2.8 Miscellaneous features

2.8.1 Data types

Many loop constructs take a type-spec argument that allows you to specify certain data types for loop variables. While it is not necessary to specify a data type for any variable, by doing so you ensure that the variable has a correctly typed initial value. The type declaration is made available to the Compiler for more efficientloop expansion.

In Liquid Common Lisp, fixnum and float declarations are especially useful; the Compiler notices them and emits more efficient code. See the discussion of the loop methodelements in Section 2.9 on page 43 for more information about the Compiler's use of type specifiers.

Syntax ambiguities prevent the Loop Facility from supporting all Common Lisp type specifiers. The following type specifiers are supported by the Loop Facility:

t, specifying a Common Lisp data type that is a supertype of all other types and a proper subtype of none; it contains all objects.
number, specifying the Common Lisp data typenumber.
float, specifying a subtype of thenumber data type. The loopfloat data type is not a Common Lisp data type; it is the default floating-point representation in the implementation of Common Lisp that you are using.
integer, specifying a Common Lisp data type that consists of fixnums and bignums. Bignums and fixnums differ only in the magnitude of representation they allow; this distinction is generally not visible to the user.
fixnum, specifying a Common Lisp data type that is a subtype of theinteger data type. It allows integers in an implementation-defined range to be represented efficiently by a fixed number of bits.
notype, specifying a data type that is equivalent to the Common Lisp typet; it is not a Common Lisp data type but is supported for backward compatibility.

The Loop Facility - 9 SEP 1996

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