Ada Programming/Keywords/for


Ada Lovelace 1838.jpg


This keyword is used in:

  • For loops
  • Representation clauses:
    • attribute definition clause
    • enumeration representation clause
    • record representation clause
    • at clause (obsolescent)
  • Quantified expressions
    • Universal quantification
    • Existential quantification

Nowadays representation clauses are formally called aspect clauses in the last versions of the Reference Manual due to some technicalities, although representation clauses is the name far more extended among Ada programmers. As a historical note, they were known as representation specifications (rep specs) in pre-Ada 83 proposals.[1]

For loopsEdit

[loop name :] for var in [ reverse ] [type range] range loop
   ...
end loop;

Where range can be:

  • explicit range like "low .. high",
  • range of scalar or array type: type'Range (or type'Range(n) for multidimensional array types)
  • range of an array: array'Range (or array'Range(n) for multidimensional arrays)

Representation clausesEdit

Attribute definition clauseEdit

for id'attribute use value;

Where attribute can be any specifiable attribute.

Enumeration representation clauseEdit

for enumeration type use (enum1 => value1, enum2 => value2, ...);

Record representation clauseEdit

for record type use
  record
     component1 at offset range first bit 1 .. last bit 1;
     component2 at offset range first bit 2 .. last bit 2;
     ...
  end record;

At clause (obsolescent)Edit

At clauses are obsolescent since Ada 95:

for id use at address;

where address is of the type System.Address.

An at clause is equivalent to "for id'Address use address;". Since Ada 95 this is the preferred method.

Quantified expressionsEdit

This language feature is only available in Ada 2012.

Universal quantificationEdit

Universal quantification expression:

(for all var in range => predicate)

Existential quantificationEdit

Existential quantification expression:

(for some var in range => predicate)

See alsoEdit

WikibookEdit

Ada Reference ManualEdit

Ada 83Edit

Ada Quality and Style GuideEdit

ReferencesEdit

  1. John Barnes (2003-03-25). High-Integrity Software — The SPARK Approach to Safety and Security. Addison-Wesley. ISBN 0-321-13616-0. http://www.praxis-his.com/sparkada/sparkbook.asp. Retrieved 2008-06-06. "Representation clauses are now strictly known as aspect clauses — the name was changed in the 2000 Corrigendum for Ada 95 for subtle reasons that need not concern us; Ada historians might recall that they were known as representation specifications (rep specs) prior to the ANSI standardization in 1983. These various terminologies are all in use and the reader will encounter them in the literature. (pp.212–213)" 



Ada Keywords
abort else new return
abs elsif not reverse
abstract (Ada 95) end null
accept entry select
access exception of separate
aliased (Ada 95) exit or some (Ada 2012)
all others subtype
and for out synchronized (Ada 2005)
array function overriding (Ada 2005)
at tagged (Ada 95)
generic package task
begin goto pragma terminate
body private then
if procedure type
case in protected (Ada 95)
constant interface (Ada 2005) until (Ada 95)
is raise use
declare range
delay limited record when
delta loop rem while
digits renames with
do mod requeue (Ada 95) xor
Last modified on 27 February 2012, at 21:17