This post is very low quality for comedic effect.

A detailed list of instructions

Take one nix, apply this patch^[1]:

What does this do? It adds a new token $ to the nix languages parser and exposes it as __dollar, essentially by copying the way this works for __lessThan.

Hack on your nix:

nix develop
./bootstrap.sh
./configure $configureFlags --prefix=$(pwd)/outputs/out
make -j $NIX_BUILD_CORES
outputs/out/bin/nix repl

Now in the nix repl that just opened:

nix-repl> __dollar = x: y: builtins.foldl' (a: b: a b) x y

This makes $ an infix operator that’s essentially just a generic apply.

Now just create a toy example to demonstrate:

nix-repl> concat = x: y: z: (x + y + z)
nix-repl> concat $ ["literally" " " "dollar sign"]

And your repl will say:

"literally dollar sign"

Tadaa! That’s all it takes to add the $ operator to nix, just like Haskell.

The end $\text{\(^ヮ^)/}$

1. diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
   index 201370b90..4b26af623 100644
   --- a/src/libexpr/parser.y
   +++ b/src/libexpr/parser.y
   @@ -353,6 +353,7 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, ParseData * data, const char * err
    %left AND
    %nonassoc EQ NEQ
    %nonassoc '<' '>' LEQ GEQ
   +%nonassoc '$' DOL
    %right UPDATE
    %left NOT
    %left '+' '-'
   @@ -411,6 +412,8 @@ expr_op
      | expr_op LEQ expr_op { $$ = new ExprOpNot(new ExprCall(makeCurPos(@2, data), new ExprVar(data->symbols.create("__lessThan")), {$3, $1})); }
      | expr_op '>' expr_op { $$ = new ExprCall(makeCurPos(@2, data), new ExprVar(data->symbols.create("__lessThan")), {$3, $1}); }
      | expr_op GEQ expr_op { $$ = new ExprOpNot(new ExprCall(makeCurPos(@2, data), new ExprVar(data->symbols.create("__lessThan")), {$1, $3})); }
   +  | expr_op '$' expr_op { $$ = new ExprCall(makeCurPos(@2, data), new ExprVar(data->symbols.create("__dollar")), {$1, $3}); }
   +  | expr_op DOL expr_op { $$ = new ExprOpNot(new ExprCall(makeCurPos(@2, data), new ExprVar(data->symbols.create("__dollar")), {$3, $1})); }
      | expr_op AND expr_op { $$ = new ExprOpAnd(makeCurPos(@2, data), $1, $3); }
      | expr_op OR expr_op { $$ = new ExprOpOr(makeCurPos(@2, data), $1, $3); }
      | expr_op IMPL expr_op { $$ = new ExprOpImpl(makeCurPos(@2, data), $1, $3); }
   diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
   index ddf529b9e..00622a142 100644
   --- a/src/libexpr/primops.cc
   +++ b/src/libexpr/primops.cc
   @@ -3583,6 +3583,24 @@ static RegisterPrimOp primop_lessThan({
        .fun = prim_lessThan,
    });
   
   +static void prim_dollar(EvalState & state, const PosIdx pos, Value * * args, Value & v)
   +{
   +    state.forceValue(*args[0], pos);
   +    state.forceValue(*args[1], pos);
   +    // pos is exact here, no need for a message.
   +    CompareValues comp(state, noPos, "");
   +    v.mkBool(comp(args[0], args[1]));
   +}
   +
   +static RegisterPrimOp primop_dollar({
   +    .name = "__dollar",
   +    .args = {"e1", "e2"},
   +    .doc = R"(
   +      Just like haskell :)
   +    )",
   +    .fun = prim_dollar,
   +});
   +
   
    /*************************************************************
     * String manipulation
   

   ↩