[−][src]Crate zia
Interpreter for the Zia programming language
The Zia project aims to develop a programming language that can be used to program itself.
Instead of storing the source code as plain text and editing the raw text (which can easily break
the program), the runtime environment of the interpreter (the Context
) can be saved to disk and
used in other programs. All the programming is done using an interactive shell such as
IZia. The commands sent are
interpreted based on the Context
. They are used to incrementally modify, test and debug the Context
.
Expressions for Zia commands represent a binary tree where parentheses group a pair of expressions
and a space separates a pair of expressions. For example "(ll lr) (rl rr)"
represents a perfect
binary tree of height 2 with leaves "ll"
, "lr"
, "rl"
, "rr"
going from left to right.
The leaves of the tree can be any unicode string without spaces or parentheses. These symbols may be recognised by the intepreter as concepts or if not used to label new concepts.
Currently, only the lowest-level functionality has been implemented. It's important that programs
are represented consistently and transparently within the Context
in order to achieve a
self-describing system. The syntax shown below may appear awkward but more convenient syntax will
be possible once more functionality is added. For example, the need to group pairs of expressions
in parentheses will be alleviated by functionality to set the relative precedence and associativity
of concepts.
So far there are 4 built-in concepts. A new Context
labels these with the symbols, "label_of"
,
"->"
, ":="
, "let"
, but the labels can be changed to different symbols (e.g. for different
languages or disciplines).
Examples
extern crate zia; use zia::{Context, ContextMaker, Execute, ZiaError}; // Construct a new `Context` using the `new` method of the `ContextMaker` trait let mut context = Context::new(); // Specify the rule that the concept "a b" reduces to concept "c" assert_eq!(context.execute("let ((a b) (-> c))"), ""); assert_eq!(context.execute("a b"), "c"); // Change the rule so that concept "a b" instead reduces to concept "d" assert_eq!(context.execute("let ((a b) (-> d))"), ""); assert_eq!(context.execute("a b"), "d"); // Change the rule so "a b" doesn't reduce any further assert_eq!(context.execute("let ((a b) (-> (a b)))"), ""); assert_eq!(context.execute("a b"), "a b"); // Try to specify a rule that already exists assert_eq!(context.execute("let ((a b) (-> (a b)))"), ZiaError::RedundantReduction.to_string()); assert_eq!(context.execute("let ((a b) (-> c))"), ""); assert_eq!(context.execute("let ((a b) (-> c))"), ZiaError::RedundantReduction.to_string()); // Relabel "label_of" to "표시" assert_eq!(context.execute("let (표시 (:= label_of))"), ""); assert_eq!(context.execute("표시 (a b)"), "\'c\'"); // Try to specify the rule to reduce a labelled concept assert_eq!(context.execute("let (a (-> d))"), ZiaError::MultipleReductionPaths.to_string()); // Try to specify the composition of a concept in terms of itself assert_eq!(context.execute("let (b (:= (a b)))"), ZiaError::InfiniteDefinition.to_string()); // Try to specify the reduction of concept in terms of itself assert_eq!(context.execute("let ((c d) (-> ((c d) e))"), ZiaError::ExpandingReduction.to_string());
Structs
SyntaxTree | Represents syntax as a full binary tree and links syntax to concepts where possible. |
Enums
ZiaError | All the expected ways a Zia command could be invalid. |
Traits
Call | Calling a program expressed as a syntax tree to read or write contained concepts. |
ContextMaker | Preparing a context by labelling concrete concepts. |
Definer | Defining new syntax in terms of old syntax. |
Execute | Executing a command based on a string to add, write, read, or remove contained concepts. |
Type Definitions
Context | A container for adding, writing, reading and removing |