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// Comment to end of line

// Process data in a pipeline with steps separated by ->
// String literals are delimited by single quotes
// A bang (!) indicates a sink, or end of the pipe
// OUT is the standard output object, ::write is the message to write output
'Hello, World!' -> !OUT::write

// Output a newline by just entering it in the string (multiline strings)
'
' -> !OUT::write
// Or output the decimal unicode value for newline (10) between $# and ;
'$#10;' -> !OUT::write

// Define an immutable named value. Value syntax is very literal.
def names: ['Adam', 'George', 'Jenny', 'Lucy'];

// Stream the list to process each name. Note the use of $ to get the value.
// The current value in the pipeline is always just $
// String interpolation starts with a $ and ends with ;
$names... -> 'Hello $;!
' -> !OUT::write

// You can also stream in the interpolation and nest interpolations
// Note the list indexing with parentheses and the slice extraction
// Note the use of ~ to signify an exclusive bound to the range
// Outputs 'Hello Adam, George, Jenny and Lucy!'
'Hello $names(first);$names(first~..~last)... -> ', $;'; and $names(last);!
' -> !OUT::write

// Conditionally say different things to different people
// Matchers (conditional expressions) are delimited by angle brackets
// A set of matchers, evaluated top down, must be in templates (a function)
// Here it is an inline templates delimited by \( to \)
// Note the doubled '' and $$ to get a literal ' and $
$names... -> \(
  when <='Adam'> do 'What''s up $;?' !
  when <='George'> do 'George, where are the $$10 you owe me?' !
  otherwise 'Hello $;!' !
\) -> '$;$#10;' -> !OUT::write

// You can also define templates (functions)
// A lone ! emits the value into the calling pipeline without returning control
// The # sends the value to be matched by the matchers 
// Note that templates always take one input value and emit 0 or more outputs
templates collatz-sequence
  when <..0> do 'The start seed must be a positive integer' !
  when <=1> do $!
// The ?( to ) allows matching a computed value. Can be concatenated as "and"
  when <?($ mod 2 <=1>)> do
    $ !
    3 * $ + 1 -> #
  otherwise
    $ !
    $ ~/ 2 -> #
end collatz-sequence

// Collatz sequence from random start on one line separated by spaces
1000 -> SYS::randomInt -> $ + 1 -> collatz-sequence -> '$; ' -> !OUT::write
'
' -> !OUT::write

// Collatz sequence formatted ten per line by an indexed list template
// Note the square brackets creates a list of the enclosed pipeline results
// The \[i]( to \) defines a templates to apply to each value of a list,
// the i (or whatever identifier you choose) holds the index
[1000 -> SYS::randomInt -> $ + 1 -> collatz-sequence]
-> \[i](
  when <=1|?($i mod 10 <=0>)> do '$;$#10;' !
  otherwise '$; ' !
\)... -> !OUT::write

// A range can have an optional stride
def odd-numbers: [1..100:2];

// Use mutable state locally. One variable per templates, always called @
templates product
  @: $(first);
  $(first~..last)... -> @: $@ * $;
  $@ !
end product

$odd-numbers(6..8) -> product -> !OUT::write
'
' -> !OUT::write

// Use processor objects to hold mutable state.
// Note that the outer @ must be referred to by name in inner contexts
// A sink templates gives no output and is called prefixed by !
// A source templates takes no input and is called prefixed by $
processor Product
  @: 1;
  sink accumulate
    @Product: $@Product * $;
  end accumulate
  source result
    $@Product !
  end result
end Product

// The processor is a constructor templates. This one called with $ (no input)
def multiplier: $Product;

// Call object templates by sending messages with ::
1..7 -> !multiplier::accumulate
-1 -> !multiplier::accumulate
$multiplier::result -> 'The product is $;
' -> !OUT::write

// Syntax sugar for a processor implementing the collector interface
1..7 -> ..=Product -> 'The collected product is $;$#10;' -> !OUT::write

// Symbol sets (essentially enums) can be defined for finite sets of values
data colour #{green, red, blue, yellow}

// Use processor typestates to model state cleanly.
// The last named mutable state value set determines the typestate
processor Lamp
  def colours: $;
  @Off: 0;
  state Off
    source switchOn
      @On: $@Off mod $colours::length + 1;
      'Shining a $colours($@On); light$#10;' !
    end switchOn
  end Off
  state On
    source turnOff
      @Off: $@On;
      'Lamp is off$#10;' !
    end turnOff
  end On
end Lamp

def myLamp: [colour#green, colour#blue] -> Lamp;

