Moving to Hugo.

1 files changed, 402 insertions, 0 deletions

diff --git a/content/learn/10.conditions/default.md b/content/learn/10.conditions/default.md
new file mode 100644
index 0000000..8a4f339
--- /dev/null
+++ b/content/learn/10.conditions/default.md
@@ -0,0 +1,402 @@
+---
+menuTitle: Conditionals
+title: "Expressing Conditions"
+weight: 10
+---
+In [the previous step](/learn/lambdas), we added lambda functions, which made
+it possible to store computation descriptions for later use. The `smithy.fate`
+is still a mess, and we couldn't handle the hero not having enough money for a
+purchase. Let's add conditions to our story.
+
+Fate has quite a few conditional constructs. `if_else`, `switch`, and `cond`
+can be used both as instruction and computation. `if` is only for instructions.
+* `if_else` selects between two options according to a given `bool` value.
+* `switch` has a list of options, each of which is associated to a value.
+   It selects the first listed option whose value is equal to the targeted
+   value. When used as a computation, a default option with no associated value
+   must be provided.
+* `cond` has a list of options, each of which is associated to a `bool`
+  computation. The first listed option for which the computation yields `(true)`
+  is chosen. In the case of a computation, the last option is chosen even as a
+  default value. With instructions, if no option has its condition satisfied,
+  nothing happens.
+* `if` is only for instructions, and applies its content only if the condition
+  is verified.
+
+All of these can be used within a `player_choice` to control what options are
+available.
+
+**smithy.fate:**
+
+         (fate_version 1)
+
+         (require smithy_inventory.fate)
+
+         (global (lambda text ((cons weapon int))) get_weapon_offer_label)
+         (global (lambda text ((cons armor int))) get_armor_offer_label)
+
+         (set get_weapon_offer_label
+            (lambda
+               ( ((cons weapon int) offer) )
+               (let
+                  (
+                     (weapon (car offer))
+                     (price (cdr offer))
+                  )
+                  (text
+                     Buy "(var weapon.name)" \(attack: (var weapon.attack),
+                     precision: (var weapon.precision)\) for (var price) coins.
+                  )
+               )
+            )
+         )
+
+         (set get_armor_offer_label
+            (lambda
+               ( ((cons armor int) offer) )
+               (let
+                  (
+                     (armor (car offer))
+                     (price (cdr offer))
+                  )
+                  (text
+                     Buy "(var armor.name)" \(defense: (var armor.defense)\),
+                     for (var price) coins.
+                  )
+               )
+            )
+         )
+
+         (global bool has_visited_smithy)
+
+         (set has_visited_smithy (false))
+
+         (define_sequence visit_smithy ()
+            (if (not (var has_visited_smithy))
+               As you approach the smithy, you notice that no one's there. All
+               the wares are out for selling. It's almost as if this story
+               didn't need more examples of lengthy dialogues.
+               (newline)
+               (set has_visited_smithy (true))
+            )
+            You have (var hero.money) coins.
+            (newline)
+            What will you look at?
+            (player_choice
+               (
+                  ( Let's see the weapons )
+                  (jump_to see_weapons)
+               )
+               (
+                  ( Let's see the armors )
+                  (jump_to see_armors)
+               )
+               (
+                  ( Nothing, let's go back to the bar )
+               )
+            )
+         )
+
+         (define_sequence see_weapons ()
+            ;; Still can be improved.
+            (player_choice
+               (
+                  ( (eval get_weapon_offer_label (access smithy_weapons 0)) )
+                  (visit buy_weapon (access smithy_weapons 0))
+                  (jump_to visit_smithy)
+               )
+               (
+                  ( (eval get_weapon_offer_label (access smithy_weapons 1)) )
+                  (visit buy_weapon (access smithy_weapons 1))
+                  (jump_to visit_smithy)
+               )
+               (
+                  ( Nevermind )
+                  (jump_to visit_smithy)
+               )
+            )
+         )
+
+         (define_sequence see_armors ()
+            ;; Still can be improved.
+            (player_choice
+               (
+                  ( (eval get_armor_offer_label (access smithy_armors 0)) )
+                  (visit buy_armor (access smithy_armors 0))
+                  (jump_to visit_smithy)
+               )
+               (
+                  ( (eval get_armor_offer_label (access smithy_armors 1)) )
+                  (visit buy_armor (access smithy_armors 1))
+                  (jump_to visit_smithy)
+               )
+               (
+                  ( Nevermind )
+                  (jump_to visit_smithy)
+               )
+            )
+         )
+
+         (define_sequence buy_weapon ( ((cons weapon int) weapon) )
+            ;; We can't even deny a sell yet...
+            (local int money_after)
+
+            (set money_after (- (var hero.money) (cdr weapon)))
+
+            (if_else (< (var money_after) 0)
+               (
+                  You can't afford that.
+                  (newline)
+                  You would need (abs (var money_after)) more coins.
+               )
+               (
+                  (set hero.weapon (car weapon))
+                  (set hero.money (var money_after))
+                  Equipped (var hero.weapon.name).
+               )
+            )
+            (newline)
+         )
+
+         (define_sequence buy_armor ( ((cons armor int) armor) )
+            ;; We can't even deny a sell yet...
+            (local int money_after)
+
+            (set money_after (- (var hero.money) (cdr armor)))
+
+            (if_else (< (var money_after) 0)
+               (
+                  You can't afford that.
+                  (newline)
+                  You would need (abs (var money_after)) more coins.
