ToothyGDL/Language

• Introduction
  
• Notes
  
• Game Logic Syntax
  
• Notes on Implementation
  

Introduction

• A set of declarations for all required game state.
  
• A set of (conditional, ordered list of text strings and integer expressions, set of state assignments)
  

• Initialise the game state
  
• Repeat
  
  • Clear set of permitted actions
    
  • Evaluate all conditionals in the world. For all those that are true,
    
    • Evaluate the integer expressions/text strings to create an action label
      
    • Add (a mapping from this label to the set of state assignments) to the set of permitted actions
      
  • Allow the user to select one of the available actions
    
  • Execute the attached state assignments for the selected action
    

Notes

• Operator precedence is currently as follows (operators grouped together have equal precedence): - (^, &, |, %), (*, /), (+, -), (==, !=, <, >, <=, >=), (and,  or) - thanks to PeterTaylor
  
• If the runtime engine tries to resolve the symbol "random" and that symbol has not been otherwise defined, the engine will return a random integer x in the range 0 <= x < 2 if resolving the symbol as an integer, and 0 <= x < index if resolving as an array. This functionality is not enabled at initialisation time, and attempting to use it then will produce a compiler error.
  
• The for loops do not behave quite as they do in languages like C/C++; it's more like PostScript?'s repeat operation. In particular, the range is cached on entry and not reevaluated, so assignments to range variables in the loop body will not affect the number of iterations; and also the loop variable is local within the loop body and recreated for each iteration, so assignments to it do not affect the progress of the loop. These properties, together with the fact that there is no other way to cause code to loop, should ensure that each code block always terminates (though it might take a long time to do so); implying that the language is *not* Turing-complete, unless you consider the user to be part of the system.
  
• If a game complains about version mismatches, try refreshing the page first - your browser may be caching an old version of the engine files. Only recompile if that fails.
  
• The engine can save and load the state of the game to the user's cookie. To trigger this ability, define an integer called _save_slot. Whenever its value is zero or greater, the save option will appear, and the load option will also appear if cookie data exists under the right name; different cookie parameter names will be generated for different values. This allows the game writer to supply the player with multiple game slots if they so choose, and also to control times during the game during which the player can/cannot save. The cookie name depends on the set of global variable names, so the engine does not attempt to load saved states if the game code expects to be able to resolve a different set of globals to those stored in the state.
  

Game Logic Syntax

 optional-qualifier int identifier { integer expression }
 optional-qualifier array identifier { comma-separated list of integer expressions }

 for identifier ( minimum .. maximum ) { list of game rule declarations }

 when { boolean expression } allow { list of semicolon-terminated assignments } label { list of string expressions }

 lvalue assignment-operator integer expression

 + - / * %

 stringtable identifier { comma-separated list of whitespace-separated lists of string expressions }

 newline

 box { list of formatting commands }

 width { css }
 height { css }
 border { css }
 margin { css }
 padding { css }
 background { css }
 position { list of position-related css }
 content { list of string expressions, which may include string table lookups }
 bind_action { list of string expressions, which may include string table lookups }
 while_active { list of formatting commands }

• position type - absolute, relative, fixed.. etc.
  
• left: (integer expression) css length unit
  
• top: (integer expression) css length unit
  

 sprite { list of formatting commands }

 repeatedly { list of string expressions }

Optimisation tips

• JS string operations are slow. If you can get away without content for your display elements, do.
  
• If using repeatedly, try to arrange your interface so you can make all elements that will change often into sprites.
  

Notes on Implementation