$myLamp::switchOn -> !OUT::write // Shining a green light
$myLamp::turnOff -> !OUT::write  // Lamp is off
$myLamp::switchOn -> !OUT::write // Shining a blue light
$myLamp::turnOff -> !OUT::write  // Lamp is off
$myLamp::switchOn -> !OUT::write // Shining a green light

// Use regular expressions to test strings
['banana', 'apple', 'pear', 'cherry']... -> \(
  when <'.*a.*'> do '$; contains an ''a''' !
  otherwise '$; has no ''a''' !
\) -> '$;
' -> !OUT::write

// Use composers with regular expressions and defined rules to parse strings
composer parse-stock-line
  {inventory-id: <INT> (<WS>), name: <'\w+'> (<WS>), currency: <'.{3}'>,
    unit-price: <INT> (<WS>?) <parts>?}
  rule parts: associated-parts: [<part>+]
  rule part: <'[A-Z]\d+'> (<=','>?)
end parse-stock-line

'705 gizmo EUR5 A67,G456,B32' -> parse-stock-line -> !OUT::write
// {associated-parts: [A67, G456, B32], currency: EUR,
//     inventory-id: 705, name: gizmo, unit-price: 5}
'
' -> !OUT::write

// Stream a string to split it into glyphs.
// A list can be indexed/sliced by an array of indexes
// Outputs ['h','e','l','l','o'], indexing arrays/lists starts at 1
['abcdefghijklmnopqrstuvwxyz'...] -> $([8,5,12,12,15]) -> !OUT::write
'
' -> !OUT::write

// We have used only raw strings above.
// Strings can have different types as determined by a tag.
// Comparing different types is an error, unless a wider type bound is set
// Type bound is given in ´´ and '' means any string value, tagged or raw
templates get-string-type
  when <´''´ '.*'> do '$; is a raw string' !
  when <´''´ id´'\d+'> do '$; is a numeric id string' !
  when <´''´ =id´'foo'> do 'id foo found' !
  when <´''´ id´'.*'> do '$; is an id' !
  when <´''´ name´'.+'> do '$; is a name' !
  otherwise '$; is not a name or id, nor a raw string' !
end get-string-type

[name´'Anna', 'foo', id´'789', city´'London', id´'xzgh', id´'foo']...
-> get-string-type -> '$;
' -> !OUT::write

// Numbers can be raw, tagged or have a unit of measure
// Type .. is any numeric value, tagged, measure or raw
templates get-number-type
  when <´..´ =inventory-id´86> do 'inventory-id 86 found' !
  when <´..´ inventory-id´100..> do '$; is an inventory-id >= 100' !
  when <´..´ inventory-id´0..|..inventory-id´0> do '$; is an inventory-id' !
  when <´..´ 0"m"..> do '$; is an m-measure >= 0"m"' !
  when <´..´ ..0|0..> do '$; is a raw number' !
  otherwise '$; is not a positive m-measure nor an inventory-id, nor raw' !
end get-number-type

[inventory-id´86, inventory-id´6, 78"m", 5"s", 99, inventory-id´654]...
-> get-number-type -> '$;
' -> !OUT::write

// Measures can be used in arithmetic, "1" is the scalar unit
// When mixing measures you have to cast to the result measure
4"m" + 6"m" * 3"1" -> ($ ~/ 2"s")"m/s" -> '$;
' -> !OUT::write

// Tagged identifiers must be made into raw numbers when used in arithmetic
// Then you can cast the result back to a tagged identifier if you like
inventory-id´300 -> inventory-id´($::raw + 1) -> get-number-type -> '$;
' -> !OUT::write

// Fields get auto-typed, tagging raw strings or numbers by default
// You cannot assign the wrong type to a field
def item: { inventory-id: 23, name: 'thingy', length: 12"m" };

'Field inventory-id $item.inventory-id -> get-number-type;
' -> !OUT::write
'Field name $item.name -> get-string-type;
' -> !OUT::write
'Field length $item.length -> get-number-type;
' -> !OUT::write

// You can define types and use as type-tests. This also defines a field.
// It would be an error to assign a non-standard plate to a standard-plate field
data standard-plate <'[A-Z]{3}[0-9]{3}'>

