std/macrocache

This module provides an API for macros to collect compile-time information across module boundaries. It should be used instead of global {.compileTime.} variables as those break incremental compilation.

The main feature of this module is that if you create CacheTables or any other Cache types with the same name in different modules, their content will be shared, meaning that you can fill a CacheTable in one module, and iterate over its contents in another.

Example:

import std/macrocache
import std/macros

const mcTable = CacheTable"myTable"
const mcSeq = CacheSeq"mySeq"
const mcCounter = CacheCounter"myCounter"

static:
  # add new key "val" with the value `myval`
  let myval = newLit("hello ic")
  mcTable["val"] = myval
  assert mcTable["val"].kind == nnkStrLit

# Can access the same cache from different static contexts
# All the information is retained
static:
  # get value from `mcTable` and add it to `mcSeq`
  mcSeq.add(mcTable["val"])
  assert mcSeq.len == 1

static:
  assert mcSeq[0].strVal == "hello ic"

  # increase `mcCounter` by 3
  mcCounter.inc(3)
  assert mcCounter.value == 3

Types

CacheCounter = distinct string

Compile-time counter, uses int for storing the count. Source Edit

CacheSeq = distinct string

Compile-time sequence of NimNodes. Source Edit

CacheTable = distinct string

Compile-time table of key-value pairs.

Keys are strings and values are NimNodes.

Source Edit

Procs

proc `[]`(s: CacheSeq; i: BackwardsIndex): NimNode {....raises: [], tags: [],
    forbids: [].}

Returns the ith last value from s.

Example:

import std/macros

const mySeq = CacheSeq"backTest"
static:
  mySeq &= newLit(42)
  mySeq &= newLit(7)
  assert mySeq[^1].intVal == 7  # Last item
  assert mySeq[^2].intVal == 42 # Second last item

Source Edit

proc `[]`(s: CacheSeq; i: int): NimNode {.magic: "NcsAt", ...raises: [], tags: [],
    forbids: [].}

Returns the ith value from s.

Example:

import std/macros

const mySeq = CacheSeq"subTest"
static:
  mySeq.add(newLit(42))
  assert mySeq[0].intVal == 42

Source Edit

proc `[]`(t: CacheTable; key: string): NimNode {.magic: "NctGet", ...raises: [],
    tags: [], forbids: [].}

Retrieves the NimNode value at t[key].

Example:

import std/macros

const mcTable = CacheTable"subTest"
static:
  mcTable["toAdd"] = newStmtList()

  # get the NimNode back
  assert mcTable["toAdd"].kind == nnkStmtList

Source Edit

proc `[]=`(t: CacheTable; key: string; value: NimNode) {.magic: "NctPut",
    ...raises: [], tags: [], forbids: [].}

Inserts a (key, value) pair into t.

Warning: key has to be unique! Assigning value to a key that is already in the table will result in a compiler error.

Example:

import std/macros

const mcTable = CacheTable"subTest"
static:
  # assign newLit(5) to the key "value"
  mcTable["value"] = newLit(5)

  # check that we can get the value back
  assert mcTable["value"].kind == nnkIntLit

Source Edit

proc add(s: CacheSeq; value: NimNode) {.magic: "NcsAdd", ...raises: [], tags: [],
                                        forbids: [].}

Adds value to s.

Example:

import std/macros
const mySeq = CacheSeq"addTest"

static:
  mySeq.add(newLit(5))
  mySeq.add(newLit("hello ic"))

  assert mySeq.len == 2
  assert mySeq[1].strVal == "hello ic"

Source Edit

proc contains(t: CacheTable; key: string): bool {.inline, ...raises: [], tags: [],
    forbids: [].}

Alias of hasKey for use with the in operator.

Example:

import std/macros
const mcTable = CacheTable"containsEx"
static:
  mcTable["foo"] = newEmptyNode()
  # Will be true since we gave it a value before
  assert "foo" in mcTable

Source Edit

proc hasKey(t: CacheTable; key: string): bool {....raises: [], tags: [],
    forbids: [].}

Returns true if key is in the table t.

See also:

• contains proc for use with the in operator

Example:

import std/macros
const mcTable = CacheTable"hasKeyEx"
static:
  assert not mcTable.hasKey("foo")
  mcTable["foo"] = newEmptyNode()
  # Will now be true since we inserted a value
  assert mcTable.hasKey("foo")

Source Edit

proc inc(c: CacheCounter; by = 1) {.magic: "NccInc", ...raises: [], tags: [],
                                    forbids: [].}

Increments the counter c with the value by.

Example:

static:
  let counter = CacheCounter"incTest"
  inc counter
  inc counter, 5

  assert counter.value == 6

Source Edit

proc incl(s: CacheSeq; value: NimNode) {.magic: "NcsIncl", ...raises: [], tags: [],
    forbids: [].}

Adds value to s.

Hint: This doesn't do anything if value is already in s.

Example:

import std/macros
const mySeq = CacheSeq"inclTest"

static:
  mySeq.incl(newLit(5))
  mySeq.incl(newLit(5))

  # still one element
  assert mySeq.len == 1

Source Edit

proc len(s: CacheSeq): int {.magic: "NcsLen", ...raises: [], tags: [], forbids: [].}

Returns the length of s.

Example:

import std/macros

const mySeq = CacheSeq"lenTest"
static:
  let val = newLit("helper")
  mySeq.add(val)
  assert mySeq.len == 1

  mySeq.add(val)
  assert mySeq.len == 2

Source Edit

proc len(t: CacheTable): int {.magic: "NctLen", ...raises: [], tags: [],
                               forbids: [].}

Returns the number of elements in t.

Example:

import std/macros

const dataTable = CacheTable"lenTest"
static:
  dataTable["key"] = newLit(5)
  assert dataTable.len == 1

Source Edit

proc value(c: CacheCounter): int {.magic: "NccValue", ...raises: [], tags: [],
                                   forbids: [].}

Returns the value of a counter c.

Example:

static:
  let counter = CacheCounter"valTest"
  # default value is 0
  assert counter.value == 0

  inc counter
  assert counter.value == 1

Source Edit

Iterators

iterator items(s: CacheSeq): NimNode {....raises: [], tags: [], forbids: [].}

Iterates over each item in s.

Example:

import std/macros
const myseq = CacheSeq"itemsTest"

static:
  myseq.add(newLit(5))
  myseq.add(newLit(42))

  for val in myseq:
    # check that all values in `myseq` are int literals
    assert val.kind == nnkIntLit

Source Edit

iterator pairs(t: CacheTable): (string, NimNode) {....raises: [], tags: [],
    forbids: [].}

Iterates over all (key, value) pairs in t.

Example:

import std/macros
const mytabl = CacheTable"values"

static:
  mytabl["intVal"] = newLit(5)
  mytabl["otherVal"] = newLit(6)
  for key, val in mytabl:
    # make sure that we actually get the same keys
    assert key in ["intVal", "otherVal"]

    # all vals are int literals
    assert val.kind == nnkIntLit

Source Edit