Check out Modern Chess, our featured variant for January, 2025.

Enter Your Reply

The Comment You're Replying To
🕸Fergus Duniho wrote on Mon, May 25, 2020 12:46 PM UTC:

There are two ways of getting the value of a variable. One is to prepend the variable name with the # symbol. This works by replacing the #var_name with its value during preprocessing. This is useful for commands that do not provide any evaluation of expressions. It can be used on any line, regardless of the command.

The other way works only in expressions, and it is to precede the variable name with the keyword var. In some instances, it doesn't matter which you use. But in function definitions it does. Consider these lines of code: 

def test1 join "a" #v;
def test2 join "b" var v;
print fn test1;
print fn test2;
set v x;
def test3 join "c" #v;
print fn test1;
print fn test2;
print fn test3;
set v y;
print fn test1;
print fn test2;
print fn test3;

Here is their output:

a#v

b

a#v

bx

cx

a#v

by

cx

As you can tell from examining the output, the method of prepending a variable name with # works only when a function is defined, and it will insert the current value of that variable into the function definition without enabling the function to use the most recent value of the variable on subsequent function calls. But the var keyword will always retrieve the current value of the variable everytime the function is called. For this reason, it is important to use the var keyword in function definitions whenever there is any chance that its value may change. The preprocessing method of retrieving variable values may be used in a function definition only for variables that have already been set and will not change.

The same should apply to prepending constant names with @ or prepending system variables with $. You're probably okay prepending a constant name with @, because its value is not supposed to change. Some system variables change regularly, and some do not. For those that do change, it is better to use the system keyword to retrieve their value in function definitions.


Edit Form

Comment on the page Game Courier Developer's Guide

Conduct Guidelines
This is a Chess variants website, not a general forum.
Please limit your comments to Chess variants or the operation of this site.
Keep this website a safe space for Chess variant hobbyists of all stripes.
Because we want people to feel comfortable here no matter what their political or religious beliefs might be, we ask you to avoid discussing politics, religion, or other controversial subjects here. No matter how passionately you feel about any of these subjects, just take it someplace else.
Avoid Inflammatory Comments
If you are feeling anger, keep it to yourself until you calm down. Avoid insulting, blaming, or attacking someone you are angry with. Focus criticisms on ideas rather than people, and understand that criticisms of your ideas are not personal attacks and do not justify an inflammatory response.
Quick Markdown Guide

By default, new comments may be entered as Markdown, simple markup syntax designed to be readable and not look like markup. Comments stored as Markdown will be converted to HTML by Parsedown before displaying them. This follows the Github Flavored Markdown Spec with support for Markdown Extra. For a good overview of Markdown in general, check out the Markdown Guide. Here is a quick comparison of some commonly used Markdown with the rendered result:

Top level header: <H1>

Block quote

Second paragraph in block quote

First Paragraph of response. Italics, bold, and bold italics.

Second Paragraph after blank line. Here is some HTML code mixed in with the Markdown, and here is the same <U>HTML code</U> enclosed by backticks.

Secondary Header: <H2>

  • Unordered list item
  • Second unordered list item
  • New unordered list
    • Nested list item

Third Level header <H3>

  1. An ordered list item.
  2. A second ordered list item with the same number.
  3. A third ordered list item.
Here is some preformatted text.
  This line begins with some indentation.
    This begins with even more indentation.
And this line has no indentation.

Alt text for a graphic image

A definition list
A list of terms, each with one or more definitions following it.
An HTML construct using the tags <DL>, <DT> and <DD>.
A term
Its definition after a colon.
A second definition.
A third definition.
Another term following a blank line
The definition of that term.