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diff --git a/lib/core/operators.nom b/lib/core/operators.nom
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+#!/usr/bin/env nomsu -V6.14
+#
+    This file contains definitions of operators like "+" and "and".
+    
+use "core/metaprogramming"
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+test:
+    assume (all [1 < 2, 2 > 1, 1 <= 2, 2 >= 1, 1 == 1, 1 != 2])
+
+# Comparison Operators
+($x < $y) compiles to "(\($x as lua expr) < \($y as lua expr))"
+($x > $y) compiles to "(\($x as lua expr) > \($y as lua expr))"
+($x <= $y) compiles to "(\($x as lua expr) <= \($y as lua expr))"
+($x >= $y) compiles to "(\($x as lua expr) >= \($y as lua expr))"
+[$a is $b, $a == $b] all compile to "(\($a as lua expr) == \($b as lua expr))"
+[$a isn't $b, $a is not $b, $a not= $b, $a != $b] all compile to
+    "(\($a as lua expr) ~= \($b as lua expr))"
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+test:
+    $x = 10
+    assume ($x == 10)
+    [$x, $y] = [10, 20]
+    unless (($x == 10) and ($y == 20)):
+        fail "mutli-assignment failed."
+    [$x, $y] = [$y, $x]
+    unless (($y == 10) and ($x == 20)):
+        fail "swapping vars failed."
+    $vals = [4, 5]
+    [$x, $y] = (unpack $vals)
+    unless (($x == 4) and ($y == 5)):
+        fail "unpacking failed"
+
+# Variable assignment operator
+($var = $value) compiles to:
+    lua> ("
+        local lua = LuaCode()
+        if \$var.type == "List" then
+            for i, \$assignment in ipairs(\$var) do
+                if i > 1 then lua:add(", ") end
+                local assignment_lua = \($assignment as lua expr)
+                lua:add(assignment_lua)
+                if \$assignment.type == 'Var' then
+                    lua:add_free_vars({assignment_lua:text()})
+                end
+            end
+            lua:add(' = ')
+            if \$value.type == "List" then
+                if #\$value ~= #\$var then
+                    compile_error_at(\$value,
+                        "This assignment has too "..(#\$value > #\$var and "many" or "few").." values.",
+                        "Make sure it has the same number of values on the left and right hand side \
+        ..of the '=' operator.")
+                end
+                for i, \$val in ipairs(\$value) do
+                    if i > 1 then lua:add(", ") end
+                    local val_lua = \($val as lua expr)
+                    lua:add(val_lua)
+                end
+                lua:add(";")
+            else
+                lua:add(\($value as lua expr), ';')
+            end
+        else
+            local var_lua = \($var as lua expr)
+            lua:add(var_lua)
+            if \$var.type == 'Var' then
+                lua:add_free_vars({var_lua:text()})
+            end
+            lua:add(' = ', \($value as lua expr))
+        end
+        return lua
+    ")
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+test:
+    [$foozle, $y] = ["outer", "outer"]
+    externally (set global x local y) means:
+        external $foozle = "inner"
+        $y = "inner"
+    set global x local y
+    unless (($foozle == "inner") and ($y == "outer")): fail "external failed."
+(external $var = $value) compiles to:
+    $lua = ((SyntaxTree {.type = "Action", .source = $var.source, .1 = $var, .2 = "=", .3 = $value}) as lua)
+    $lua, remove free vars
+    return $lua
+test:
+    [$foozle, $y] = ["outer", "outer"]
+    externally (set global x local y) means:
+        with external [$foozle]:
+            $foozle = "inner"
+            $y = "inner"
+    set global x local y
+    unless (($foozle == "inner") and ($y == "outer")):
+        fail "'with external' failed."
+
+(with external $externs $body) compiles to:
+    $body_lua = ($body as lua)
+    lua> ("
+        \$body_lua:remove_free_vars(table.map(\$externs, function(v) return \(nomsu environment):compile(v):text() end))
+    ")
+    return $body_lua
+
+test:
+    [$x, $y] = [1, 2]
+    with [$z, $x = 999]:
+        assume $z == (nil)
+        $z = 999
+        unless ($z == 999):
+            fail "'with' failed."
+        
+        unless ($x == 999):
+            fail "'with' assignment failed."
+    
+    unless ($x == 1):
+        fail "'with' scoping failed"
+    
+    unless ($z == (nil)):
+        fail "'with' scoping failed"
+
+(with $assignments $body) compiles to:
+    lua> ("
+        local \$defs = LuaCode()
+        for i, \$item in ipairs(\$assignments) do
+            if i > 1 then \$defs:add("\\n") end
+            local item_lua = \($item as lua)
+            if \$item.type == 'Action' and \$item.stub == '1 =' then
+                item_lua:remove_free_vars(item_lua.free_vars)
+            end
+            \$defs:add("local ", item_lua, ";")
+        end
+    ")
+    
+    return
+        Lua ("
+            do
+                \$defs
+                \($body as lua)
+            end -- 'with' block
+        ")
+
+# Math Operators
+test:
+    unless ((5 wrapped around 2) == 1):
+        fail "mod not working"
+
+[$x wrapped around $y, $x mod $y] all compile to
+    "((\($x as lua expr)) % (\($y as lua expr)))"
+
+# 3-part chained comparisons
+# (uses a lambda to avoid re-evaluating middle value, while still being an expression)
+test:
+    $calls = 0
+    (one) means:
+        external $calls = ($calls + 1)
+        return 1
+    
+    unless (0 <= (one) <= 2):
+        fail "Three-way chained comparison failed."
