breeze

A dsl for writing macros in Nim

rationale

I read a comment by Araq about how karax might be a good fit for the ast nodes in the compiler and I've always found building the nodes in macro-s in Nim tedious. breeze is a karax-like dsl for building nim nodes in macros:

macro s(b: untyped): untyped =
  var e = newIdentNode(!"e")
  result = buildMacro:
    call:
      dotExpr(e, ident("f"))
      infix(ident("+"), 2, 3)

expands to

nnkCall.newTree(nnkDotExpr.newTree(e, newIdentNode(! "f")),
                nnkInfix.newTree(newIdentNode(! "+"), newLit(2), newLit(3)))

It's equivalent to

macro s(b: untyped): untyped =
  var e = newIdentNode(!"e")
  result = buildMacro:
    call:
      dotExpr:
        e
        ident("f")
      infix:
        ident("+")
        2
        3

functionality

You use it invoking buildMacro with a singular child corresponding to the node you want to build

Each child is either of the form

node:
  child
  child

or

node(child, child)

They're equivalent in most cases and they usually expand to nnk<capitalized_node>.newTree(<visited children>)

Special cases are literals which are expanded to newLit and ident(name) which are expanded to newIdentNode.

You can build dynamically macros (with variables) just by passing them directly, e.g.

var e = newIdentNode(!"f")
result = buildMacro:
  call:
    e

expands to

Call
  Ident !"f"