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Consolidating iteration around iterable ranges (and case-specific

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optimizations when possible).
This commit is contained in:
Bruce Hill 2019-03-09 15:59:54 -08:00
parent c6734d82e9
commit 06c8737897
1 changed files with 68 additions and 70 deletions
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138
lib/core/control_flow.nom
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@ -161,31 +161,71 @@ test:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# For-each loop (lua's "ipairs()")
(for $var in $iterable at $i $body) compiles to:
(for $var in $iterable $body) compiles to:
unless $var:
at (this tree) fail "No var here"
# This uses Lua's approach of only allowing loop-scoped variables in a loop
if (($var.type == "Action") and ($var.stub == "1 =")):
[$key, $value] = [$var.1, $var.3]
go to (vars set)
if (($var.type == "Action") and ($var.stub == "1 at")):
[$key, $value] = [$var.3, $var.1]
..else:
[$key, $value] = [nil, $var]
--- (vars set) ---
unless $value:
at (this tree) fail "No value here"
# Numeric loop:
if (($iterable.type == "Action") and (($iterable, get stub) == "1 to")):
[$start, $stop] = [$iterable.1, $iterable.3]
$loop =
Lua ("
local _start = \($start as lua expr)
for \($var as lua identifier)=_start,\($stop as lua expr) do
\($i as lua identifier) = \($var as lua identifier) - _start + 1
for \($value as lua identifier)=_start,\($stop as lua expr) do
")
if $key:
$loop, add ("
local \($key as lua identifier) = \($value as lua identifier) - _start + 1;
")
go to (loop set)
# Numeric loop with step:
if (($iterable.type == "Action") and (($iterable, get stub) == "1 to 2 by")):
[$start, $stop, $step] = [$iterable.1, $iterable.3, $iterable.5]
$loop =
Lua ("
local _start, _step = \($start as lua expr), \($step as lua expr)
for \($var as lua identifier)=_start,\($stop as lua expr),_step do
\($i as lua identifier) = (\($var as lua identifier) - _start)/_step + 1
local _start, _step = \($start as lua expr), \($step as lua expr);
for \($value as lua identifier)=_start,\($stop as lua expr),_step do
")
unless $loop:
if $key:
$loop, add ("
local \($key as lua identifier) = (\($value as lua identifier) - _start)/_step + 1
")
go to (loop set)
# for $ in (...):
if $key:
$loop =
Lua ("
local _iterating = _1_as_list(\($iterable as lua expr))
for \($i as lua identifier)=1,#_iterating do
\($var as lua identifier) = _iterating[\($i as lua identifier)]
local _iterating = \($iterable as lua expr);
local _next = getmetatable(_iterating).__next or next;
for \($key as lua identifier),\($value as lua identifier) in _next,_iterating,nil do
if \($value as lua identifier) == nil and _1_is_a_dead_coroutine(_iterating) then break end
")
..else:
$loop =
Lua ("
local _iterating = _1_as_an_iterable(\($iterable as lua expr))
for _i=1,#_iterating do
local \($value as lua identifier) = _iterating[_i]
if \($value as lua identifier) == nil and _1_is_a_dead_coroutine(_iterating) then break end
")
--- (loop set) ---
$lua =
Lua ("
do -- for-loop
@ -196,17 +236,27 @@ test:
if ($body has subtree \(do next)):
$lua, add "\n ::continue::"
if ($body has subtree \(do next $var)):
$lua, add "\n " (\(---next $var ---) as lua)
if ($key and ($body has subtree \(do next $key))):
$lua, add "\n " (\(---next $key ---) as lua)
if ($body has subtree \(do next $value)):
$lua, add "\n " (\(---next $value ---) as lua)
$lua, add "\n end"
if ($body has subtree \(stop $var)):
$lua, add "\n " (\(---stop $var ---) as lua)
if ($key and ($body has subtree \(stop $key))):
$lua, add "\n " (\(---stop $key ---) as lua)
if ($body has subtree \(stop $value)):
$lua, add "\n " (\(---stop $value ---) as lua)
$lua, add "\nend -- for-loop"
$lua, remove free vars [($value as lua identifier, text), $key and ($key as lua identifier, text)]
return $lua
(for $var in $iterable $body) parses as
for $var in $iterable at (=lua "_i") $body
# TODO: remove these shims:
(for $var in $iterable at $i $body) parses as
for ($i = $var) in $iterable $body
(for $k = $v in $iterable $body) parses as
for ($k = $v) in $iterable $body
test:
$d = {.a = 10, .b = 20, .c = 30, .d = 40, .e = 50}
@ -237,7 +287,7 @@ test:
stop $outer
assume ($nums == [1, -2, 3, -2, 3, 4, 3, 4, 5])
# These are shims, and should be phased out:
# TODO: These are shims, and should be phased out:
[
for $var in $start to $stop by $step $body
for $var in $start to $stop via $step $body
@ -253,59 +303,7 @@ test:
$x += 1
assume $x == 5
(repeat $n times $body) parses as (for (=lua "_XXX_") in (1 to $n by 1) $body)
# Dict iteration (lua's "pairs()")
test:
$a = [10, 20, 30, 40, 50]
$b = []
for $x in $a:
$b, add $x
assume ($a == $b)
$b = []
for $x in $a:
if ($x == 10):
do next $x
if ($x == 50):
stop $x
$b, add $x
assume ($b == [20, 30, 40])
# Small memory footprint:
assume (1 to (1 << 31))
[for $key = $value in $iterable $body, for $key $value in $iterable $body]
..all compile to:
$lua =
Lua ("
for \($key as lua identifier),\($value as lua identifier) in pairs(\
..\($iterable as lua expr)) do
")
$lua, add "\n " ($body as lua)
if ($body has subtree \(do next)):
$lua, add "\n ::continue::"
if ($body has subtree \(do next $key)):
$lua, add "\n " (\(---next $key ---) as lua)
if ($body has subtree \(do next $value)):
$lua, add "\n " (\(---next $value ---) as lua)
$lua, add "\nend --foreach-loop"
$stop_labels = (Lua "")
if ($body has subtree \(stop $key)):
$stop_labels, add "\n" (\(---stop $key ---) as lua)
if ($body has subtree \(stop $value)):
$stop_labels, add "\n" (\(---stop $value ---) as lua)
if ((size of "\$stop_labels") > 0):
$inner_lua = $lua
$lua = (Lua "do -- scope for stopping for $ = $ loop\n ")
$lua, add $inner_lua $stop_labels "\nend"
return $lua
(repeat $n times $body) parses as (for (=lua "_i") in (1 to $n by 1) $body)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~