using and import names

Writing containers. in front of every name is clear, but it gets long in a file that uses one module heavily. Two tools shorten it: #import … as gives the module another name in this file, and using makes a module's public names usable with no prefix at all.

'' "as" gives a module a different name in this file.
#import "std/strings" as txt
#import "std/containers"

'' using makes a module's public names usable without the prefix.
using containers

dim primes as Array( of int32 )
for n as int32 = 2 to 20
    var isPrime = true
    for d as int32 = 2 to n - 1
        if n mod d = 0 then isPrime = false : exit for
    next
    if isPrime then primes.Push( n )
next

print txt.Format( "{} primes below 20", primes.Count( ) )
print txt.Format( "the largest is {}", primes[primes.Count( ) - 1] )

'' The qualified name still works under using.
dim names as containers.Array( of ustring )
names.Push( "tiko" )
print txt.PadLeft( names[0], 8, "." )

Output

8 primes below 20
the largest is 19
....tiko

• #import "std/strings" as txt renames the module for this file only. The module is still strings; only the spelling here changes. Use it when two imports end in the same name, or when a name is long. The new name must not be a keyword or a built-in: as str is refused, because str is a built-in function.
• using containers makes Array a bare name from that line to the end of the file. Written inside a procedure, it lasts to the end of the procedure. The qualified spelling, containers.Array, keeps working.

using makes names available; it never chooses between two of them. When two modules you are using both supply a name, a bare use of it is refused:

'' Two modules under using both supply Contains.
#import "std/strings"
#import "std/containers"
using strings
using containers

print Contains( "tiko", "k" )      '' refused: which Contains?

ambiguous.tiko(7,7): error TKO0919: 'contains' is ambiguous: more than one USING in effect declares it; qualify it
     |
   7 | print Contains( "tiko", "k" )      '' refused: which Contains?
     |       ^

Write strings.Contains and the question has an answer in the source.

Activities

1. Remove using containers and fix the program by qualifying Array.
2. Move using containers inside a sub and find the first line where Array is no longer a bare name.