Furcate

Macro preprocessor for JavaScript

Motivation

The C language has a macro preprocessor which allows programmers to inject xeno-language statements into their source code. This is useful because it allows a single code base to be used for two or more targets without having to rely on compile time or execution time conditionals.

The furcate utility provides a similar feature for JavaScript source code.

Prerequisites and installation

The furcate utility uses Node.js. Package installation is done via NPM. These are the only two prerequisites.

To install the utility and make it available to your Bash shell, use this command.

[user@host]# npm install -g furcate

Usage

The software is invoked from the command line with:

[user@host]# furcate [input-file] [output-file] --defs=definitions-file

The input file is a regular JavaScript source code file with:

• macro definitions
• macro affirmative conditionals
• macro negative conditionals
• macro substitutions
• comments

The definitions file contains the #define statements for evaluating which macro conditional statements to keep or discard.

The macro syntax adheres to the following EBNF.

definition        := '#define' defName defValue
defName           := [A-Z] | [a-z] | [0-9] | '$' |'-' | '_'
defValue          := boolean | unicode-text
boolean           := 0 | false | False | FALSE | 1 | true | True | TRUE

begin affirmative := '<<' defName
end affirmative   := defName '>>'
begin negative    := '<<!' defName
end negative      := '!' defName '>>'

substitution      := '<' defName '>'

terminal-comment  := '//' unicode-text
block-comment     := '/*' unicode-text '*/'

Here is an example that defines HELLO and uses it in a substitution:

#define HELLO Hola Mundo

function f(name) {
    console.log('<HELLO> ' + name);
}

Here is an example that defines PRO-VERSION and conditionally includes a block of code:

#define PRO-VERSION
<<PRO-VERSION
    var goldmine = new Bitcoin();
    goldmine.payday();
PRO-VERSION>>

Here is an example that defines FREE-VERSION and conditionally excludes a block of code:

#define FREE-VERSION
<<!FREE-VERSION
    var goldmine = new Bitcoin();
    goldmine.payday();
!FREE-VERSION>>
<<FREE-VERSION
    var poorman = new Chips();
    poorman.payday();
FREE-VERSION>>

License

The furcate command line utility is licensed under the MIT License.

Availability