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RPN calculator implementations in 61 languages

85 points by nkurz 8y ago

AstroJetson 8y ago
I love things like this. While 99 bottles of beer is pretty simple, applications like this give you a slightly better look at the language. I try doing a simple 4 function calculator (*/+-) with parens and with two numerical addins (sometimes I pick sin/cos, sometimes I pick max( ....) and min( ...) The RPN version is good since you need to create stack management in the core. While this doesn't have the panache of "Write a web server in 3 lines of Ruby (oh don't forget those two 500 line libraries.) It does give you good example of the simple things you can do. He also has a pretty good swath of languages, I'm always excited to see Awk, Lua and Python (my go to lanaguages) on the same page. I'll need to see if I can break out my COBOL skills and get a pull request made up.
bytematic 8y ago
This is really cool, I think I would like to do this as an exercise with a similar small program. Does he have some sort of write-up after making all these talking about the individual languages?
mhh__ 8y ago
The D version currently on display on the website (Which I wrote, minus the use of static foreach): void main() { import std.stdio, std.string, std.algorithm, std.conv; // Reduce the RPN expression using a stack readln.split.fold!((stack, op) { switch (op) { // Generate operator switch cases statically static foreach (c; "+-*/") case [c]: return stack[0 .. $ - 2] ~ mixin("stack[$ - 2] " ~ c ~ " stack[$ - 1]"); default: return stack ~ op.to!real; } })((real[]).init).writeln; }
janci 8y ago
I expected the javascript implementation to be a oneliner with Array reduce operation.
- bastawhiz 8y ago
  I was very disappointed that the JS implementation leans on eval(). That's kind of cheating, no?
Scott_Sanderson 8y ago
Love using RPN
dajonker 8y ago
Related code golf challenge: https://codegolf.stackexchange.com/questions/221/reverse-polish-notation https://codegolf.stackexchange.com/questions/221/reverse-pol...
passed_By 8y ago
So, haskell version may be little shorter main = interact $ unlines. map (show.calc) .lines calc :: String -> [Float] calc = foldl f [] . words where f (x:y:zs) "+" = (y + x):zs f (x:y:zs) "-" = (y - x):zs f (x:y:zs) "*" = (y * x):zs f (x:y:zs) "/" = (y / x):zs f xs y = read y : xs

85 points by nkurz 8y ago

I love things like this. While 99 bottles of beer is pretty simple, applications like this give you a slightly better look at the language. I try doing a simple 4 function calculator (*/+-) with parens and with two numerical addins (sometimes I pick sin/cos, sometimes I pick max( ....) and min( ...) The RPN version is good since you need to create stack management in the core. While this doesn't have the panache of "Write a web server in 3 lines of Ruby (oh don't forget those two 500 line libraries.) It does give you good example of the simple things you can do. He also has a pretty good swath of languages, I'm always excited to see Awk, Lua and Python (my go to lanaguages) on the same page. I'll need to see if I can break out my COBOL skills and get a pull request made up.

bytematic 8y ago

This is really cool, I think I would like to do this as an exercise with a similar small program. Does he have some sort of write-up after making all these talking about the individual languages?

mhh__ 8y ago

The D version currently on display on the website (Which I wrote, minus the use of static foreach): void main() { import std.stdio, std.string, std.algorithm, std.conv; // Reduce the RPN expression using a stack readln.split.fold!((stack, op) { switch (op) { // Generate operator switch cases statically static foreach (c; "+-*/") case [c]: return stack[0 .. $ - 2] ~ mixin("stack[$ - 2] " ~ c ~ " stack[$ - 1]"); default: return stack ~ op.to!real; } })((real[]).init).writeln; }

janci 8y ago

I expected the javascript implementation to be a oneliner with Array reduce operation.

bastawhiz 8y ago
I was very disappointed that the JS implementation leans on eval(). That's kind of cheating, no?

Scott_Sanderson 8y ago

Love using RPN

dajonker 8y ago

Related code golf challenge: https://codegolf.stackexchange.com/questions/221/reverse-polish-notation https://codegolf.stackexchange.com/questions/221/reverse-pol...

passed_By 8y ago

So, haskell version may be little shorter main = interact $ unlines. map (show.calc) .lines calc :: String -> [Float] calc = foldl f [] . words where f (x:y:zs) "+" = (y + x):zs f (x:y:zs) "-" = (y - x):zs f (x:y:zs) "*" = (y * x):zs f (x:y:zs) "/" = (y / x):zs f xs y = read y : xs