Serializing a function definition

[dpnova]

Hello! I couldn't find anything in the docs for this, if I wanted to serialize a user's function and make it available in other places they are using mathjs I think I'd have to store the line as a string and recompile it each time I load the calculation.

in one place:

let source1 = `
z=1
foo(x,y)=x+y
bar=foo(1,2)
`;
let scope = {};
math.evaluate(source1, scope);
serializeScope(scope)

then somewhere else (eg different web request) I would love this to work:

let otherSource = 'aval=foo(1,2)'
let scope = loadScope(..);
math.evaluate(otherSource, scope)

Do i have the right understanding here?

[josdejong]

That is an interesting case. When serializing (see docs), only data types can be serialized, and not functions. JavaScript functions can have bindings from outside, which would break when serializing. So it's not trivial to restore such a function. Also functions created inside the expression parser itself do have bindings.

A pragmatic solution for now could be to create a wrapper around the function evaluate, remember all expressions passed to evaluate, and simply store the orginal expressions. To restore this, all expressions can be executed again.

Fo the long term: a solution could be to extend functions created in the exprssion parser with a method .toJSON into something like {"mathjs":"Function","fn":"foo(x,y)=x+y"}, and creating a reviver to restore such a function by just evaluating its expression again.

[dpnova]

FTR our goal would be to make functions defined in a block like this available elsewhere in the same page (another mathjs block)

[josdejong]

Yes exactly! Makes a lot of sense

[josdejong]

I just had a look into this. When serializing functions created in the expression parser we have the same problem as with JavaScript functions: they can be bound to variables, so they cannot be deserialized on their own.

What I've done now is implement support for serialization in the Parser, see #3525. Will this address your concern @dpnova?

[dpnova]

@josdejong

Oh wow thanks mate!

Just heading to bed now but I'll have a look in the morning. This is still very much on our radar...

[josdejong]

PR #3525 is published now in v14.7.0