Syntax: Meta-Programming Helpers
9 Source Locations
On this page:
9.1Representations
source-location?
source-location-list?
source-location-vector?
check-source-location!
build-source-location
build-source-location-list
build-source-location-vector
build-source-location-syntax
source-location-known?
source-location-source
source-location-line
source-location-column
source-location-position
source-location-span
source-location-end
update-source-location
source-location->string
source-location->prefix
9.2Source Location Utilities
syntax-source-directory
syntax-source-file-name
9.2.1Quoting
quote-srcloc
quote-source-file
quote-line-number
quote-column-number
quote-character-position
quote-character-span
quote-srcloc-string
quote-srcloc-prefix
quote-module-name
quote-module-path
8.18
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9Source LocationsπŸ”— i

Carl Eastlund <cce@ccs.neu.edu>

There are two libraries in this collection for dealing with source locations; one for manipulating representations of them, and the other for quoting the location of a particular piece of source code.

9.1RepresentationsπŸ”— i

(require syntax/srcloc ) package: base

This module defines utilities for manipulating representations of source locations, including both srcloc structures and all the values accepted by datum->syntax ’s third argument: syntax objects, lists, vectors, and #f.

These functions recognize valid source location representations. The first, source-location? , recognizes srcloc structures, syntax objects, lists, and vectors with appropriate structure, as well as #f. The latter predicates recognize only valid lists and vectors, respectively.

Examples:
> (source-location? #f)

#t

> (source-location? #'here)

#t

> (source-location? (make-srcloc 'here1010))

#t

> (source-location? (make-srcloc 'bad1#f10))

#f

> (source-location? (list 'here1010))

#t

> (source-location? (list* 'bad1010'tail))

#f

> (source-location? (vector 'here1010))

#t

> (source-location? (vector 'bad0000))

#f

procedure

( check-source-location! namex)→void?

name:symbol?
x:any/c
This procedure checks that its input is a valid source location. If it is, the procedure returns (void ). If it is not, check-source-location! raises a detailed error message in terms of name and the problem with x.

Examples:
> (check-source-location! 'this-example#f)
> (check-source-location! 'this-example#'here)
> (check-source-location! 'this-example(make-srcloc 'here1010))
> (check-source-location! 'this-example(make-srcloc 'bad1#f10))

this-example: expected a source location with line number

and column number both numeric or both #f; got 1 and #f

respectively: (srcloc 'bad 1 #f 1 0)

> (check-source-location! 'this-example(list 'here1010))
> (check-source-location! 'this-example(list* 'bad1010'tail))

this-example: expected a source location (a list of 5

elements); got an improper list: '(bad 1 0 1 0 . tail)

> (check-source-location! 'this-example(vector 'here1010))
> (check-source-location! 'this-example(vector 'bad0000))

this-example: expected a source location with a positive

line number or #f (second element); got line number 0:

'#(bad 0 0 0 0)

These procedures combine multiple (zero or more) source locations, merging locations within the same source and reporting #f for locations that span sources. They also convert the result to the desired representation: srcloc , list, vector, or syntax object, respectively.

Examples:
> (build-source-location )

(srcloc #f #f #f #f #f)

> (build-source-location-list )

'(#f #f #f #f #f)

> (build-source-location-vector )

'#(#f #f #f #f #f)

> (build-source-location-syntax )

#<syntax ()>

> (build-source-location #f)

(srcloc #f #f #f #f #f)

> (build-source-location-list #f)

'(#f #f #f #f #f)

> (build-source-location-vector #f)

'#(#f #f #f #f #f)

> (build-source-location-syntax #f)

#<syntax ()>

> (build-source-location (list 'here1234))

(srcloc 'here 1 2 3 4)

> (build-source-location-list (make-srcloc 'here1234))

'(here 1 2 3 4)

> (build-source-location-vector (make-srcloc 'here1234))

'#(here 1 2 3 4)

> (build-source-location-syntax (make-srcloc 'here1234))

#<syntax:here:1:2 ()>

> (build-source-location (list 'here1234)(vector 'here5678))

(srcloc 'here 1 2 3 12)

> (build-source-location-list (make-srcloc 'here1234)(vector 'here5678))

'(here 1 2 3 12)

> (build-source-location-vector (make-srcloc 'here1234)(vector 'here5678))

'#(here 1 2 3 12)

> (build-source-location-syntax (make-srcloc 'here1234)(vector 'here5678))

#<syntax:here:1:2 ()>

> (build-source-location (list 'here1234)(vector 'there5678))

(srcloc #f #f #f #f #f)

> (build-source-location-list (make-srcloc 'here1234)(vector 'there5678))

'(#f #f #f #f #f)

> (build-source-location-vector (make-srcloc 'here1234)(vector 'there5678))

'#(#f #f #f #f #f)

> (build-source-location-syntax (make-srcloc 'here1234)(vector 'there5678))

#<syntax ()>

This predicate reports whether a given source location contains more information than simply #f.

