486 lines
15 KiB
Plaintext
486 lines
15 KiB
Plaintext
#!/usr/bin/env nomsu -V7.0.0
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###
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This file contains compile-time actions that define basic control flow structures
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like "if" statements and loops.
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use "core/metaprogramming"
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use "core/operators"
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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### No-Op
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test:
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do nothing
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(do nothing) compiles to ""
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### Conditionals
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test:
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if (no):
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fail "conditional fail"
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(if $condition $if_body) compiles to ("
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if \($condition as lua expr) then
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\($if_body as lua)
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end
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")
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test:
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unless (yes):
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fail "conditional fail"
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(unless $condition $unless_body) parses as (if (not $condition) $unless_body)
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[
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if $condition $if_body else $else_body, unless $condition $else_body else $if_body
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] all compile to ("
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if \($condition as lua expr) then
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\($if_body as lua)
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else
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\($else_body as lua)
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end
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")
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(else $) compiles to:
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at (this tree) fail ("
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Compile error: This 'else' is not connected to any 'if' or 'unless' condition.
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Hint: You should probably have a ".." in front of the "else", to indicate that it's attached \
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..to the previous condition.
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")
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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### Conditional expression (ternary operator)
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### Note: this uses a function instead of "(condition and if_expr or else_expr)"
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because that breaks if $if_expr is falsey, e.g. "x < 5 and false or 99"
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test:
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assume ((1 if (yes) else 2) == 1)
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assume ((1 if (no) else 2) == 2)
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[
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$when_true_expr if $condition else $when_false_expr
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$when_true_expr if $condition otherwise $when_false_expr
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$when_false_expr unless $condition else $when_true_expr
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$when_false_expr unless $condition then $when_true_expr
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] all compile to:
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### If $when_true_expr is guaranteed to be truthy, we can use Lua's idiomatic
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equivalent of a conditional expression: (cond and if_true or if_false)
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if {.Text, .List, .Dict, .Number}.($when_true_expr.type):
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return Lua ("
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(\($condition as lua expr) and \($when_true_expr as lua expr) or \
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..\($when_false_expr as lua expr))
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")
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..else:
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### Otherwise, need to do an anonymous inline function (yuck, too bad lua
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doesn't have a proper ternary operator!)
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To see why this is necessary consider: (random()<.5 and false or 99)
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return Lua ("
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((function()
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if \($condition as lua expr) then
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return \($when_true_expr as lua expr)
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else
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return \($when_false_expr as lua expr)
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end
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end)())
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")
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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### GOTOs
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test:
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$i = 0
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--- $loop ---
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$i += 1
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unless ($i == 10):
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go to $loop
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assume ($i == 10)
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--- (Loop) ---
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$i -= 1
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unless ($i == 0):
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go to (Loop)
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assume ($i == 0)
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(--- $label ---) compiles to ("
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::label_\(
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($label.stub, as lua id) if ($label.type == "Action") else
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$label as lua identifier
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)::
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")
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(go to $label) compiles to ("
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goto label_\(
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($label.stub, as lua id) if ($label.type == "Action") else
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$label as lua identifier
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)
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")
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### Basic loop control
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(stop $var) compiles to:
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if $var:
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return Lua "goto stop_\($var as lua identifier)"
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..else:
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return Lua "break"
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(do next $var) compiles to:
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if $var:
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return Lua "goto continue_\($var as lua identifier)"
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..else:
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return Lua "goto continue"
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(---stop $var ---) compiles to "::stop_\($var as lua identifier)::"
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(---next $var ---) compiles to "::continue_\($var as lua identifier)::"
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### While loops
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test:
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$x = 0
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repeat while ($x < 10): $x += 1
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assume ($x == 10)
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repeat while ($x < 20): stop
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assume ($x == 10)
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repeat while ($x < 20):
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$x += 1
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if (yes):
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do next
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fail "Failed to 'do next'"
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assume ($x == 20)
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(repeat while $condition $body) compiles to:
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$lua =
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Lua ("
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while \($condition as lua expr) do
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\($body as lua)
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")
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if ($body, contains \(do next)):
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$lua, add "\n ::continue::"
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$lua, add "\nend --while-loop"
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return $lua
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(repeat $body) parses as (repeat while (yes) $body)
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(repeat until $condition $body) parses as (repeat while (not $condition) $body)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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### For-each loop (lua's "ipairs()")
