diff --git a/src/lambda-calculus.js b/src/lambda-calculus.js
index 807410b..e68604d 100644
--- a/src/lambda-calculus.js
+++ b/src/lambda-calculus.js
@@ -221,10 +221,12 @@ function parse(code) {
     function name(i) {
       if ( code[i]==='_' ) {
         while ( identifierChars.test( code[i] || "" ) ) i++;
+        if ( code[i]==='?' ) i++;
         return [sp(i),"_"];
       } else if ( letters.test( code[i] || "" ) ) {
         let j = i+1;
         while ( identifierChars.test( code[j] || "" ) ) j++;
+        if ( code[j]==='?' ) j++;
         return [sp(j),code.slice(i,j)];
       } else
         return null;
diff --git a/tests/basics-binary-scott/solution.txt b/tests/basics-binary-scott/solution.txt
index de9984f..174711b 100644
--- a/tests/basics-binary-scott/solution.txt
+++ b/tests/basics-binary-scott/solution.txt
@@ -56,12 +56,12 @@ shiftL  = \ n . n 0 I I                   # mind that a shiftL in LE is a divisi
 
 dbl = \ n . n 0 (K (shiftR0 n)) (K (shiftR0 n))
 
-isStrictZero = \ n . n True (K False) (K False) # disallow padding zeroes # O(1)
-isZero       = \ n . n True    isZero (K False) #    allow padding zeroes # amortised O(2), so don't worry too much
+isStrictZero? = \ n . n True (K False) (K False) # disallow padding zeroes # O(1)
+isZero?       = \ n . n True   isZero? (K False) #    allow padding zeroes # amortised O(2), so don't worry too much
 
 pad = \ n . n (shiftR0 0) (B shiftR0 pad) (B shiftR1 pad)
-unpad = \ n . n 0 ( \ z . ( \ unpadZ . isStrictZero unpadZ (shiftR0 unpadZ) 0 ) (unpad z) ) (B shiftR1 unpad)
-isPadded = \ n . n False ( \ z . z True (K (isPadded z)) (K (isPadded z)) ) isPadded
+unpad = \ n . n 0 ( \ z . ( \ unpadZ . isStrictZero? unpadZ (shiftR0 unpadZ) 0 ) (unpad z) ) (B shiftR1 unpad)
+isPadded? = \ n . n False ( \ z . z True (K (isPadded? z)) (K (isPadded? z)) ) isPadded?
 
 # instance Ord
 
@@ -99,11 +99,11 @@ bitXor = \ m n . m n
                    ( \ zm . n (    dbl zm) (B     dbl (bitXor zm)) (B shiftR1 (bitXor zm)) )
                    ( \ zm . n (shiftR1 zm) (B shiftR1 (bitXor zm)) (B     dbl (bitXor zm)) )
 
-testBit = \ i n . isZero i
+testBit = \ i n . isZero? i
                     (n False (testBit (pred i)) (testBit (pred i)))
                     (n False (K False)          (K True))
 
-bit = \ i . isZero i (shiftR0 (bit (pred i))) (succ i)
+bit = \ i . isZero? i (shiftR0 (bit (pred i))) (succ i)
 
 popCount = \ n . n 0 popCount (B succ popCount)
 
@@ -139,7 +139,7 @@ minus = \ m n . gt m n 0 (go m n)
 
 until = \ p fn x . p x (until p fn (fn x)) x
 divMod = \ m n . until (B (lt m) snd) (bimap succ shiftR0) (Pair 0 n)
-                 \ steps nn . isZero steps
+                 \ steps nn . isZero? steps
                                 (divMod (minus m (shiftL nn)) n (B Pair (plus (bit (pred steps)))))
                                 (Pair 0 m)
 div = \ m n . fst (divMod m n)
@@ -160,7 +160,7 @@ gcd = \ m n . m n
                                      (gcd (minus m n) n)
                            )
                 )
-lcm = \ m n . T (gcd m n) \ g . isZero g (times (div m g) n) g
+lcm = \ m n . T (gcd m n) \ g . isZero? g (times (div m g) n) g
 
 min = \ m n . le m n n m
 max = \ m n . le m n m n
diff --git a/tests/basics-binary-scott/test.js b/tests/basics-binary-scott/test.js
index b7b1124..d8ec89d 100644
--- a/tests/basics-binary-scott/test.js
+++ b/tests/basics-binary-scott/test.js
@@ -11,7 +11,7 @@ const {fromInt,toInt} = LC;
 const {False,True,not,and,or,xor,implies} = solution;
 const {LT,EQ,GT,compare,lt,le,eq,ge,gt} = solution;
 const {Pair,fst,snd,first,second,both,bimap,curry} = solution;
-const {shiftR0,shiftR1,shiftL,dbl,isStrictZero,isZero,pad,unpad,isPadded} = solution;
+const {shiftR0,shiftR1,shiftL,dbl,isStrictZero,isZero,pad,unpad,"isPadded?":isPadded} = solution;
 const {succ,pred} = solution;
 const {bitAnd,bitOr,bitXor,testBit,bit,popCount,even,odd} = solution;
 const {plus,times,minus,divMod,div,mod,pow,gcd,lcm,min,max} = solution;