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Allocate Token Range {R}←{X} ⎕TALLOC Y

Y is either a single integer or a 2-element vector. The first (or only) item in Y is 0, 1, 2 or ¯1 and indicates the type of operation to perform. If it is 1, then the optional second item is a character vector.

The optional left argument X identifies an existing allocated range of token numbers n. X must be a scalar greater than or equal to n, but must be less than n+1.

Allocation (First element of Y is 1)

If the first element of Y is 1, the result R is a positive integer that identifies a range of numbers that may be used as token types for ⎕TPUT and ⎕TGET. That range is defined as the set of floating-point numbers between R and R+1 (but not the integer end-points). Negated values of these number may also be used.

In this case, the optional Y[2] is an arbitrary character vector that serves as a description for the allocated range of tokens.

De-allocation (Y is ¯1)

If Y is ¯1, ⎕TALLOC releases a previously allocated range of tokens identified by the left-argument X. The result R is a shy ⍬.

To succeed, this range must have previously been allocated, not freed by de-allocation, and must be inactive, that is, its tokens must not currently be in the token pool or in use by a ⎕TGET. If not, ⎕TALLOC will signal a DOMAIN ERROR.

A de-allocated range becomes free for subsequent re-allocation by ⎕TALLOC.

Querying a description (Y is 0)

Y is 0, ⎕TALLOC returns a non-shy result R containing the description for a currently allocated range of tokens identified by the left-argument X.

If X does not represent a currently allocated range, ⎕TALLOC will signal a DOMAIN ERROR.

If X is omitted, the result R is a vector of 2-element vectors identifying the range and description of all currently allocated ranges.

Descriptions that were not defined are returned as empty character vectors.

Querying the Token Pool (Y is 2)

Y is 2, ⎕TALLOC returns a non-shy result R containing the list of tokens in the token pool that fall in the range specified by the left-argument X.

Examples

       ⎕←trg←⎕TALLOC 1 'cats'
1
       ⎕TALLOC 0
┌────────┐
│┌─┬────┐│
││1│cats││
│└─┴────┘│
└────────┘
      ⎕TPUT trg+.1 .2 .3
      ⎕TPUT -trg+.9
      ⎕TPOOL             
1.1 1.2 1.3 ¯1.9

      ⎕TGET trg+.1 .2 .3 .9

      1 ⎕TALLOC ¯1 ⍝ Try to de-allocate the range     
DOMAIN ERROR
      1 ⎕TALLOC ¯1 
        ∧
      1 ⎕TALLOC 2  ⍝ Failed due to ¯1.9 token
¯1.9
      ⎕TGET ¯1.9   ⍝ Remove the inexhaustible ¯1.9 token
      1 ⎕TALLOC 2

      1 ⎕TALLOC ¯1 ⍝ De-allocation now works