Crate slac

The Simple Logic & Arithmetic Compiler is a library to convert an single expression statement into a structured Expression abstract syntax tree.

The AST can be validated, (de)serialized, and executed using the built-in interpreter.

Example

use slac::{check_variables_and_functions, compile, execute, StaticEnvironment, Value};
use slac::stdlib::extend_environment;

let ast = compile("max(10, 20) + 1").expect("compiles the ast");
let mut env = StaticEnvironment::default();

extend_environment(&mut env);
check_variables_and_functions(&env, &ast).expect("find the usage of max");

let result = execute(&env, &ast).expect("execute the expression");
assert_eq!(Value::Number(21.0), result);

Serialization / Deserialization

The Expression can be fully serialized into an (e.g.) JSON string for precompilation and cached execution using serde. See test/serde_test.rs for the resulting JSON.

Modules

• environment
  Dynamic variables and function calls can be provided by an Environment.
• optimizer
  Transformation routines to optimize an Expression AST.
• stdlib
  The SLAC standard library features various functions which can be included into a StaticEnvironment.

Structs

• Compiler
  A compiler to transform a list of Tokens into a single nested Expression tree.
• Scanner
  A lexer to split a string into a list of Tokens.
• StaticEnvironment
  An Environment implementation in which all variables and functions are known ahead of execution. All variable and function names treated as case-insensitive.

Enums

• Error
  The error type for failures while scanning, compiling or validation slac expressions.
• Expression
  An Expression is a statement which can always be evaluated to a single Value. A recursive Expression is the foundation of an AST.
• Operator
  A binary or arithemtic operator.
• Token
  A Token is the smallest logical unit evaluated by the compiler.
• Value
  A Wrapper for the four different possible variable types.

Functions

• check_boolean_result
  Checks if the top level Expression produces a Value::Boolean result.
• check_variables_and_functions
  Validates Variable and Call Expressions by walking the AST and returning the first error.
• compile
  Compiles a string into an Expression tree.
• execute
  Executes an Expression using an Environment.
• optimize
  Transforms an Expression tree by applying transform_ternary and fold_constants in a loop until no further optimization is possible.

Type Aliases

• Result
  A specialized Result type for Errors during the scanning, compiling or validation phase.