3 ms·

It has the first class function objects, but not the lexical scoping. Try entering this and storing it into a variable: << -> x << << x >> >> >> If you r

It has the first class function objects, but not the lexical scoping. Try entering this and storing it into a variable: << -> x << << x >> >> >> If you run that object with something on the stack, you'll get this in return. 1: << x >> That x is a local variable reference, which makes it different than if you just entered this << x >> And if you evaluate it, it blows up with an error to that effect. (Since RPL doesn't really close over the lexical environment.) Years ago, I wrote a Scheme-based derivative of RPL that fixed some of this and found it rather fun to play around with.

chewzerita 7y ago
https://min-lang.org/learn-definitions/ https://min-lang.org/learn-definitions/ Min has lexical scoping too.
vcbdcgdg 7y ago
I have a question, if you don't mind: I have a stopwatch function in my HP48 that I don't want using a local variable (avoid polluting my precious menu), or having to keep it in a stack. Instead I want the value of the last time I ran the program to be stored within the program itself. I believe this is called a closure in CS. Right now I can have << value -> X 'expression' EVAL rest of the program >> And it'll work just fine, but how could I get the value at the very top modified? (I know my cell phone has a stopwatch. We're not allowed phones at work)
- mschaef 7y ago
  > I have a question, if you don't mind: Not at all. > I have a stopwatch function in my HP48 that I don't want using a local variable (avoid polluting my precious menu), or having to keep it in a stack. The first thing that comes to mind is that there's a hidden directory at the root that the ROM itself uses to store stuff like this. This link talks a bit about how to get there: https://www.hpmuseum.org/forum/thread-12986.html https://www.hpmuseum.org/forum/thread-12986.html This uses SYSEVAL to call into a normally-not-visible object that puts the name of the directory on the stack. From there, you should be able to read/write the variable. You may also be able to do some hacky stuff with self-modifying code, but that's honestly something I'd avoid unless you want to try it for fun.

chewzerita 7y ago

https://min-lang.org/learn-definitions/ https://min-lang.org/learn-definitions/ Min has lexical scoping too.

vcbdcgdg 7y ago

I have a question, if you don't mind: I have a stopwatch function in my HP48 that I don't want using a local variable (avoid polluting my precious menu), or having to keep it in a stack. Instead I want the value of the last time I ran the program to be stored within the program itself. I believe this is called a closure in CS. Right now I can have << value -> X 'expression' EVAL rest of the program >> And it'll work just fine, but how could I get the value at the very top modified? (I know my cell phone has a stopwatch. We're not allowed phones at work)

mschaef 7y ago
> I have a question, if you don't mind: Not at all. > I have a stopwatch function in my HP48 that I don't want using a local variable (avoid polluting my precious menu), or having to keep it in a stack. The first thing that comes to mind is that there's a hidden directory at the root that the ROM itself uses to store stuff like this. This link talks a bit about how to get there: https://www.hpmuseum.org/forum/thread-12986.html https://www.hpmuseum.org/forum/thread-12986.html This uses SYSEVAL to call into a normally-not-visible object that puts the name of the directory on the stack. From there, you should be able to read/write the variable. You may also be able to do some hacky stuff with self-modifying code, but that's honestly something I'd avoid unless you want to try it for fun.