6.1.4 Symbols

Symbols are case sensitive and the reader is case sensitive too. So:

(eq? 'foo 'FOO) ⇒ #f
(eq? (string->symbol "foo") (string->symbol "FOO")) ⇒ #f

Symbols may contain special characters (such as #\Newline or #\Space). Such symbols that have to be read must be written: |[^]+|. The function write uses that notation when it encounters symbols containing special characters.

(write 'foo) ⇒ foo
(write 'Foo) ⇒Foo
(write '|foo bar|) ⇒ |foo bar|

procedure: symbol? obj

procedure: symbol->string symbol

Returns the name of the symbol as a string. Modifying the string result of symbol->string could yield incoherent programs. It is better to copy the string before any physical update. For instance, don’t write:

(string-downcase! (symbol->string 'foo))

See (R5RS)r5rs.info, for more details.

but prefer:

(string-downcase (symbol->string 'foo))

procedure: string->symbol string

bigloo procedure: string->symbol-ci string

bigloo procedure: symbol-append symbol …

String->symbol returns a symbol whose name is string. String->symbol respects the case of string. String->symbol-ci returns a symbol whose name is (string-upcase string). Symbol-append returns a symbol whose name is the concatenation of all the symbol’s names.

bigloo procedure: gensym [obj]

Returns a new fresh symbol. If obj is provided and is a string or a symbol, it is used as prefix for the new symbol.

bigloo procedure: genuuid

Returns a string containing a new fresh Universal Unique Identifier (see http://fr.wikipedia.org/wiki/Universal_Unique_Identifier).

bigloo procedure: symbol-plist symbol-or-keyword

Returns the property-list associated with symbol-or-keyword.

bigloo procedure: getprop symbol-or-keyword key

Returns the value that has the key eq? to key from the symbol-or-keyword’s property list. If there is no value associated with key then #f is returned.

bigloo procedure: putprop! symbol-or-keyword key val

Stores val using key on symbol-or-keyword’s property list.

bigloo procedure: remprop! symbol-or-keyword key

Removes the value associated with key in the symbol-or-keyword’s property list. The result is unspecified.

Here is an example of properties handling:

(getprop 'a-sym 'a-key)       ⇒ #f
(putprop! 'a-sym 'a-key 24)  
(getprop 'a-sym 'a-key)       ⇒ 24
(putprop! 'a-sym 'a-key2 25)  
(getprop 'a-sym 'a-key)       ⇒ 24
(getprop 'a-sym 'a-key2)      ⇒ 25
(symbol-plist 'a-sym)         ⇒ (a-key2 25 a-key 24)
(remprop! 'a-sym 'a-key)
(symbol-plist 'a-sym)         ⇒ (a-key2 25)
(putprop! 'a-sym 'a-key2 16)  
(symbol-plist 'a-sym)         ⇒ (a-key2 16)

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