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| -rw-r--r-- | txr.1 | 38 |
1 files changed, 38 insertions, 0 deletions
@@ -3621,6 +3621,43 @@ Dialect Note: unlike in Common Lisp, is not an integer, but the floating-point number .codn 123.0 . +Integers within a certain small range centered on zero have +.code fixnum +type. Values in the +.code fixnum +range fit into a Lisp value directly, not requiring heap allocation. +A value which is implemented as a reference to a heap-allocated +object is called +.IR boxed , +whereas a self-contained value not referencing any storage +elsewhere is called +.IR unboxed . +Thus values in the +.code fixnum +are unboxed; those outside of the range have +.code bignum +type instead, and are boxed. The variables +.code fixnum-min +and +.code fixnum-max +indicate the range. + +Floating-point values are all unboxed if \*(TX is built with "NaN boxing" +enabled, otherwise they are all boxed. The Lisp expression +.code "(eq (read \(dq0.0\(dq) (read \(dq0.0\(dq))" +returns +.code t +under NaN boxing, indicating that the two instances of 0.0 are the +same object. In the absence of NaN boxing, the two +.code read +calls produce distinct, boxed representations of 0.0, which +compare unequal under +.codn eq . +(The expression +.code "(eq 0.0 0.0)" +may not be relied upon if it is compiled, since compilation may deduplicate +identical boxed literals, leading to a false positive.) + .SS* Comments Comments of the form @@ -14460,6 +14497,7 @@ Lisp variables using the prefix, which is a consequence of that prefix introducing an expression that is evaluated as Lisp, the name of a variable being such an expression. + .SH* LISP OPERATOR, FUNCTION AND MACRO REFERENCE .SS* Conventions |