Calling Other Equates

Any equate can be called from within an equate. It can be passed arguments and any value returned can be assigned to a variable or used in an expression. An equate is called by simply giving its name (with optional brackets). If the equate matches the name of a local variable then the value of the variable will be returned else the equate will be called to return a value. An equate need not take any arguments nor return any value although they commonly do. Arguments are passed to an equate as a comma separated list of expressions between brackets that immediately follow the equate name. If the equate returns one argument this can be simply assigned to a variable, or used in an expression. If the equate returns multiple arguments then the @(...) operator sequence should be used to assign the results to multiple variables. Some examples of equate calls are shown below.

%%EQUATE test
  "hello" >> s
  "b" + substr(s,1,1+3) + "ws" >> s

Using the previously defined equate substr() the above would result in "bellows" being assigned to s.

Arguments to an equate are defined using the inputs(...) keyword sequence. Between the brackets there can be nothing or there should be a comma separated list of variable names to which the arguments passed into the equate will be assigned (the variables will be created with the data type of the argument passed in). Instead of using the inputs keyword it is also possible to put the bracket sequence immediately following the definition of the equate name. The return values from an equate are similarly defined using the outputs(...) keyword sequence. This takes a comma separated list of expressions (normally just one) the values of which are returned to the calling equate. Both the inputs and outputs keyword sequences are optional but if they are used the inputs must be the first line of the equate and the outputs must be the last line of the equate (or at least the last executed expression) - the outputs keyword cannot be used as a return escape. The example below shows the definition of an equate that takes two arguments and swaps the values around while also adding 10 to each value returning the two swapped arguments and then an example of that equate being called.

%%EQUATE swap
  inputs(a,b)
  outputs(b+10,a+10)
%%EQUATE test
  5 >> x
  7 >> y
  swap(x,y)@(x,y)

The test equate will result in x equaling 17 and y equaling 15. Note the use of the @ operator to handle the passing back of multiple arguments. Note that swap(x,y) >> y >> x would be equivalent to the above but the assignments must be put in reverse order to the arguments sent back.

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