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(for $var in $iterable $body) compiles to:
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unless $var:
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at (this tree) fail "No var here"
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### This uses Lua's approach of only allowing loop-scoped variables in a loop
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if (($var.type == "Action") and ($var.stub == "1 =")):
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[$key, $value] = [$var.1, $var.3]
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..else:
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[$key, $value] = [nil, $var]
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unless $value:
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at (this tree) fail "No value here"
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### Numeric loop:
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if (($iterable.type == "Action") and (($iterable, get stub) == "1 to")):
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[$start, $stop] = [$iterable.1, $iterable.3]
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$loop =
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Lua ("
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local _start = \($start as lua expr)
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for \($value as lua identifier)=_start,\($stop as lua expr) do
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")
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if $key:
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$loop, add ("
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local \($key as lua identifier) = \($value as lua identifier) - _start + 1;
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")
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go to (loop set)
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### Numeric loop with step:
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if (($iterable.type == "Action") and (($iterable, get stub) == "1 to 2 by")):
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[$start, $stop, $step] = [$iterable.1, $iterable.3, $iterable.5]
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$loop =
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Lua ("
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local _start, _step = \($start as lua expr), \($step as lua expr);
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for \($value as lua identifier)=_start,\($stop as lua expr),_step do
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")
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if $key:
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$loop, add ("
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local \($key as lua identifier) = (\($value as lua identifier) - _start)/_step + 1
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")
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go to (loop set)
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### for $ in (...):
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if $key:
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$loop =
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Lua ("
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for \($key as lua identifier),\($value as lua identifier) in pairs(\
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..\($iterable as lua expr)) do
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")
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..else:
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$loop =
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Lua "for _i,\($value as lua identifier) in _ipairs(\($iterable as lua expr)) do"
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--- (loop set) ---
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### TODO: don't always wrap in block
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$lua =
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Lua ("
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do -- for-loop
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\$loop
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\;
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")
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$lua, add ($body as lua)
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if ($body, contains \(do next)):
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$lua, add "\n ::continue::"
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if ($key and ($body, contains \(do next \$key))):
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$lua, add "\n " (\(---next \$key ---) as lua)
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if ($body, contains \(do next \$value)):
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$lua, add "\n " (\(---next \$value ---) as lua)
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$lua, add "\n end"
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if ($key and ($body, contains \(stop \$key))):
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$lua, add "\n " (\(---stop \$key ---) as lua)
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if ($body, contains \(stop \$value)):
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$lua, add "\n " (\(---stop \$value ---) as lua)
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$lua, add "\nend -- for-loop"
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$lua, remove free vars
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[($value as lua identifier, text), $key and ($key as lua identifier, text)]
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return $lua
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test:
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$d = {.a = 10, .b = 20, .c = 30, .d = 40, .e = 50}
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$result = []
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for ($k = $v) in $d:
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if ($k == "a"):
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do next $k
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if ($v == 20):
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do next $v
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$result, add "\$k = \$v"
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assume (($result sorted) == ["c = 30", "d = 40", "e = 50"])
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### Numeric range for loops
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test:
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assume ([: for $ in (1 to 5): add $] == [1, 2, 3, 4, 5])
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assume ([: for $ in (1 to 5 by 2): add $] == [1, 3, 5])
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assume ([: for $ in (5 to 1): add $] == [])
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$nums = []
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for $outer in (1 to 100):
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for $inner in ($outer to ($outer + 2)):
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if ($inner == 2):
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$nums, add -2
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do next $inner
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$nums, add $inner
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if ($inner == 5):
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stop $outer
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assume ($nums == [1, -2, 3, -2, 3, 4, 3, 4, 5])
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### repeat $n times is a shorthand:
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test:
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$x = 0
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repeat 5 times:
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$x += 1
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assume $x == 5
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(repeat $n times $body) parses as (for (=lua "_i") in (1 to $n by 1) $body)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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test:
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when:
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(1 == 2) (100 < 0):
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fail "bad conditional"
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(1 == 0) (1 == 1) $not_a_variable.x: do nothing
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(1 == 1):
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fail "bad conditional"
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(1 == 2):
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fail "bad conditional"
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else:
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fail "bad conditional"
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### Multi-branch conditional (if..elseif..else)
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(when $body) compiles to:
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$code = (Lua "")
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$clause = "if"
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$else_allowed = (yes)
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unless ($body.type == "Block"):
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at $body fail ("
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Compile error: 'if' expected a Block, but got a \($body.type).
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Hint: Perhaps you forgot to put a ':' after 'if'?
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")
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for $line in $body:
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unless
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(($line.type == "Action") and (#$line >= 2)) and
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$line.(#$line) is "Block" syntax tree
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..:
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at $line fail ("
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Compile error: Invalid line for the body of an 'if' block.
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Hint: Each line should contain one or more conditional expressions followed by a block, \
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..or "else" followed by a block.
