Implement ~ with many arguments

CORE.setting

@@ -223,11 +223,17 @@ my class Bool is Enum {
 constant True  = Q:CgOp { (box Bool (bool 1)) };
 constant False = Q:CgOp { (box Bool (bool 0)) };
 
-# ought to take a slurpy
-sub infix:<~>($l,$r) { Q:CgOp {
-    (box Str (rawscall String.Concat
-        (unbox String (fetch (methodcall (scopedlex $l) Str)))
-        (unbox String (fetch (methodcall (scopedlex $r) Str)))))
+# taking a slurpy is wrong for this due to flattening.  I'm not sure what is
+# right, maybe **@foo
+sub infix:<~> { Q:CgOp {
+    (letn buf (rawnew System.Text.StringBuilder)
+          i   (int 0)
+          max (getfield Length (getfield pos (callframe)))
+      [whileloop 0 0 (< (l i) (l max)) (prog
+          [rawcall (l buf) Append
+            (unbox String (@ (methodcall (pos (l i)) Str)))]
+          [l i (+ (l i) (int 1))])]
+      [box Str (rawcall (l buf) ToString)])
 } }
 
 sub infix:<+>($l,$r) { Q:CgOp {

CgOp.pm

@@ -572,8 +572,13 @@ use warnings;
     }
 
     sub letn {
-        my ($name, $value, @stuff) = @_;
-        CgOp::Let->new(name => $name, zyg => [ $value, @stuff ]);
+        my (@stuff) = @_;
+        if (blessed($stuff[0])) {
+            @stuff;
+        } else {
+            my ($name, $value) = splice @stuff, 0, 2;
+            CgOp::Let->new(name => $name, zyg => [ $value, letn(@stuff) ]);
+        }
     }
 
     sub pos {

CodeGen.pm

@@ -47,6 +47,9 @@ use 5.010;
         'String' =>
             { Length       => [f => 'Int32'],
               Substring    => [m => 'String'] },
+        'System.Text.StringBuilder' =>
+            { Append       => [m => 'Void'],
+              ToString     => [m => 'String'] },
         'Frame' =>
             { pos          => [f => 'LValue[]'],
               caller       => [f => 'Frame'],

test.pl

@@ -2,7 +2,7 @@
 
 use Test;
 
-plan 135;
+plan 136;
 
 ok 1, "one is true";
 ok 2, "two is also true";
@@ -92,6 +92,7 @@
 
 ok 12 eq "12", "eq stringifies";
 ok ("a" ~ "b") eq "ab", "a + b = ab";
+ok ("a" ~ "b" ~ "c") eq "abc", "a + b + c = abc";
 ok (?1) eq "Bool::True", "True strings to Bool::True";
 ok (?0) eq "Bool::False", "False strings to Bool::False";