with-standard-io-syntax

with-standard-io-syntax Macro

Syntax:

with-standard-io-syntax {form}* → {result}*

Arguments and Values:

forms—an implicit progn.

results—the values returned by the forms.

Description:

Within the dynamic extent of the body of forms, all reader/printer control variables, including any implementation-defined ones not specified by this standard, are bound to values that produce standard read/print behavior. The values for the variables specified by this standard are listed in Figure 23–1.

|Variable Value|

| :- |

|

*package* The CL-USER package

*print-array* t

*print-base* 10

*print-case* :upcase

*print-circle* nil

*print-escape* t

*print-gensym* t

*print-length* nil

*print-level* nil

*print-lines* nil

*print-miser-width* nil

*print-pprint-dispatch* The standard pprint dispatch table *print-pretty* nil

*print-radix* nil

*print-readably* t

*print-right-margin* nil

*read-base* 10

*read-default-float-format* single-float

*read-eval* t

*read-suppress* nil

*readtable* The standard readtable

|

Figure 23–1. Values of standard control variables

Examples:

 
(with-open-file (file pathname :direction :output) 
(with-standard-io-syntax 
(print data file))) 
;;; ... Later, in another Lisp: 
(with-open-file (file pathname :direction :input) 
(with-standard-io-syntax 
(setq data (read file)))) 
 
 
*∗***read-base***∗ Variable* 

Value Type:

a radix .

Initial Value:

10.

Description:

Controls the interpretation of tokens by read as being integers or ratios.

The value of *read-base*, called the current input base, is the radix in which integers and ratios are to be read by the Lisp reader . The parsing of other numeric types (e.g., floats) is not affected by this option.

The effect of *read-base* on the reading of any particular rational number can be locally overridden by explicit use of the #O, #X, #B, or #nR syntax or by a trailing decimal point.

Examples:

(dotimes (i 6) 
  (let ((\*read-base\* (+ 10. i))) 
    (let ((object (read-from-string "(\\DAD DAD |BEE| BEE 123. 123)"))) 
      (print (list \*read-base\* object))))) 
▷ (10 (DAD DAD BEE BEE 123 123)) 
▷ (11 (DAD DAD BEE BEE 123 146)) 
▷ (12 (DAD DAD BEE BEE 123 171)) 
▷ (13 (DAD DAD BEE BEE 123 198)) 
▷ (14 (DAD 2701 BEE BEE 123 227)) 
▷ (15 (DAD 3088 BEE 2699 123 258)) 
→ NIL 

Notes:

Altering the input radix can be useful when reading data files in special formats.

Expanded Reference: with-standard-io-syntax

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