evaluate structures

The evaluate module uses an evaluation environment (“eenv”) to manage the data it requires to evaluate source code expressions.

Several parts of the data structure are created directly for and are shared with the VM’s execution environment (“xenv”).

struct %eenv
Field:

desc

Field:

file

Field:

aot?

Field:

chksum

Field:

symbols

Field:

operators

Field:

predefs

Field:

ph

Field:

st

Field:

cs

Field:

ch

Field:

vt

Field:

module

Field:

escapes

Field:

ses

Field:

sps

Field:

byte-code

Field:

pcs

Field:

xi

Canonical:

evaluate/%eenv

  • desc is a description of the eenv

  • file is the file name of the source file associated with this eenv (which could be stdin)

    Note this is the source file not any (pre-compiled) cache file.

  • aotp is a flag indicating that the source code is being pre-compiled

  • chksum is a SHA256 digest of the source file (this is unlikely to be correct for stdin)

  • symbols is an associate list of symbol names and some symbol data tuples

    This is the primary evaluation data structure.

  • operators is a similar association list but for operators which need to be managed separately as they don’t exist in this module – all operators exist in the operator module as they are common to the reader.

  • predefs is a simple tuple of the predefs (primitives) used in this module

    When reading in a cached byte code file nothing will pre-set the predefs into the xenv symbol and value tables. Most of the time this doesn’t matter as a reference to the name will find the predef but there are corner cases, for example, where a closure shadows a predef, that pre-setting the predef is a requirement.

  • ph is a hash of the predefs being added (creating a set rather than duplicates)

  • st is the symbol table for the xenv, it is an array mapping a symbol table index, si, to constants table index, ci

    st and vt will align one-for one in an xenv

  • cs is the constants table for the xenv, an array mapping a constants table index, ci, to a constant value

    Any (constant) expression that isn’t a small positive integer will be in here.

  • ch is a hash of the constants table for the VM enabling faster lookups

  • vt is the values table for the xenv, an array mapping the xenv’s value table index, vi, to a global values table index (the table the VM actually cares about)

    st and vt will align one-for one in an xenv

  • module is a module being modified in this eenv

  • escapes isn’t used

  • ses is an array of source code expressions

    These are maintained during evaluation but are not saved as it is impossible to (sensibly) regenerate without re-parsing the source code.

  • sps is an array of source code properties

    In particular it is a set of (fi line) tuples where fi is an index into the constants table to the source code’s file name. line is the source code line number.

  • byte-code is the VM’s byte code

    This is saved as a byte string.

  • pcs is the list of initial program counters for the byte-code

    These reflect the top-level expressions in the source code.

  • xi is the xenv’s xenv index

Last built at 2025-02-05T07:10:34Z+0000 from 62cca4c (dev) for Idio 0.3.b.6