Chef

Introduction

Chef is a programming language in which programs look like recipes.

NEW: Additional syntax specifications added 17 July, 2003, marked in red. Fixed spelling of "liquefy" keyword.

Design Principles

Program recipes should not only generate valid output, but be easy to prepare and delicious.
Recipes may appeal to cooks with different budgets.
Recipes will be metric, but may use traditional cooking measures such as cups and tablespoons.

Language Concepts

Ingredients

All recipes have ingredients! The ingredients hold individual data values. All ingredients are numerical, though they can be interpreted as Unicode for I/O purposes. Liquid ingredients will be output as Unicode characters, while dry or unspecified ingredients will be output as numbers.

Mixing Bowls and Baking Dishes

Chef has access to an unlimited supply of mixing bowls and baking dishes. These can contain ingredient values. The ingredients in a mixing bowl or baking dish are ordered, like a stack of pancakes. New ingredients are placed on top, and if values are removed they are removed from the top. Note that if the value of an ingredient changes, the value in the mixing bowl or baking dish does not. The values in the mixing bowls and baking dishes also retain their dry or liquid designations.

Multiple mixing bowls and baking dishes are referred to by an ordinal identifier - "the 2nd mixing bowl". If no identifier is used, the recipe only has one of the relevant utensil. Ordinal identifiers must be digits followed by "st", "nd", "rd" or "th", not words.

Syntax Elements

The following items appear in a Chef recipe. Some are optional. Items must appear in the order shown below, with a blank line (two newlines) between each item.

Recipe Title

The recipe title describes in a few words what the program does. For example: "Hello World Souffle", or "Fibonacci Numbers with Caramel Sauce". The recipe title is always the first line of a Chef recipe, and is followed by a full stop.

recipe-title.

Comments

Comments are placed in a free-form paragraph after the recipe title. Comments are optional.

Ingredient List

The next item in a Chef recipe is the ingredient list. This lists the ingredients to be used by the program. The syntax is

Ingredients.
[initial-value] [[measure-type] measure] ingredient-name
[further ingredients]

Ingredients are listed one per line. The intial-value is a number, and is optional. Attempting to use an ingredient without a defined value is a run-time error. The optional measure can be any of the following:

g | kg | pinch[es] : These always indicate dry measures.
ml | l | dash[es] : These always indicate liquid measures.
cup[s] | teaspoon[s] | tablespoon[s] : These indicate measures which may be either dry or liquid.

The optional measure-type may be any of the following:

heaped | level : These indicate that the measure is dry.

The ingredient-name may be anything reasonable, and may include space characters. The ingredient list is optional. If present, it declares ingredients with the given initial values and measures.

Cooking Time

Cooking time: time (hour[s] | minute[s]).

The cooking time statement is optional. The time is a number.

Oven Temperature

Pre-heat oven to temperature degrees Celcius [(gas mark mark)].

Some recipes require baking. If so, there will be an oven temperature statement. This is optional. The temperature and mark are numbers.

Method

Method.
method statements

The method contains the actual recipe instructions. These are written in sentences. Line breaks are ignored in the method of a recipe. Valid method instructions are:

