Define function vs define action.

There is both a top level define method as well as a define action type. What is the difference between them? The method does accept a cost, otherwise they both accept a string and an expression. Let’s look at the implementations.

The top level define method declares a function that takes no args with the name of the value, and inserts the expression as the definition when calling it.

Whereas the other define, inserts into the locals table the expression.

In [22]: egraph.let("z", Lit(Int(1)))

In [23]: egraph.extract_expr(Var("z"))
Out[23]: (0, Lit(Int(1)), [])

In [24]: egraph.print_function("z", 10)
Out[24]: '(z) -> 1\n'

In [25]: egraph.eval_actions(Let("a", Lit(Int(1))))

In [26]: egraph.print_function("a", 10)
---------------------------------------------------------------------------
EggSmolError                              Traceback (most recent call last)
Cell In [26], line 1
----> 1 egraph.print_function("a", 10)

EggSmolError: Unbound symbol a

In [27]: egraph.extract_expr(Var("a"))
---------------------------------------------------------------------------
EggSmolError                              Traceback (most recent call last)
Cell In [27], line 1
----> 1 egraph.extract_expr(Var("a"))

EggSmolError: Errors:
Unbound symbol a

So how does one access a local variable?

How does egglog handle boolean values?   EGraphs in Python