tlcore with demands

When the –demands option is set in tlcore, then it can handle demands. In this case, in each instant, there are four parts, not three. The fourth part is introduced with another %% pair, as follows:

header
%%
equations
%%
demands
%%
expressions
$$
header
%%
equations
%%
demands
%%
expressions
$$
...

A demand requests that a variable be computed in a specific context. It is written as a pair

(x,tuple);;

and it is registered internally by the system with a UUID. At each instant, should the tuple be valid in that instant, then this pair is evaluated, producing the result, along with the other expressions. The response for an instant therefore looks like this:

dem1 → demanswer1;;
...
demm → demanswerm ;;
%%
answer1;;
...
answern;;

If the –uuid option is set, then the UUID of the demands is printed out, as it is for equations:

eqnuuid1;;
...
eqnuuidl;;
%%
dem1 → demuuid1 → demanswer1;;
...
demm → demuuidm → demanswerm ;;
%%
answer1;;
...
answern;;

Should the –verbose option also be set, then the results will be of the form

eqn1 → eqnuuid1;;
...
eqnl → eqnuuidl;;
%%
dem1 → demuuid1 → demanswer1;;
...
demm → demuuidm → demanswerm ;;
%%
expr1 → answer1;;
...
exprn → answern;;

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