Preferences

Preferences

The Scheme preference pages are used to configure various aspects of the Scheme editor and it's integration with a Scheme interpreter.

Scheme - main page
Appearance
Comments
External Interpreter
Fast Eval Keys
Indentation
Lexical Extensions
Remote Interpreter
Syntax

Scheme - main page

This page controls the tab size width, and allows the serialization of a subset of the preferences, namely those relating to syntax and indentation (those that are usually shared between members of a development team).

Appearance

The Appearance page controls the appearance of the various tokens in a Scheme source file, as well as the background color, and the way matching parentheses are highlighted.

Comments

The Comments page are used to customize comment-related features:

• the comment prefix inserted when lines are commented out;
• the author name and copyright added to header comments (inserted by the Scheme file header comment command);
• a flag indicating whether hitting Enter in a comment makes the comment continue on the next line.

External Interpreter

The External Interpreter preference page is used to configure an external Scheme interpreter with which the Scheme editor interacts (as opposed to the embedded Kawa interpreter).

To set up a Scheme interpreter, you must minimally provide:

• the interpreter's name,
• the command line to start the interpreter, and
• the directory where the interpreter is started.

The specification of the working directory can include variables, as described here.

Also, you can specify a regular expression that will be matched against all lines in the console window to detect error messages with their corresponding file name and line number (the location of the error). Simply enter a valid (Java) regular expression in the field named Error Regexp, taking care to have a group that matches the filename, another group that matches the line number, and a third group that matches the part of the line that should be highlighted as an hyperlink.

Here are a few configurations for some Scheme interpreters:

Interpreter	Error Regexp	Filename	Line	Link
MzScheme (with errortrace)	((([a-z]:)?[^:]+):([0-9]+):[0-9]+): .*	2	4	1
Kawa	[\t ]+at [^(]+\(((.+):([0-9]+))\)	2	3	1

Note that with Kawa, files must be loaded by giving their full path name.

Fast Eval Keys

You can configure the Fast Eval keys using the Fast Eval preference page:

Indentation

Indentation is a crucial part of a Scheme editor. The Indentation page controls how sub-expressions are indented. To be easily readable by others, Scheme code indentation must obey strict, standard rules.

The page shows a three column table, with some controls above it to add/remove entries in the table. Each entry corresponds to a Scheme symbol and tells the editor how to indent expressions directly inside S-expressions starting with this symbol.

The columns in the table are:

• Name
- the symbol;
• Indentation scheme - tells how sub-expressions are indented. The possible values are:
  • default - all sub-expressions are indented below the first symbol of the enclosing expression;
  • definition - all sub-expressions are indented as the enclosing expression plus 2 spaces (like most defining forms).
  • if - all sub-expressions are indented as the enclosing expression plus 4 spaces (like an if special form).
  • sequence - all sub-expressions are indented as the enclosing expression plus 2 spaces (like in a begin special form).
  • with - this is the most complex and general scheme. It is used to control the proper indentation of calls to functions like with-input-from-file, for example. Thus it's name. In such function calls, the first N parameters are indented of 4 spaces, while the others are indented of 2 spaces. This number, N, is called the hint, and is specified in the third column.
  • none - no indentation at all, all sub-expressions are indented at the same level as the enclosing expression (this is quite unusual in Scheme, but can be used to circumvent the indentation of top-level definitions in PLT-style modules).
• Hint - when the indentation scheme is set to with, this number controls how many sub-expressions are indented of 4 spaces.

Lexical extensions

Lexical extensions are flags that can be set to change how some tokens are processed in the Scheme source file.

These flags are:

• Treat brackets as parentheses - some Scheme systems treat square brackets as parentheses (PLT Scheme, SISC, etc), some don't (e.g. Kawa). Use this flag to ensure correct parsing and proper parenthesis matching.
• Accept dash as identifier part - some Scheme systems allow dashes as part of identifier. Use this flag to ensure correct parsing.

Remote Interpreter

The Remote Interpreter page is used to set the hostname and the port number to be used to connect to a remote interpreter.

Syntax

The Syntax page is used to categorize symbols. These categories are used when coloring the various symbols in a source file. Symbols not appearing in any of these lists are colored using the default color and attributes.

A regular expression can also be used to assign symbols to the various categories. The regular expression must be entered in the text field below the list box.

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