Best afterFunctions: package an idea you can call

Parameters: order matters

When you call a function, the arguments fill its parameters by position, left to right. Get the order wrong and the function computes something else entirely — here, a negative amount of money 'left'. Watch the call stack bind the parameters.

We have a budget of 100 and have spent 30. Work out how much is left (we want 70).

Arguments in the wrong order execution-derived · CPython

variables

state after line 1 runs· pass 1 of 2

variable	value
`remaining`	`<function remaining>`coerced

step 1 / 5

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What you are looking at

Watch the function's frame open: which parameter gets which value?

Buggy — remaining(30, 100) binds budget = 30 and spent = 100 by position, so it returns 30 - 100 = -70. The arguments went in backwards.
Procedural — remaining(budget=100, spent=30) names each argument, so they land on the right parameters regardless of order, and left is the 70 we wanted.

Every state you see came from running the program under CPython's tracer at build time — see how GlassBox stays honest.