gensym

(gensym [prefix])

Returns a fresh symbol named #:<prefix><n>, where prefix defaults to G and n is a program-wide counter starting at 1. rontolisp has no uninterned symbols: the result is an ordinary symbol whose uniqueness rests on the #: prefix (which no user-written name normally carries) and the ever-increasing counter. Its main use is generating capture-safe temporaries inside defmacro bodies, replacing the older __-prefixed naming convention.

Deviations from Common Lisp: the prefix must be a literal string on the compilation path (JVM/WASM), so the symbol text is known at compile time — a computed prefix is a compile error (the interpreter accepts any string). There is no *gensym-counter* variable, and because the symbol is interned like any other, reading the same printed name twice yields eq symbols.

The optional argument may also be a non-negative integer: it is used as the suffix directly, under the default G prefix, and does not advance the counter — the next plain (gensym) still gets the number it would have gotten anyway.

A macro temporary generated with gensym cannot collide with the caller's variables: