Base and optional features (Revised7.0 Report on the Algorithmic Language Scheme (Unofficial))

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1.3.1 Base and optional features ¶

Every identifier defined in this report appears in one or more of several libraries. Identifiers defined in the base library are not marked specially in the body of the report. This library includes the core syntax of Scheme and generally useful procedures that manipulate data. For example, the variable abs is bound to a procedure of one argument that computes the absolute value of a number, and the variable + is bound to a procedure that computes sums. The full list of all the standard libraries and the identifiers they export is given in Appendix A (Standard Libraries).

All implementations of Scheme:

Must provide the base library and all the identifiers exported from it.
May provide or omit the other libraries given in this report, but each library must either be provided in its entirety, exporting no additional identifiers, or else omitted altogether.
May provide other libraries not described in this report.
May also extend the function of any identifier in this report, provided the extensions are not in conflict with the language reported here.
Must support portable code by providing a mode of operation in which the lexical syntax does not conflict with the lexical syntax described in this report.