Constructs

There are two looping constructs and a conditional construct. The basic looping construct has the form while ... do ... wend. While the expression to the left of the do keyword is true do the expression to the right of the do keyword. The expression on the left must produce a boolean value. The left and right expressions can include any complex expression, such as nested looping and conditional constructs or function calls. An example of this looping construct is given below with the definition of strlen (to return the length of a string).

%%EQUATE strlen(s)
  0 >> x
  while s'x <> 0 do
    x + 1 >> x
  wend
  outputs(x)

The other looping construct has the form roll ... through. The expression between the keywords is executed once for every record in the master database (filter conditions still apply). For example here is the definition of a function to return the number of records in the database.

%%EQUATE nrecs
  0 >> n
  roll n + 1 >> n through
  outputs(n)

The looping syntax can optionally include a colon suffix form. This allows looping through a named database (no filter conditions apply when this is the master database). This form is roll ... through:database where database is the name of a valid loaded database (without the pathname or extension). Fields from other databases cannot be accessed within the loop unless the -> syntax is used, so if looping through a database other than the master database then this form must be used within the loop to access fields of the master database. Note that this applies even to nested equate calls within the loop body for example.

The conditional construct has one of the forms if ... then ... endif and if ... then ... else ... endif. If the boolean expression bewteen the if and then keywords is true execute the expression between the then and else or endif keywords otherwise execute the expression between the else and the endif keywords if it exists. Each expression can be as complex as required (including nested conditional and looping constructs, and function calls) but need not have any contents. Below are two examples of the conditional construct.

%%EQUATE test
  inputs(a,c)
  if a > 0 and a < 12 then "hello" >> b endif
  if not (c = 5) then
    5 >> c
    "no" >> b
  else
    if not (c = 3) then 3 >> c "world" >> b
    endif
  endif
  outputs(b,c)

Note that the endif keyword must always be present. The elif keyword can be used for multiple conditions grouped up under one endif keyword (this saves having to nest conditions). The example above is shown below using the elif keyword to simplify the statements.

%%EQUATE test
  inputs(a,c)
  if a > 0 and a < 12 then "hello" >> b endif
  if not (c = 5) then 5 >> c "no" >> b
  elif not (c = 3) then 3 >> c "world" >> b
  endif
  outputs(b,c)

There is a known bug preventing the use of a roll .. through construct within a condition construct when the colon suffix form is used.

Go to the first, previous, next, last section, table of contents.