How to install
haxelib git hscript-improved https://github.com/Redar13/hscript-improved.git
To enable custom classes support you have to do this in project.xml
<define name="CUSTOM_CLASSES" />
Parse and evalutate Haxe expressions.
In some projects it's sometimes useful to be able to interpret some code dynamically, without recompilation.
Haxe script is a complete subset of the Haxe language.
It is dynamically typed but allows all Haxe expressions apart from type (class,enum,typedef) declarations.
var expr = "var x = 4; 1 + 2 * x";
var parser = new hscript.Parser();
var ast = parser.parseString(expr);
var interp = new hscript.Interp();
trace(interp.execute(ast));
In case of a parsing error an hscript.Expr.Error
is thrown. You can use parser.line
to check the line number.
You can set some globaly accessible identifiers by using interp.variables.set("name",value)
Here's a small example of Haxe Script usage :
var script = "
var sum = 0;
for( a in angles )
sum += Math.cos(a);
sum;
";
var parser = new hscript.Parser();
var program = parser.parseString(script);
var interp = new hscript.Interp();
interp.variables.set("Math",Math); // share the Math class
interp.variables.set("angles",[0,1,2,3]); // set the angles list
trace( interp.execute(program) );
This will calculate the sum of the cosines of the angles given as input.
Haxe Script has not been really optimized, and it's not meant to be very fast. But it's entirely crossplatform since it's pure Haxe code (it doesn't use any platform-specific API).
When compiled with -D hscriptPos
you will get fine error reporting at parsing time.
You can subclass hscript.Interp
to override behaviors for get
, set
, call
, fcall
and cnew
.
You can add more binary and unary operations to the parser by setting opPriority
, opRightAssoc
and unops
content.
You can use parser.allowJSON
to allow JSON data.
You can use parser.allowTypes
to parse types for local vars, exceptions, function args and return types. Types are ignored by the interpreter.
You can use parser.allowMetadata
to parse metadata before expressions on in anonymous types. Metadata are ignored by the interpreter.
You can use new hscript.Macro(pos).convert(ast)
to convert an hscript AST to a Haxe macros one.
You can use hscript.Checker
in order to type check and even get completion, using haxe -xml
output for type information.
Compared to Haxe, limitations are :
switch
construct is supported but not pattern matching (no variable capture, we use strict equality to comparecase
values andswitch
value)- only one variable declaration is allowed in
var
- the parser supports optional types for
var
andfunction
ifallowTypes
is set, but the interpreter ignores them - you can enable per-expression position tracking by compiling with
-D hscriptPos
- you can parse some type declarations (import, class, typedef, etc.) with parseModule
In order to install Haxe Script, use haxelib install hscript
and compile your program with -lib hscript
.
These are the main required files in hscript :
hscript.Expr
: contains enums declarationshscript.Parser
: a small parser that turns a string into an expression structure (AST)hscript.Interp
: a small interpreter that execute the AST and returns the latest evaluated value
Some other optional files :
hscript.Async
: converts Expr into asynchronous versionhscript.Bytes
: Expr serializer/unserializerhscript.Checker
: type checking and completion for hscript Exprhscript.Macro
: convert Haxe macro into hscript Exprhscript.Printer
: convert hscript Expr to Stringhscript.Tools
: utility functions (map/iter)