Examples:
> (source-location-known? #f)

#f

> (source-location-known? (make-srcloc #f#f#f#f#f))

#f

> (source-location-known? (make-srcloc 'source1234))

#t

> (source-location-known? (list #f#f#f#f#f))

#f

> (source-location-known? (vector 'source#f#f#f#f))

#t

> (source-location-known? (datum->syntax #fnull #f))

#f

> (source-location-known? (datum->syntax #fnull (list 'source#f#f#f#f)))

#t

These accessors extract the fields of a source location.

Examples:
> (source-location-source #f)

#f

> (source-location-line (make-srcloc 'source1234))

1

> (source-location-column (list 'source1234))

2

> (source-location-position (vector 'source1234))

3

> (source-location-span (datum->syntax #fnull (list 'source1234)))

4

This accessor produces the end position of a source location (the sum of its position and span, if both are numbers) or #f.

Examples:
> (source-location-end #f)

#f

> (source-location-end (make-srcloc 'source1234))

7

> (source-location-end (list 'source123#f))

#f

> (source-location-end (vector 'source12#f4))

#f

procedure

( update-source-location loc
#:sourcesource
#:lineline
#:columncolumn
#:positionposition
#:spanspan) → source-location?
loc:source-location?
source:any/c
line:(or/c exact-nonnegative-integer? #f)
column:(or/c exact-positive-integer? #f)
position:(or/c exact-nonnegative-integer? #f)
span:(or/c exact-positive-integer? #f)
Produces a modified version of loc, replacing its fields with source, line, column, position, and/or span, if given.

Examples:
> (update-source-location #f#:source'here)

'(here #f #f #f #f)

> (update-source-location (list 'there1234)#:line20#:column79)

'(there 20 79 3 4)

> (update-source-location (vector 'everywhere1234)#:position#f#:span#f)

'#(everywhere 1 2 #f #f)

These procedures convert source locations to strings for use in error messages. The first produces a string describing the source location; the second appends ": " to the string if it is non-empty.

Examples:
> (source-location->string (make-srcloc 'here1234))

"here:1:2"

> (source-location->string (make-srcloc 'here#f#f34))

"here::3-7"

> (source-location->string (make-srcloc 'here#f#f#f#f))

"here"

> (source-location->string (make-srcloc #f1234))

":1:2"

> (source-location->string (make-srcloc #f#f#f34))

"::3-7"

> (source-location->string (make-srcloc #f#f#f#f#f))

""

> (source-location->prefix (make-srcloc 'here1234))

"here:1:2: "

> (source-location->prefix (make-srcloc 'here#f#f34))

"here::3-7: "

> (source-location->prefix (make-srcloc 'here#f#f#f#f))

"here: "

> (source-location->prefix (make-srcloc #f1234))

":1:2: "

> (source-location->prefix (make-srcloc #f#f#f34))

"::3-7: "

> (source-location->prefix (make-srcloc #f#f#f#f#f))

""

Changed in version 8.1.0.5 of package base: Changed format to separate a line and column with : instead of .

9.2Source Location UtilitiesπŸ”— i

(require syntax/location ) package: base

procedure

( syntax-source-directory stx)→(or/c path? #f)

stx:syntax?

procedure

( syntax-source-file-name stx)→(or/c path? #f)

stx:syntax?
These produce the directory and file name, respectively, of the path with which stx is associated, or #f if stx is not associated with a path.

Examples:
(define loc
(list (build-path "/tmp""dir""somewhere.rkt")
#f#f#f#f))
(define stx1(datum->syntax #f'somewhereloc))
> (syntax-source-directory stx1)

#<path:/tmp/dir/>

> (syntax-source-file-name stx1)

#<path:somewhere.rkt>

(define stx2(datum->syntax #f'nowhere#f))
> (syntax-source-directory stx2)

#f

> (syntax-source-directory stx2)

#f

Added in version 6.3 of package base.

9.2.1QuotingπŸ”— i

The following macros evaluate to various aspects of their own source location.

Note: The examples below illustrate the use of these macros and the representation of their output. However, due to the mechanism by which they are generated, each example is considered a single character and thus does not have realistic line, column, and character positions.

Furthermore, the examples illustrate the use of source location quoting inside macros, and the difference between quoting the source location of the macro definition itself and quoting the source location of the macro’s arguments.

syntax

( quote-srcloc )

(quote-srcloc form)
(quote-srcloc form#:module-sourceexpr)
Quotes the source location of form as a srcloc structure, using the location of the whole (quote-srcloc ) expression if no expr is given. Uses relative directories for paths found within the collections tree, the user’s collections directory, or the PLaneT cache.