Take ingredient from refrigerator.
This reads a numeric value from STDIN into the ingredient named, overwriting any previous value.
Put ingredient into [nth] mixing bowl.
This puts the ingredient into the nth mixing bowl.
Fold ingredient into [nth] mixing bowl.
This removes the top value from the nth mixing bowl and places it in the ingredient.
Add ingredient [to [nth] mixing bowl].
This adds the value of ingredient to the value of the ingredient on top of the nth mixing bowl and stores the result in the nth mixing bowl.
Remove ingredient [from [nth] mixing bowl].
This subtracts the value of ingredient from the value of the ingredient on top of the nth mixing bowl and stores the result in the nth mixing bowl.
Combine ingredient [into [nth] mixing bowl].
This multiplies the value of ingredient by the value of the ingredient on top of the nth mixing bowl and stores the result in the nth mixing bowl.
Divide ingredient [into [nth] mixing bowl].
This divides the value of ingredient into the value of the ingredient on top of the nth mixing bowl and stores the result in the nth mixing bowl.
Add dry ingredients [to [nth] mixing bowl].
This adds the values of all the dry ingredients together and places the result into the nth mixing bowl.
Liquefy | Liquify ingredient.
This turns the ingredient into a liquid, i.e. a Unicode character for output purposes. (Note: The original specification used the word "Liquify", which is a spelling error. "Liquify" is deprecated. Use "Liquefy" in all new code.)
Liquefy | Liquify contents of the [nth] mixing bowl.
This turns all the ingredients in the nth mixing bowl into a liquid, i.e. a Unicode characters for output purposes.
Stir [the [nth] mixing bowl] for number minutes.
This "rolls" the top number ingredients in the nth mixing bowl, such that the top ingredient goes down that number of ingredients and all ingredients above it rise one place. If there are not that many ingredients in the bowl, the top ingredient goes to tbe bottom of the bowl and all the others rise one place.
Stir ingredient into the [nth] mixing bowl.
This rolls the number of ingredients in the nth mixing bowl equal to the value of ingredient, such that the top ingredient goes down that number of ingredients and all ingredients above it rise one place. If there are not that many ingredients in the bowl, the top ingredient goes to tbe bottom of the bowl and all the others rise one place.
Mix [the [nth] mixing bowl] well.
This randomises the order of the ingredients in the nth mixing bowl.
Clean [nth] mixing bowl.
This removes all the ingredients from the nth mixing bowl.
Pour contents of the [nth] mixing bowl into the [pth] baking dish.
This copies all the ingredients from the nth mixing bowl to the pth baking dish, retaining the order and putting them on top of anything already in the baking dish.
Verb the ingredient.
This marks the beginning of a loop. It must appear as a matched pair with the following statement. The loop executes as follows: The value of ingredient is checked. If it is non-zero, the body of the loop executes until it reaches the "until" statement. The value of ingredient is rechecked. If it is non-zero, the loop executes again. If at any check the value of ingredient is zero, the loop exits and execution continues at the statement after the "until". Loops may be nested.
Verb [the ingredient] until verbed.
This marks the end of a loop. It must appear as a matched pair with the above statement. verbed must match the Verb in the matching loop start statement. The Verb in this statement may be arbitrary and is ignored. If the ingredient appears in this statement, its value is decremented by 1 when this statement executes. The ingredient does not have to match the ingredient in the matching loop start statement.
Set aside.
This causes execution of the innermost loop in which it occurs to end immediately and execution to continue at the statement after the "until".
Serve with auxiliary-recipe.
This invokes a sous-chef to immediately prepare the named auxiliary-recipe. The calling chef waits until the sous-chef is finished before continuing. See the section on auxiliary recipes below.
Refrigerate [for number hours].
This causes execution of the recipe in which it appears to end immediately. If in an auxiliary recipe, the auxiliary recipe ends and the sous-chef's first mixing bowl is passed back to the calling chef as normal. If a number of hours is specified, the recipe will print out its first number baking dishes (see the Serves statement below) before ending.

Serves

The final statement in a Chef recipe is a statement of how many people it serves.

Serves number-of-diners.

This statement writes to STDOUT the contents of the first number-of-diners baking dishes. It begins with the 1st baking dish, removing values from the top one by one and printing them until the dish is empty, then progresses to the next dish, until all the dishes have been printed. The serves statement is optional, but is required if the recipe is to output anything!

Auxiliary Recipes

These are small recipes which are needed to produce specialised ingredients for the main recipe (such as sauces). They are listed after the main recipe. Auxiliary recipes are made by sous-chefs, so they have their own set of mixing bowls and baking dishes which the head Chef never sees, but take copies of all the mixing bowls and baking dishes currently in use by the calling chef when they are called upon. When the auxiliary recipe is finished, the ingredients in its first mixing bowl are placed in the same order into the calling chef's first mixing bowl.

For example, the main recipe calls for a sauce at some point. The sauce recipe is begun by the sous-chef with an exact copy of all the calling chef's mixing bowls and baking dishes. Changes to these bowls and dishes do not affect the calling chef's bowls and dishes. When the sous-chef is finished, he passes his first mixing bowl back to the calling chef, who empties it into his first mixing bowl.

An auxiliary recipe may have all the same items as a main recipe.

Sample Recipes

Chef on the Net

Chef was featured in Round Two of the 2002 MIT Mystery Hunt!
Steffen Müller has written a Chef interpeter perl module.
Chef was assigned for a student project in the LCC 2700 Introduction to Computational Media course at the Georgia Institute of Technology, Fall 2005 semester.