" == [ "" [ "a" null ] "b" [ null "c" ] "" ];
assert split "([[:upper:]]+)" " FOO " == [ " " [ "FOO" ] " " ];
true

0 comments on commit b8867a0

Please sign in to comment.