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import macros
macro class*(head, body: untyped): untyped =
# The macro is immediate, since all its parameters are untyped.
# This means, it doesn't resolve identifiers passed to it.
var typeName, baseName: NimNode
# flag if object should be exported
var exported: bool
if head.kind == nnkInfix and head[0].kind == nnkIdent and $head[0] == "of":
# `head` is expression `typeName of baseClass`
# echo head.treeRepr
# --------------------
# Infix
# Ident !"of"
# Ident !"Animal"
# Ident !"RootObj"
typeName = head[1]
baseName = head[2]
elif head.kind == nnkInfix and head[0].kind == nnkIdent and
$head[0] == "*" and head[2].kind == nnkPrefix and
head[2][0].kind == nnkIdent and $head[2][0] == "of":
# `head` is expression `typeName* of baseClass`
# echo head.treeRepr
# --------------------
# Infix
# Ident !"*"
# Ident !"Animal"
# Prefix
# Ident !"of"
# Ident !"RootObj"
typeName = head[1]
baseName = head[2][1]
exported = true
else:
quit "Invalid node: " & head.lispRepr
# The following prints out the AST structure:
#
# import macros
# dumptree:
# type X = ref object of Y
# z: int
# --------------------
# StmtList
# TypeSection
# TypeDef
# Ident !"X"
# Empty
# RefTy
# ObjectTy
# Empty
# OfInherit
# Ident !"Y"
# RecList
# IdentDefs
# Ident !"z"
# Ident !"int"
# Empty
# create a type section in the result
result = newNimNode(nnkStmtList)
result.add(
if exported:
# mark `typeName` with an asterisk
quote do:
type `typeName`* = ref object of `baseName`
else:
quote do:
type `typeName` = ref object of `baseName`
)
# echo treeRepr(body)
# --------------------
# StmtList
# VarSection
# IdentDefs
# Ident !"name"
# Ident !"string"
# Empty
# IdentDefs
# Ident !"age"
# Ident !"int"
# Empty
# MethodDef
# Ident !"vocalize"
# Empty
# Empty
# FormalParams
# Ident !"string"
# Empty
# Empty
# StmtList
# StrLit ...
# MethodDef
# Ident !"age_human_yrs"
# Empty
# Empty
# FormalParams
# Ident !"int"
# Empty
# Empty
# StmtList
# DotExpr
# Ident !"this"
# Ident !"age"
# var declarations will be turned into object fields
var recList = newNimNode(nnkRecList)
# expected name of constructor
let ctorName = newIdentNode("new" & $typeName)
# Iterate over the statements, adding `this: T`
# to the parameters of functions, unless the
# function is a constructor
for node in body.children:
case node.kind:
of nnkMethodDef, nnkProcDef:
# check if it is the ctor proc
if node.name.kind != nnkAccQuoted and node.name.basename == ctorName:
# specify the return type of the ctor proc
node.params[0] = typeName
else:
# inject `self: T` into the arguments
node.params.insert(1, newIdentDefs(ident("self"), typeName))
result.add(node)
of nnkVarSection:
# variables get turned into fields of the type.
for n in node.children:
recList.add(n)
else:
result.add(node)
# Inspect the tree structure:
#
# echo result.treeRepr
# --------------------
# StmtList
# TypeSection
# TypeDef
# Ident !"Animal"
# Empty
# RefTy
# ObjectTy
# Empty
# OfInherit
# Ident !"RootObj"
# Empty <= We want to replace this
# MethodDef
# ...
result[0][0][2][0][2] = recList
# Lets inspect the human-readable version of the output
#echo repr(result)
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