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