27. "Data Types"

.setq loop-data-type-section css-number .setq loop-data-type-page page .topic data type keywords In many of the clause descriptions, an optional data-type is shown. A data-type in this sense is an atomic symbol, and is recognizable as such by loop. These are used for declaration and initialization purposes; for example, in

(loop for x in l
      maximize x flonum into the-max
      sum x flonum into the-sum
      ...)

the flonum data-type keyword for the maximize clause says that the result of the max operation, and its "argument" (x), will both be flonums; hence loop may choose to code this operation specially since it knows there can be no contagious arithmetic. The flonum data-type keyword for the sum clause behaves similarly, and in addition causes the-sum to be correctly initialized to 0.0 rather than 0. The flonum keywords will also cause the variables the-max and the-sum to be declared to be flonum, in implementations where such a declaration exists. In general, a numeric data-type more specific than number, whether explicitly specified or defaulted, is considered by loop to be license to generate code using type-specific arithmetic functions where reasonable. The following data-type keywords are recognized by loop (others may be defined; for that, consult the source code):

fixnum: An implementation-dependent limited range integer.
flonum: An implementation-dependent limited precision floating point number.
small-flonum: This is recognized in the Zetalisp implementation only, where its only significance is for initialization purposes, since no such declaration exists.
integer: Any integer (no range restriction).
number: Any number.
notype: Unspecified type (i.e., anything else).

Note that explicit specification of a non-numeric type for an operation which is numeric (such as the summing clause) may cause a variable to be initialized to nil when it should be 0. If local data-type declarations must be inhibited, one can use the nodeclare clause, which is described on (loop-nodeclare-clause).

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This document was generated by Brad Parker on June, 13 2006 using texi2html