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Add replaceStrings primop

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This is a generalisation of replaceChars in Nixpkgs.
This commit is contained in:
Eelco Dolstra 2015-07-24 15:32:24 +02:00
parent 2e8fd4c5cd
commit d6d5885c15
4 changed files with 63 additions and 1 deletions
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17
doc/manual/expressions/builtins.xml
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@ -733,6 +733,23 @@ removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</programlisting>
</varlistentry>
<varlistentry><term><function>builtins.replaceStrings</function>
<replaceable>from</replaceable> <replaceable>to</replaceable> <replaceable>s</replaceable></term>
<listitem><para>Given string <replaceable>s</replaceable>, replace
every occurrence of the strings in <replaceable>from</replaceable>
with the corresponding string in
<replaceable>to</replaceable>. For example,
<programlisting>
builtins.replaceStrings ["oo" "a"] ["a" "i"] "foobar"
</programlisting>
evaluates to <literal>"fabir"</literal>.</para></listitem>
</varlistentry>
<varlistentry><term><function>builtins.seq</function>
<replaceable>e1</replaceable> <replaceable>e2</replaceable></term>

38
src/libexpr/primops.cc
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@ -1519,7 +1519,7 @@ static void prim_concatStringSep(EvalState & state, const Pos & pos, Value * * a
PathSet context;
auto sep = state.forceString(*args[0], context, pos);
state.forceList(*args[1]);
state.forceList(*args[1], pos);
string res;
res.reserve((args[1]->listSize() + 32) * sep.size());
@ -1534,6 +1534,41 @@ static void prim_concatStringSep(EvalState & state, const Pos & pos, Value * * a
}
static void prim_replaceStrings(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
state.forceList(*args[0], pos);
state.forceList(*args[1], pos);
if (args[0]->listSize() != args[1]->listSize())
throw EvalError(format("‘from’ and ‘to’ arguments to ‘replaceStrings’ have different lengths, at %1%") % pos);
Strings from;
for (unsigned int n = 0; n < args[0]->listSize(); ++n)
from.push_back(state.forceStringNoCtx(*args[0]->listElems()[n], pos));
Strings to;
for (unsigned int n = 0; n < args[1]->listSize(); ++n)
to.push_back(state.forceStringNoCtx(*args[1]->listElems()[n], pos));
PathSet context;
auto s = state.forceString(*args[2], context, pos);
string res;
for (size_t p = 0; p < s.size(); ) {
bool found = false;
for (auto i = from.begin(), j = to.begin(); i != from.end(); ++i, ++j)
if (s.compare(p, i->size(), *i) == 0) {
found = true;
p += i->size();
res += *j;
break;
}
if (!found) res += s[p++];
}
mkString(v, res, context);
}
/*************************************************************
* Versions
*************************************************************/
@ -1741,6 +1776,7 @@ void EvalState::createBaseEnv()
addPrimOp("__hashString", 2, prim_hashString);
addPrimOp("__match", 2, prim_match);
addPrimOp("__concatStringsSep", 2, prim_concatStringSep);
addPrimOp("__replaceStrings", 3, prim_replaceStrings);
// Versions
addPrimOp("__parseDrvName", 1, prim_parseDrvName);

1
tests/lang/eval-okay-replacestrings.exp Normal file
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@ -0,0 +1 @@
[ "faabar" "fbar" "fubar" "faboor" "fubar" ]

8
tests/lang/eval-okay-replacestrings.nix Normal file
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@ -0,0 +1,8 @@
with builtins;
[ (replaceStrings ["o"] ["a"] "foobar")
(replaceStrings ["o"] [""] "foobar")
(replaceStrings ["oo"] ["u"] "foobar")
(replaceStrings ["oo" "a"] ["a" "oo"] "foobar")
(replaceStrings ["oo" "oo"] ["u" "i"] "foobar")
]