[['Audi', 'XYZ345'], ['BMW', 'I O U']]... -> \(
  when <?($(2) <standard-plate>)> do {make: $(1), standard-plate: $(2)}!
  otherwise {make: $(1), vanity-plate: $(2)}!
\) -> '$;
' -> !OUT::write

// You can define union types
data age <"years"|"months">

[ {name: 'Cesar', age: 20"years"},
  {name: 'Francesca', age: 19"years"},
  {name: 'Bobby', age: 11"months"}]...
-> \(
// Conditional tests on structures look a lot like literals, with field tests
  when <{age: <13"years"..19"years">}> do '$.name; is a teenager'!
  when <{age: <"months">}> do '$.name; is a baby'!
// You don't need to handle all cases, 'Cesar' will just be ignored
\) -> '$;
' -> !OUT::write

// Array/list indexes start at 1 by default, but you can choose
// Slices return whatever overlaps with the actual array
[1..5] -> $(-2..2) -> '$;
' -> !OUT::write // Outputs [1,2]
0:[1..5] -> $(-2..2) -> '$;
' -> !OUT::write // Outputs [1,2,3]
-2:[1..5] -> $(-2..2) -> '$;
' -> !OUT::write // Outputs [1,2,3,4,5]

// Arrays can have indexes of measures or tagged identifiers
def game-map: 0"y":[
  1..5 -> 0"x":[
    1..5 -> level´1:[
      1..3 -> {
        level: $,
        terrain-id: 6 -> SYS::randomInt,
        altitude: (10 -> SYS::randomInt)"m"
      }
    ]
  ]
];

// Projections (indexing) can span several dimensions
$game-map(3"y"; 1"x"..3"x"; level´1; altitude:) -> '$;
' -> !OUT::write // Gives a list of three altitude values

// Flatten and do a grouping projection to get stats
// Count and Max are built-in collector processors
[$game-map... ... ...] -> $(collect {
      occurences: Count,
      highest-on-level: Max&{by: :(altitude:), select: :(level:)}
    } by $({terrain-id:}))
-> !OUT::write
'
' -> !OUT::write

// Relations are sets of structures/records.
// Here we get all unique {level:, terrain-id:, altitude:} combinations
def location-types: {|$game-map... ... ...|};

// Projections can re-map structures. Note § is the relative accessor
$location-types({terrain-id:, foo: §.level::raw * §.altitude})
-> '$;
' -> !OUT::write

// Relational algebra operators can be used on relations
($location-types join {| {altitude: 3"m"} |})
-> !OUT::write
'
' -> !OUT::write

// Define your own operators for binary operations
operator (left dot right)
  $left -> \[i]($ * $right($i)!\)... -> ..=Sum&{of: :()} !
end dot

([1,2,3] dot [2,5,8]) -> 'dot product: $;
' -> !OUT::write

// Supply parameters to vary templates behaviour
templates die-rolls&{sides:}
  1..$ -> $sides::raw -> SYS::randomInt -> $ + 1 !
end die-rolls

[5 -> die-rolls&{sides:4}] -> '$;
' -> !OUT::write

// Pass templates as parameters, maybe with some parameters pre-filled
source damage-roll&{first:, second:, third:}
  (1 -> first) + (1 -> second) + (1 -> third) !
end damage-roll

$damage-roll&{first: die-rolls&{sides:4},
  second: die-rolls&{sides:6}, third: die-rolls&{sides:20}}
-> 'Damage done is $;
' -> !OUT::write

// Write tests inline. Run by --test flag on command line
// Note the ~ in the matcher means "not",
// and the array content matcher matches elements < 1 and > 4
test 'die-rolls'
  assert [100 -> die-rolls&{sides: 4}] <~[<..~1|4~..>]> 'all rolls 1..4'
end 'die-rolls'

// Provide modified modules to tests (aka test doubles or mocks)
// IN is the standard input object and ::lines gets all lines
source read-numbers
  $IN::lines -> #
  when <'\d+'> do $!
end read-numbers

test 'read numbers from input'
  use shadowed core-system/
    processor MockIn
      source lines
        [
          '12a',
          '65',
          'abc'
        ]... !
      end lines
    end MockIn
    def IN: $MockIn;
  end core-system/
  assert $read-numbers <=65> 'Only 65 is read'
end 'read numbers from input'

// You can work with byte arrays
composer hexToBytes
  <HEX>
end hexToBytes

'1a5c678d' -> hexToBytes -> ($ and [x 07 x]) -> $(last-1..last) -> '$;
' -> !OUT::write // Outputs 0005