use if-zero in a few more places

basis/calendar/calendar.factor

@@ -45,11 +45,11 @@ M: not-a-month summary
 
 PRIVATE>
 
-: month-names ( -- array )
+CONSTANT: month-names 
     {
         "January" "February" "March" "April" "May" "June"
         "July" "August" "September" "October" "November" "December"
-    } ;
+    }
 
 : month-name ( n -- string )
     check-month 1- month-names nth ;

basis/io/sockets/unix/unix.factor

@@ -19,7 +19,7 @@ IN: io.sockets.unix
     [ handle-fd ] 2dip 1 <int> "int" heap-size setsockopt io-error ;
 
 M: unix addrinfo-error ( n -- )
-    dup zero? [ drop ] [ gai_strerror throw ] if ;
+    [ gai_strerror throw ] unless-zero ;
 
 ! Client sockets - TCP and Unix domain
 M: object (get-local-address) ( handle remote -- sockaddr )

basis/math/bits/bits.factor

@@ -7,7 +7,7 @@ TUPLE: bits { number read-only } { length read-only } ;
 C: <bits> bits
 
 : make-bits ( number -- bits )
-    dup zero? [ drop T{ bits f 0 0 } ] [ dup abs log2 1 + <bits> ] if ; inline
+    [ T{ bits f 0 0 } ] [ dup abs log2 1 + <bits> ] if-zero ; inline
 
 M: bits length length>> ;
 

basis/math/functions/functions.factor

@@ -71,7 +71,7 @@ PRIVATE>
     2dup [ real? ] both? [ drop 0 >= ] [ 2drop f ] if ; inline
 
 : 0^ ( x -- z )
-    dup zero? [ drop 0/0. ] [ 0 < 1/0. 0 ? ] if ; inline
+    [ 0/0. ] [ 0 < 1/0. 0 ? ] if-zero ; inline
 
 : (^mod) ( n x y -- z )
     make-bits 1 [
@@ -263,13 +263,13 @@ M: real atan fatan ;
 : round ( x -- y ) dup sgn 2 / + truncate ; inline
 
 : floor ( x -- y )
-    dup 1 mod dup zero?
+    dup 1 mod
-    [ drop ] [ dup 0 < [ - 1 - ] [ - ] if ] if ; foldable
+    [ ] [ dup 0 < [ - 1 - ] [ - ] if ] if-zero ; foldable
 
 : ceiling ( x -- y ) neg floor neg ; foldable
 
 : floor-to ( x step -- y )
-    dup zero? [ drop ] [ [ / floor ] [ * ] bi ] if ;
+    [ [ / floor ] [ * ] bi ] unless-zero ;
 
 : lerp ( a b t -- a_t ) [ over - ] dip * + ; inline
 

basis/math/primes/erato/erato.factor

@@ -9,7 +9,7 @@ IN: math.primes.erato
 CONSTANT: masks B{ 0 128 0 0 0 0 0 64 0 0 0 32 0 16 0 0 0 8 0 4 0 0 0 2 0 0 0 0 0 1 }
 
 : bit-pos ( n -- byte/f mask/f )
-    30 /mod masks nth-unsafe dup zero? [ 2drop f f ] when ;
+    30 /mod masks nth-unsafe [ drop f f ] when-zero ;
 
 : marked-unsafe? ( n arr -- ? )
     [ bit-pos ] dip swap [ [ nth-unsafe ] [ bitand zero? not ] bi* ] [ 2drop f ] if* ;

basis/math/ratios/ratios.factor

@@ -1,6 +1,7 @@
 ! Copyright (C) 2004, 2008 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: accessors kernel kernel.private math math.functions math.private ;
+USING: accessors kernel kernel.private math math.functions
+math.private sequences summary ;
 IN: math.ratios
 
 : 2>fraction ( a/b c/d -- a c b d )
@@ -19,13 +20,18 @@ IN: math.ratios
 
 PRIVATE>
 
+ERROR: division-by-zero ;
+
+M: division-by-zero summary
+    drop "Division by zero" ;
+
 M: integer /
-    dup zero? [
+    [
-        "Division by zero" throw
+        division-by-zero
     ] [
         dup 0 < [ [ neg ] bi@ ] when
         2dup gcd nip [ /i ] curry bi@ fraction>
-    ] if ;
+    ] if-zero ;
 
 M: ratio hashcode*
     nip >fraction [ hashcode ] bi@ bitxor ;

basis/serialize/serialize.factor

@@ -47,7 +47,7 @@ M: id equal? over id? [ [ obj>> ] bi@ eq? ] [ 2drop f ] if ;
 ! The last case is needed because a very large number would
 ! otherwise be confused with a small number.
 : serialize-cell ( n -- )
-    dup zero? [ drop 0 write1 ] [
+    [ 0 write1 ] [
         dup HEX: 7e <= [
             HEX: 80 bitor write1
         ] [
@@ -60,7 +60,7 @@ M: id equal? over id? [ [ obj>> ] bi@ eq? ] [ 2drop f ] if ;
             ] if
             >be write
         ] if
-    ] if ;
+    ] if-zero ;
 
 : deserialize-cell ( -- n )
     read1 {
@@ -79,12 +79,12 @@ M: f (serialize) ( obj -- )
     drop CHAR: n write1 ;
 
 M: integer (serialize) ( obj -- )
-    dup zero? [
+    [
-        drop CHAR: z write1
+        CHAR: z write1
     ] [
         dup 0 < [ neg CHAR: m ] [ CHAR: p ] if write1
         serialize-cell
-    ] if ;
+    ] if-zero ;
 
 M: float (serialize) ( obj -- )
     CHAR: F write1

basis/windows/errors/errors.factor

@@ -713,11 +713,7 @@ ERROR: error-message-failed id ;
     GetLastError n>win32-error-string ;
 
 : (win32-error) ( n -- )
-    dup zero? [
+    [ win32-error-string throw ] unless-zero ;
-        drop
-    ] [
-        win32-error-string throw
-    ] if ;
 
 : win32-error ( -- )
     GetLastError (win32-error) ;

extra/benchmark/fasta/fasta.factor

@@ -63,7 +63,7 @@ CONSTANT: homo-sapiens
 :: split-lines ( n quot -- )
     n line-length /mod
     [ [ line-length quot call ] times ] dip
-    dup zero? [ drop ] quot if ; inline
+    quot unless-zero ; inline
 
 : write-random-fasta ( seed n chars floats desc id -- seed )
     write-description

extra/game-loop/game-loop.factor

@@ -1,5 +1,6 @@
 USING: accessors calendar continuations destructors kernel math
-math.order namespaces system threads ui ui.gadgets.worlds ;
+math.order namespaces system threads ui ui.gadgets.worlds
+sequences ;
 IN: game-loop
 
 TUPLE: game-loop
@@ -52,11 +53,11 @@ TUPLE: game-loop-error game-loop error ;
     drop ;
 
 : ?tick ( loop count -- )
-    dup zero? [ drop millis >>last-tick drop ] [
+    [ millis >>last-tick drop ] [
         over [ since-last-tick ] [ tick-length>> ] bi >=
         [ [ drop increment-tick ] [ drop tick ] [ 1- ?tick ] 2tri ]
         [ 2drop ] if
-    ] if ;
+    ] if-zero ;
 
 : (run-loop) ( loop -- )
     dup running?>>