7.4 STASH and RETRIEVE

The NEXT stack is not the only stack available in an INTERCAL program; each variable used in the program also has its own stack, which holds values of the same type as the variable. The STASH command pushes a variable’s value onto that variable’s stack; RETRIEVE can be used in the same way to pop the top element of a variable’s stack to replace that variable’s value. The syntax is the same as most other INTERCAL commands, with the word STASH or RETRIEVE followed by the variable or variables to stash or retrieve:

DO STASH .1 + ;2
DO RETRIEVE ,3

Note that it is possible to stash or retrieve multiple variables at once, by listing their names separated by intersections (+); it’s even possible to stash or retrieve a variable twice in the same statement.

It is not entirely clear how RETRIEVE interacts with IGNORE in historical INTERCAL-72 compilers; the three modern INTERCAL compilers all use different rules for the interaction (and the C-INTERCAL maintainers recommend that if anyone decides to write their own compiler, they choose yet another different rule so that looking at the interaction (the so-called ‘ignorret test’) can be used as a method of determining which compiler is running):

• C-INTERCAL treats a retrieval just like an assignment. That is, a read-only variable will not be changed by a retrieval, and will remain read-only, but the side-effect of popping that variable’s stash will still happen.
• J-INTERCAL ignores the read-only status of a variable when retrieving it from a stash; the value of the variable changes despite being read-only. The variable remains read-only; the RETRIEVE simply allows a change to its value despite the read-only status.
• CLC-INTERCAL is the most complicated; it stores read-only status or otherwise in the stash, along with the variable’s value. This means that if a variable was stashed when read-only, retrieving it will retrieve its value and set it to read-only regardless of its previous read-only status; likewise, if a variable was stashed when read-write, retrieving it will retrieve its value and set it to read-write even if it was previously read-only.

The appropriate gerunds for STASH and RETRIEVE are STASHING and RETRIEVING respectively.