Examples:
> (quote-srcloc )

(srcloc 'eval 2 0 2 1)

> (define-syntax (not-herestx)#'(quote-srcloc ))
> (not-here)

(srcloc 'eval 3 0 3 1)

> (not-here)

(srcloc 'eval 3 0 3 1)

> (define-syntax (herestx)#`(quote-srcloc #,stx))
> (here)

(srcloc 'eval 7 0 7 1)

> (here)

(srcloc 'eval 8 0 8 1)

You can achieve an effect similar to __FILE__ from Perl or Ruby and __file__ from Python by using quote-source-file .

Quote various fields of the source location of form, or of the whole macro application if no form is given.

Examples:
> (list (quote-source-file )
(quote-line-number )
(quote-column-number )
(quote-character-position )
(quote-character-span ))

'(eval 2 0 2 1)

> (define-syntax (not-herestx)
#'(list (quote-source-file )
(quote-line-number )
(quote-column-number )
(quote-character-position )
(quote-character-span )))
> (not-here)

'(eval 3 0 3 1)

> (not-here)

'(eval 3 0 3 1)

> (define-syntax (herestx)
#`(list (quote-source-file #,stx)
(quote-line-number #,stx)
(quote-column-number #,stx)
(quote-character-position #,stx)
(quote-character-span #,stx)))
> (here)

'(eval 7 0 7 1)

> (here)

'(eval 8 0 8 1)

Quote the result of source-location->string or source-location->prefix , respectively, applied to the source location of form, or of the whole macro application if no form is given.

Examples:
> (list (quote-srcloc-string )
(quote-srcloc-prefix ))

'("eval:2:0" "eval:2:0: ")

> (define-syntax (not-herestx)
#'(list (quote-srcloc-string )
(quote-srcloc-prefix )))
> (not-here)

'("eval:3:0" "eval:3:0: ")

> (not-here)

'("eval:3:0" "eval:3:0: ")

> (define-syntax (herestx)
#`(list (quote-srcloc-string #,stx)
(quote-srcloc-prefix #,stx)))
> (here)

'("eval:7:0" "eval:7:0: ")

> (here)

'("eval:8:0" "eval:8:0: ")

syntax

( quote-module-name submod-path-element...)

Quotes the name of the module in a form suitable for printing, but not necessarily as a valid module path. See quote-module-path for constructing quoted module paths.

Returns a path, symbol, list, or 'top-level, where 'top-level is produced when used outside of a module. A list corresponds to a submodule in the same format as the result of variable-reference->module-name. Any given submod-path-elements (as in a submod form) are added to form a result submodule path.

To produce a name suitable for use in printed messages, apply path->relative-string/library when the result is a path.

Examples:
> (module Aracket
(require syntax/location)
(define-syntax-rule (name)(quote-module-name ))
(define a-name(name))
(module+ C
(require syntax/location)
(define c-name(quote-module-name ))
(define c-name2(quote-module-name ".."))
(provide c-namec-name2))
(provide (all-defined-out )))
> (require 'A)
> a-name

'A

> (require (submod 'AC))
> c-name

'(A C)

> c-name2

'(A C "..")

> (module Bracket
(require syntax/location)
(require 'A)
(define b-name(name))
(provide (all-defined-out )))
> (require 'B)
> b-name

'B

> (quote-module-name )

'top-level

> (current-namespace (module->namespace ''A))
> (quote-module-name )

'A

syntax

( quote-module-path submod-path-element...)

Quotes the name of the module in which the form is compiled. When possible, the result is a valid module path suitable for use by dynamic-require and similar functions.

Builds the result using quote , a path, submod , or 'top-level, where 'top-level is produced when used outside of a module. Any given submod-path-elements (as in a submod form) are added to form a result submodule path.

Examples:
> (module Aracket
(require syntax/location)
(define-syntax-rule (path)(quote-module-path ))
(define a-path(path))
(module+ C
(require syntax/location)
(define c-path(quote-module-path ))
(define c-path2(quote-module-path ".."))
(provide c-pathc-path2))
(provide (all-defined-out )))
> (require 'A)
> a-path

''A

> (require (submod 'AC))
> c-path

'(submod 'A C)

> c-path2

'(submod 'A C "..")

> (module Bracket
(require syntax/location)
(require 'A)
(define b-path(path))
(provide (all-defined-out )))
> (require 'B)
> b-path

''B

> (quote-module-path )

'top-level

> (current-namespace (module->namespace ''A))
> (quote-module-path )

''A

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