Name Rascal/Expressions/Values/Location

Synopsis (Source code) location values.

Syntax | Uri | ( O, L, <BL, BC> , <EL,EC> ) where:

• Uri is an arbitrary Uniform Resource Identifier (URI).
• O and L are integer expressions giving the offset of this location to the begin of file, respectively, its length.
• BL and BC are integers expressions giving the begin line and begin column.
• EL and EC are integers expressions giving the end line and end column.

The part following the second pipe symbol (|) is optional.

Types loc

Details AddSegment Equal FieldSelection GreaterThan GreaterThanOrEqual LessThan LessThanOrEqual NotEqual

Description Location values are represented by the type loc and serve the following purposes:

• Providing a uniform mechanism for accessing local or remote files. This is used in all IO-related library functions.
• If the optional part is present they serve as text coordinates in a specific local or remote source file. This is very handy to associate a source code location which extracted facts.

URIs are explained in Uniform Resource Identifier. From their original definition in RFC3986 we cite the following useful overview of an URI:

         foo://example.com:8042/over/there?name=ferret#nose
         \_/   \______________/\_________/ \_________/ \__/
          |           |            |            |        |
       scheme     authority       path        query   fragment
          |   _____________________|__
         / \ /                        \
         urn:example:animal:ferret:nose

The elements of a location value can be accessed and modified using the standard mechanism of field selection and field assignment. The corresponding field names are:

• uri: the URI of the location. Also subfields of the URI can be accessed:
  • scheme: the scheme (or protocol) to be used.
  • authority: the domain where the data are located, as a str
  • host: the host where the URI is hosted (part of authority), as a str
  • port: port on host (part of authority), as a int
  • path: path name of file on host, as a str
  • extension: file name extension, as a str
  • query: query data, as a str
  • fragment: the fragment name following the path name and query data, as a str
  • user: user info (only present in schemes like mailto), as a str
  • parent : removes the last segment from the path component, if any, as a loc
  • file : the last segment of the path, as a str
  • ls : the contents of a directory, if the loc is a directory, as a list[loc]
• offset: start of text area.
• length: length of text area
• begin.line, begin.column: begin line and column of text area.
• end.line, end.column end line and column of text area.

Supported protocols are:

Scheme name and pattern	Description
http://host:port/path?query#fragment	access a remote file via the web.
file:///path	access a local file on the file system.
cwd:///path	access the current working directory (the directory from which Rascal was started).
home:///path	access the home directory of the user.
std:///path	access the Rascal standard library.
tmp:///path	access the temporay file directory.
jar:url!/[entry]	access any entry in a zip file (or a jar)
rascal://qualifiedModulename	access the source code of a Rascal module name
project://projectName/projectRelativePath	access a project in the current instance of Eclipse.
bundleresource://bundleId/bundleRelativePath	access OSGI bundles. Only active in Eclipse context

Examples Locations with specific position information should always be generated automatically but for the curious here is an example:

rascal>|file:///home/paulk/pico.trm|(0,1,<2,3>,<4,5>)
loc: |file:///home/paulk/pico.trm|(0,1,<2,3>,<4,5>)

Note that this is equivalent to using the home scheme:

rascal>|home://pico.trm|(0,1,<2,3>,<4,5>)
loc: |home://pico.trm|(0,1,<2,3>,<4,5>)

Accessing a file src/HelloWorld.java in a project with the name example-project in the currently running Eclipse is done as follows:

rascal>|project://example-project/src/HelloWorld.java|
loc: |project://example-project/src/HelloWorld.java|

You could read a webpage:

rascal>import IO;
ok
rascal>println(readFile(|http://www.example.org|))
<!doctype html>
<html>
<head>
    <title>Example Domain</title>

    <meta charset="utf-8" />
    <meta http-equiv="Content-type" content="text/html; charset=utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <style type="text/css">
    body {
        background-color: #f0f0f2;
        margin: 0;
        padding: 0;
        font-family: "Open Sans", "Helvetica Neue", Helvetica, Arial, sans-serif;
        
    }
    div {
        width: 600px;
        margin: 5em auto;
        padding: 50px;
        background-color: #fff;
        border-radius: 1em;
    }
    a:link, a:visited {
        color: #38488f;
        text-decoration: none;
    }
    @media (max-width: 700px) {
        body {
            background-color: #fff;
        }
        div {
            width: auto;
            margin: 0 auto;
            border-radius: 0;
            padding: 1em;
        }
    }
    </style>    
</head>

<body>
<div>
    <h1>Example Domain</h1>
    <p>This domain is established to be used for illustrative examples in documents. You may use this
    domain in examples without prior coordination or asking for permission.</p>
    <p><a href="http://www.iana.org/domains/example">More information...</a></p>
</div>
</body>
</html>

ok

Addition on locations creates longer paths:

rascal>x = |tmp://myTempDirectory|;
loc: |tmp://myTempDirectory|
rascal>x += "myTempFile.txt";
loc: |tmp://myTempDirectory/myTempFile.txt|

Check the contents of a folder:

rascal>|project://example-project/src|.ls
list[loc]: [
  |project://example-project/src/Apple.java|,
  |project://example-project/src/Fruit.java|,
  |project://example-project/src/HelloWorld.java|,
  |project://example-project/src/IFruit.java|
]

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