Data Types 2

Array = homogenous collection
q: what types for subscripts, do we rangecheck, are ranges bound, array alloc when, how many subscripts (1,2), initialization, are slices allowed?
FORTRAN:
SUM = SUM + B(I)
same () as functions so needs keep track. why? no other chars avail. Ada as well - because both are mappings of parameters to values. Pascal, C++, Java = []

obvious point: element type vs. subscript type. most often subrange of int. Pascal, Ada: Bool, char, enum.

subrange checking: Pascal, Ada, Java. Not C++, FORTRAN - out of bound errors. speed vs. reliability.

Binding of subscript type statically bound (usually) but value range can s/t vary dynamically.

lower bound: 0, 1, set by user.

4 cat, based on binding to subscript range and binding to storage.
static array - both ranges and binding to storage at compile time. no dynamic alloc dealloc. FORTRAN 77.
fixed stack-dynamic - subscripts bound statically, storage bound off the stack - C, Pascal.
stack-dynamic - same as above but subscript bound dynamically as well. but then remain fixed for lifetime of var. Ada:
GET (LIST_LEN)
declare
LIST : array (1..LIST_LEN) of INTEGER
begin
...
end
heap-dynamic - same, but can change many times during lifetime. FORTRAN 90:
INTEGER, ALLOCATABLE, ARRAY (:, :) :: MAT
ALLOCATE (MAT(10, NUMBER_OF_COLUMNS)
DEALLOCATE(MAT)
same idea in C, C++ using pointers.

Number of Subscripts
saw in fortran assignment that could use mult indices. original fortran restricted to 3. The ZERO-ONE-INFINITE principle. Let programmer bear the cost if he wants. FORTRAN IV it became 7. Modern - unlimited.

Array init: FORTRAN has it in the form of a DATA statement:
DATA MYVAR / 8, 9, 10/
in C, init of arrays, of strings, of arrays of strings. In Java.
Ada:
LIST : array (1..5) of INTEGER := (1, 4, 6, 8, 10)
LIST : array (1..5) of INTEGER := (1 => 3, 4 => 9, others =>0)

array ops


to be continued...