+               )
+               (
+                  (set hero.armor (car armor))
+                  (set hero.money (var money_after))
+                  Equipped (var hero.armor.name).
+               )
+            )
+            (newline)
+         )
+
+
+This was a first step toward cleaning up `smithy.fate`. Next, we'll use
+[conditions](/learn/conditions) to improve things further.
+
+----
+
+## Unchanged Files
+
+**data.fate:**
+
+         (fate_version 1)
+
+         (declare_structure weapon
+            (text name)
+            (int attack)
+            (int precision)
+         )
+
+         (declare_structure armor
+            (text name)
+            (int defense)
+         )
+
+         (declare_structure character
+            (string name)
+            (int money)
+            (weapon weapon)
+            (armor armor)
+         )
+
+         (global character hero)
+
+         (set_fields! hero.weapon
+            (name (text "Legendary" sword))
+            (attack 3)
+            (precision 50)
+         )
+
+         (set_fields! hero.armor
+            (name (text "Refined" attire))
+            (defense 1)
+         )
+
+         (set hero.money 42)
+
+**get_a_refill.fate:**
+
+         (fate_version 1)
+
+         (require data.fate)
+         (require actions.fate)
+
+         (define_sequence lower_price_of_booze
+            (
+               ((ptr int) price_pointer)
+               (int decrease)
+            )
+            Great! The price of booze just lowered from (at price_pointer)
+            (set (at price_pointer)
+               (-
+                  (at price_pointer)
+                  (var decrease)
+               )
+            )
+            to (at price_pointer)!
+         )
+
+         (define_sequence get_a_refill ()
+            (local int price_of_booze)
+
+            (set price_of_booze 12)
+
+            Staring straight at the barman, you raise your glass and proclaim:
+            (newline)
+            "This soon-to-be world savior needs more booze!"
+            (newline)
+            The barman's lack of reaction is disappointing, but seeing the beer
+            being poured does help improve the mood.
+            (newline)
+            Satisfied, you hand the barman (var price_of_booze) copper coins.
+            (visit pay (var price_of_booze))
+            (newline)
+            The barman sighs, then asks:
+            (prompt_string (ptr hero.name) 2 64 What is your name, then, hero?)
+            (var hero.name)?
+            (newline)
+            The barman looks surprised.
+            (newline)
+            (visit lower_price_of_booze (ptr price_of_booze) 4)
+            (newline)
+            "I have heard of you, (var hero.name)," the barman exclaims, "I have
+            a quest for you!"
+            (newline)
+            It's your turn to sigh.
+            (newline)
+            The barman hands you a bag, and says:
+            (newline)
+            "Take this pre-payment and head to the smithy."
+            (newline)
+         )
+
+**actions.fate:**
+
+         (fate_version 1)
+
+         (require data.fate)
+
+         (define_sequence pay ( (int cost) )
+            (set hero_money
+               (- (var hero.money) (var cost))
+            )
+         )
+
+**falling_asleep.fate:**
+
+         (fate_version 1)
+
+         (require data.fate)
+
+         (define_sequence fall_asleep ()
+            Deciding to break away from the expected storyline, you promptly
+            fall asleep.
+            (newline)
+            ...
+            (newline)
+            Upon waking up, your hard-trained reflexes inform you that someone
+            stole all your money.
+            (set hero.money 0)
+            (newline)
+            This set-back was more than you could take. You give up on this
+            barely coherent story.
+            (end)
+         )
+
+**main.fate:**
+
+         (fate_version 1)
+
+         Once upon a time, starting a story with these words wasn't considered
+         a cliche. Starting in a tavern might also not be seen as very
+         original.  Having the main character be an street orphan, raised by
+         some mysterious sage all to end up as a mercenary with an uncommonly
+         strong sense of honor probably isn't going to lead to any praises for
+         novelty either. Maybe you should drink to that.
+         (newline)
+         Or maybe you shouldn't. This isn't your first mug. Not your second
+         either.  Drinking to forget that you are a stereotypical hero isn't
+         going to solve anything. Worse, the alcoholic trait is part of the
+         image.
+         (newline)
+         As you contemplate your own pointless description, your gaze leaves
+         what turns out to be an already empty glass in your hand and finds the
+         barman.
+
+         (player_choice
+            (
+               ( Ask the barman for a refill )
+               (visit get_a_refill)
+            )
+            (
+               ( Fall asleep )
+               (jump_to fall_asleep)
+            )
+         )
+
+         (require get_a_refill.fate)
+         (require falling_asleep.fate)
+
+         (end)
+
+**smithy_inventory.fate:**
+         (fate_version 1)
+
+         (require data.fate)
+
+         (global (list (cons weapon int)) smithy_weapons)
+         (global (list (cons weapon int)) smithy_armors)
+
+         (add!
+            (cons
+               (set_fields (default weapon)
+                  (name (text An Iron Rod))
+                  (attack 10)
+                  (precision 70)
+               )
+               176
+            )
+            smithy_weapons
+         )
+         (add!
+            (cons
+               (set_fields (default weapon)
+                  (name (text A Magnificient Brick))
+                  (attack 6)
+                  (precision 90)
+               )
+               110
+            )
+            smithy_weapons
+         )
+
+         (add!
+            (cons
+               (set_fields (default armor)
+                  (name (text A raincoat?!))
+                  (defense 7)
+               )
+               160
+            )
+            smithy_armors
+         )
+         (add!
+            (cons
+               (set_fields (default armor)
+                  (name (text A nice cape))
+                  (defense 3)
+               )
+               50
+            )
+            smithy_armors
+         )