Poly/ML January 2026

polyml@lists.polyml.org

9 participants
6 discussions

Type Constraints and Overloading
by Duke Normandin 02 Mar '26

02 Mar '26

Taken from Paulson's book: Chap2.4 A) fun square x = x * x; > Error- Unable to resolve overloading for * I understand the above! B) fun square(x : real) = x * x; I understand: x is declared as a real C) fun square x = x * x : real; I see this as declaring a function w/o parentheses AND that the r_result_ is a 'real' I have a problem with this declaration: D) fun square x : real = x * x; I see this as declaring a function w/o parentheses, AND declaring x to be a 'real' I do NOT see/understand that this syntax indicates that the type of the _result_ is a 'real' I suppose that I'm free to ignore D) and use the more IMHO intuitive C) declaration. I thought that I'd ask to make sure that I wasn't missing something in the D) one. TIA .... -- Duke

6 12

variable shadowing
by Duke Normandin 25 Jan '26

25 Jan '26

I think that I almost understand "shadowing", maybe ... val pi = 3.14159; fun area (r) = pi*r*r; area 2.0; => 12.56636 So far so good ... re-declare pi ... val p1 = 0.0; Here is where things get blurry for me. When/how is the *new* pi available? Is it only available if re-declared in a *block* of code, making it local to that block and therefore usable there and only there? After re-declaring pi above, executing the "area" function uses the original pi. I get that! What I'm not sure of is how to use the re-declared pi. TIA ... -- Duke

2 2

"symbolic" identifier names
by Duke Normandin 21 Jan '26

21 Jan '26

Reading Paulson!! Right ON!! lol [quote] ML also permits symbolic names. These consist of the characters ! % & $ # + - * / : < = > ? @ \ ˜ ‘ ˆ | Names made up of these characters can be as long as you like: ----> $ˆ$ˆ$ˆ$ !!?@**??!! :-|==>-># Certain strings of special characters are reserved for ML’s syntax and should not be used as symbolic names: : | = => -> # :> A symbolic name is allowed wherever an alphabetic name is: val +-+-+ = 1415; > val +-+-+ = 1415 : int [/quote] What purpose would this cryptic-tude serve? Obfuscation? Seeding brain cancer? What? Or do most of you simply ignore this allowance? Enjoying Paulson!! And so far, Poly&Paulson are a team!! :) -- Duke

2 2

Type error in function application
by Duke Normandin 21 Jan '26

21 Jan '26

This function: fun divide (x: real, y: real) = if y = 0.0 then raise DivByZero 5 else x / y; is taken from: "Beginner's Guide to Standard ML" It's part of a "calculator" program included in the document. I'm using: $ poly --use ./calc.sml Poly/ML 5.9.2 Release and it chokes and quits at line 4 on the above function. I made no typo! So! What now? Why doesn't Poly/ML not like that code? TIA ... -- Duke

5 8

First step woes
by Duke Normandin 18 Jan '26

18 Jan '26

From: INTRODUCTION TO POLY D.C.J. Matthews,May 1982 Computer Laboratory, University of Cambridge [quote] > begin # print("Hello"); # print(" again") # end; Hello again [/quote] but I get: [quote] > begin # print("hello"); poly: : error: Value or constructor (begin) has not been declared Found near begin print ("hello") Static Errors > [/quote] if I remove the semi-colon, it lets me enter the rest of the code, but chokes after I enter `end;'. Has the syntax changed since the book was written, or am I doing something wrong? TIA ... -- Duke

3 3

Defining a function
by Duke Normandin 18 Jan '26

18 Jan '26

Noob to SML & PolyML here! Trying to solve "exercism" SML track. Lesson2 wants me to create a function as: fun leapyear blah blah I have a bunch of pdf docs for sml-nj, poly/ml etc and none show that syntax to create a function. What am I missing? TIA ... -- Duke

2 3

2026

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

Poly/ML January 2026