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")
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$action = $line.(#$line)
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if (($line.1 == "else") and (#$line == 2)):
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unless $else_allowed:
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at $line fail ("
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Compile error: You can't have two 'else' blocks.
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Hint: Merge all of the 'else' blocks together.
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")
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unless (#"\$code" > 0):
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at $line fail ("
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Compile error: You can't have an 'else' block without a preceding condition.
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Hint: If you want the code in this block to always execute, you don't need a conditional \
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..block around it. Otherwise, make sure the 'else' block comes last.
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")
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$code, add "\nelse\n " ($action as lua)
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$else_allowed = (no)
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..else:
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$code, add $clause " "
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for $i in (1 to (#$line - 1)):
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if ($i > 1):
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$code, add " or "
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$code, add ($line.$i as lua expr)
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$code, add " then\n " ($action as lua)
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$clause = "\nelseif"
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if (#"\$code" == 0):
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at $body fail ("
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Compile error: 'if' block has an empty body.
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Hint: This means nothing would happen, so the 'if' block should be deleted.
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")
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$code, add "\nend --when"
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return $code
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test:
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if 5 is:
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1 2 3:
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fail "bad switch statement"
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4 5:
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do nothing
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5 6:
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fail "bad switch statement"
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else:
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fail "bad switch statement"
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### Switch statement
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[if $branch_value is $body, when $branch_value is $body] all compile to:
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$code = (Lua "")
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$clause = "if"
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$else_allowed = (yes)
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define mangler
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unless ($body.type == "Block"):
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at $body fail ("
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Compile error: 'if' expected a Block, but got a \($body.type).
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Hint: Perhaps you forgot to put a ':' after the 'is'?
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")
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for $line in $body:
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unless
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(($line.type == "Action") and (#$line >= 2)) and
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$line.(#$line) is "Block" syntax tree
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..:
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at $line fail ("
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Compile error: Invalid line for 'if' block.
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Hint: Each line should contain expressions followed by a block, or "else" followed by a block.
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")
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$action = $line.(#$line)
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if (($line.1 == "else") and (#$line == 2)):
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unless $else_allowed:
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at $line fail ("
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Compile error: You can't have two 'else' blocks.
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Hint: Merge all of the 'else' blocks together.
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")
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unless (#"\$code" > 0):
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at $line fail ("
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Compile error: You can't have an 'else' block without a preceding condition.
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Hint: If you want the code in this block to always execute, you don't need a conditional \
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..block around it. Otherwise, make sure the 'else' block comes last.
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")
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$code, add "\nelse\n " ($action as lua)
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$else_allowed = (no)
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..else:
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$code, add $clause " "
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for $i in (1 to (#$line - 1)):
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if ($i > 1):
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$code, add " or "
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$code, add "\(mangle "branch value") == " ($line.$i as lua expr)
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$code, add " then\n " ($action as lua)
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$clause = "\nelseif"
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if (#"\$code" == 0):
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at $body fail ("
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Compile error: 'if' block has an empty body.
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Hint: This means nothing would happen, so the 'if' block should be deleted.
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")
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$code, add "\nend --when"
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return Lua ("
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do --if $ is...
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local \(mangle "branch value") = \($branch_value as lua expr)
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\$code
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end -- if $ is...
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")
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### Do/finally
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(do $action) compiles to ("
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do
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\($action as lua)
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end -- do
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")
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test:
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assume ((result of: return 99) == 99)
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### Inline thunk:
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(result of $body) compiles to "\(\(->(\$body)) as lua)()"
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test:
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$t = [1, [2, [[3], 4], 5, [[[6]]]]]
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$flat = []
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for $ in recursive $t:
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if ((lua type of $) == "table"):
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for $2 in $:
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recurse $ on $2
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..else:
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$flat, add $
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assume (sorted $flat) == [1, 2, 3, 4, 5, 6]
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### Recurion control flow
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(recurse $v on $x) compiles to
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Lua "table.insert(_stack_\($v as lua expr), \($x as lua expr))"
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(for $var in recursive $structure $body) compiles to:
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$lua =
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Lua ("
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do
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local _stack_\($var as lua expr) = a_List{\($structure as lua expr)}
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while #_stack_\($var as lua expr) > 0 do
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\($var as lua expr) = table.remove(_stack_\($var as lua expr), 1)
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\($body as lua)
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")
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if ($body, contains \(do next)):
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$lua, add "\n ::continue::"
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if ($body, contains \(do next \$var)):
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$lua, add "\n \(\(---next \$var ---) as lua)"
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$lua, add "\n end -- Recursive loop"
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if ($body, contains \(stop \$var)):
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$lua, add "\n \(\(---stop \$var ---) as lua)"
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$lua, add "\nend -- Recursive scope"
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return $lua |