This use case is nicely covered by short form for keyword arguments. So in this
case instead of plot(x, z), we'd have plot(=x, =z) which would be transformed
into plot(**{'x': x, 'z': z}) at compile time. This could work for any
expression:
foo(=lamda x: x*2) -> foo(**{'lamda x: x*2': lamda x: x*2})
This feature is easy to implement and has broad applications.
> On 13 Jul 2019, at 21:16, Nima Hamidi <[email protected]> wrote:
>
> Hello all,
>
> I would like to briefly share my thoughts on non-standard evaluation (NSE),
> why this is useful, and how, potentially, it can be added to Python. In most
> languages, functions have access only to the value of their arguments, and
> not to the expressions that yielded those values. However, sometimes it is
> useful to have access to the expressions as well. For example, let plot(x, y,
> ...) be a function that draws the scatter plot of y against x and adds labels
> for the x- and y-axes. Currently, there is no way to distinguish plot(x, z,
> ...) from plot(x, y, ...) from within the function. As such, one needs to
> pass the names of the variables to the plot function to be used as the axes'
> labels. Using NSE, though, the function can look at the expressions in the
> method call and use those as the default value for labels. In R, this idea is
> used widely to make the syntax simpler.
>
> In the following, I sketch how I think this can be implemented:
> Let BoundExpression be a class containing an ast.Expression as well as locals
> and globals dictionaries. BoundExpression can also have an eval method that
> evaluates its expression using its locals and globals dictionaries.
> Let `x` be the short form for BoundExpression("x", locals(), globals()).
> Then, the plot function can be implemented in a way that plot(`x`, `y`) draws
> scatter plot of x and y and also, labels the axes correctly. No need to
> provide labels explicitly anymore.
> A more challenging idea is to let developers decide whether their functions
> need NSE or not. For example, when a function is defined as def f(`x`), for
> any method call like f(x), the first argument should be wrapped with a
> BoundExpression instance.
> I would appreciate any feedback on these ideas.
>
> Best,
> Nima
>
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