the inputs to a function; the expressions for each argument follow the function name


a type of data with two values: true and false


using a function by giving it inputs


messages in the code, generally ignored by the computer, to help people interacting with the code understand what it is doing


a function that creates instances of a data structure


a statement of the name, domain, and range of a function

contract error

errors where the code makes sense, but uses a function with the wrong number or type of arguments

data block

code that lists the name, constructor(s), and field(s) of a data structure

data structure

a 'container' data type, which has fields that can hold other data (e.g. - a 'coordinate' is a data structure holding number fields x and y)

data type

a way of classifying values, such as: Number, String, Image, Boolean, or any user-defined data structure


to associate a descriptive name with a value

definitions area

the left-most text box in the Editor where definitions for values and functions are written


the type or set of inputs that a function expects

dot accessor

a way to extract the values of fields an instance


software in which code can be written and evaluated

error message

information from the computer about errors in code


something that happens outside of a running program, which the program can respond to


shows the use of a function on specific inputs and the computation the function should perform on those inputs


a part of a data structure that has a name and holds a single value of a specified data type


a relation from a set of inputs to a set of possible outputs, where each input is related to exactly one output

function definition

code that names a function, lists its variables, and states the expression to compute when the function is used


Connects an event (like a tick or keypress) and a function within a reactor

helper function

a small function that handles a specific part of another computation, and gets called from other functions


the side opposite the 90-degree angle in a right triangle


a type of data for pictures


a specific example of a data structure, with specific values for each field (e.g. - (4,5) is an instance of an (x,y) coordinate

interactions area

the right-most text box in the Editor, where expressions are entered to be evaluated


how we refer to a function or value defined in a language (examples: +, *, star, circle)


a symbol that manipulates two Numbers and produces a result


the point (0,0) where the horizontal and vertical axes intersect

piecewise function

a function that computes different expressions based on its input

purpose statement

a concise, detailed description of what a function does with its inputs


the type or set of outputs that a function produces


the relative sizes of two or more values


a value that contains a current state, and functions for updating, drawing, and interacting with that state


the process of changing the style or structure of a program’s code, without changing the program’s behavior


resize an image to be larger or smaller while maintaining ratios and proportions


the value of a changing system at any point in time (i.e. a stoplight can be in the 'red', 'yellow' or 'green' state). In Pyret, the state of a Reactor is it’s current value.

syntax error

errors where the computer cannot make sense of the code (e.g. - missing commas, missing parentheses, unclosed strings)


a specific piece of data, like 5 or "hello"


a name or symbol that stands for some value or expression, often a value or expression that changes