+    
+    unless ($calls == 1):
+        fail "Three-way comparison evaluated middle value multiple times"
+($x < $y < $z) parses as ((($a $b $c) -> (($a < $b) and ($b < $c))) $x $y $z)
+($x <= $y < $z) parses as ((($a $b $c) -> (($a <= $b) and ($b < $c))) $x $y $z)
+($x < $y <= $z) parses as ((($a $b $c) -> (($a < $b) and ($b <= $c))) $x $y $z)
+($x <= $y <= $z) parses as ((($a $b $c) -> (($a <= $b) and ($b <= $c))) $x $y $z)
+($x > $y > $z) parses as ((($a $b $c) -> (($a > $b) and ($b > $c))) $x $y $z)
+($x >= $y > $z) parses as ((($a $b $c) -> (($a >= $b) and ($b > $c))) $x $y $z)
+($x > $y >= $z) parses as ((($a $b $c) -> (($a > $b) and ($b >= $c))) $x $y $z)
+($x >= $y >= $z) parses as ((($a $b $c) -> (($a >= $b) and ($b >= $c))) $x $y $z)
+
+# TODO: optimize for common case where x,y,z are all either variables or number literals
+# Boolean Operators
+test:
+    (barfer) means (fail "short circuiting failed")
+    assume (((no) and (barfer)) == (no))
+    assume ((no) or (yes))
+    assume ((yes) or (barfer))
+($x and $y) compiles to "(\($x as lua expr) and \($y as lua expr))"
+($x or $y) compiles to "(\($x as lua expr) or \($y as lua expr))"
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+# Bitwise Operators
+# TODO: implement OR, XOR, AND for multiple operands?
+test:
+    assume ((~ (~ 5)) == 5)
+    assume ((1 | 4) == 5)
+    assume ((1 ~ 3) == 2)
+    assume ((1 & 3) == 1)
+    assume ((1 << 2) == 4)
+    assume ((4 >> 2) == 1)
+
+# Lua 5.3 introduced bit operators like | and &. Use them when possible, otherwise
+    fall back to bit.bor(), bit.band(), etc.
+lua> "if \((is jit) or ((Lua version) == "Lua 5.2")) then"
+[NOT $, ~ $] all compile to "bit.bnot(\($ as lua expr))"
+[$x OR $y, $x | $y] all compile to
+    "bit.bor(\($x as lua expr), \($y as lua expr))"
+
+[$x XOR $y, $x ~ $y] all compile to
+    "bit.bxor(\($x as lua expr), \($y as lua expr))"
+
+[$x AND $y, $x & $y] all compile to
+    "bit.band(\($x as lua expr), \($y as lua expr))"
+
+[$x LSHIFT $shift, $x << $shift] all compile to
+    "bit.lshift(\($x as lua expr), \($shift as lua expr))"
+
+[$x RSHIFT $shift, $x >> $shift] all compile to
+    "bit.rshift(\($x as lua expr), \($shift as lua expr))"
+
+lua> "else"
+[NOT $, ~ $] all compile to "~(\($ as lua expr))"
+[$x OR $y, $x | $y] all compile to "(\($x as lua expr) | \($y as lua expr))"
+[$x XOR $y, $x ~ $y] all compile to "(\($x as lua expr) ~ \($y as lua expr))"
+[$x AND $y, $x & $y] all compile to "(\($x as lua expr) & \($y as lua expr))"
+[$x LSHIFT $shift, $x << $shift] all compile to
+    "(\($x as lua expr) << \($shift as lua expr))"
+
+[$x RSHIFT $shift, $x >> $shift] all compile to
+    "(\($x as lua expr) >> \($shift as lua expr))"
+
+lua> "end"
+
+# Unary operators
+test:
+    assume ((- 5) == -5)
+    assume ((not (yes)) == (no))
+(- $) compiles to "(- \($ as lua expr))"
+(not $) compiles to "(not \($ as lua expr))"
+test:
+    assume ((size of [1, 2, 3]) == 3)
+    assume ((#[1, 2, 3]) == 3)
+[#$list, size of $list] all compile to "(#\($list as lua expr))"
+($list is empty) compiles to "(#\($list as lua expr) == 0)"
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+# Update operators
+test:
+    $x = 1
+    $x += 1
+    unless ($x == 2):
+        fail "+= failed"
+    $x *= 2
+    unless ($x == 4):
+        fail "*= failed"
+    wrap $x around 3
+    unless ($x == 1):
+        fail "wrap around failed"
+($var += $) parses as ($var = (($var or 0) + $))
+($var -= $) parses as ($var = (($var or 0) - $))
+($var *= $) parses as ($var = (($var or 1) * $))
+($var /= $) parses as ($var = ($var / $))
+($var ^= $) parses as ($var = ($var ^ $))
+($var and= $) parses as ($var = ($var and $))
+($var or= $) parses as ($var = ($var or $))
+(wrap $var around $) parses as ($var = ($var wrapped around $))