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Updating example

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Bruce Hill 2019-01-01 17:31:50 -08:00
parent ad6c5172e8
commit 0507d8de8c
1 changed files with 18 additions and 12 deletions
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30
examples/how_do_i.nom
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@ -302,36 +302,42 @@ debug only:
# How do I use an action as a value? # How do I use an action as a value?
# Well... it's always *possible* to fall back to Lua behavior for something like this: # Well... it's always *possible* to fall back to Lua behavior for something like this:
(best of $items according to $key_fn) means: (best of $items according to $key_fn) means:
$best = (nil) [$best, $best_key] = [nil, nil]
$best_key = (nil)
for $item in $items: for $item in $items:
$key = ($key_fn $item) $key = ($key_fn $item)
if (($best is (nil)) or ($key > $best_key)): if (($best is (nil)) or ($key > $best_key)):
$best = $item [$best, $best_key] = [$item, $key]
$best_key = $key
return $best return $best
# Function literals look like: $x -> ($x * $x) # Function literals look like: $x -> ($x * $x)
say (best of [2, -3, 4, -8] according to ($x -> ($x * $x))) say (best of [2, -3, 4, -8] according to ($x -> ($x * $x)))
# Or, you can use $(foo $) to access the function that gets called by (foo $) # Or, you can surround an action with $(...) to refer to it:
($x squared) means ($x * $x) ($x squared) means ($x * $x)
say (best of [2, -3, 4, -8] according to $($ squared)) say (best of [2, -3, 4, -8] according to $($ squared))
# But nomsu was designed with flexible alternatives that are often better than passing functions. # However, nomsu was designed with flexible alternatives that are often better
For example, instead of calling a key function on every item, you could instead define a macro than passing functions. For example, instead of calling a key function on
that gives you a value based on an inlined expression: every item, you could instead define a macro that will inline an expression
to produce faster code:
(best of $items where $item has score $key_expr) parses as (best of $items where $item has score $key_expr) parses as
result of: result of:
$best = (nil) [$best, $best_key] = [nil, nil]
$best_key = (nil)
for $item in $items: for $item in $items:
$key = $key_expr $key = $key_expr
if (($best is (nil)) or ($key > $best_key)): if (($best is (nil)) or ($key > $best_key)):
$best = $item [$best, $best_key] = [$item, $key]
$best_key = $key
return $best return $best
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
say (best of [2, -3, 4, -8] where $x has score ($x * $x)) say (best of [2, -3, 4, -8] where $x has score ($x * $x))
# The line above expands to:
say
result of:
[$best, $best_key] = [nil, nil]
for $x in [2, -3, 4, -8]:
$key = ($x * $x)
if (($best is (nil)) or ($key > $best_key)):
[$best, $best_key] = [$x, $key]
return $best