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|
import macros
# backported list comprehension from earlier nim versions
type ListComprehension = object
var lc*: ListComprehension
template `|`*(lc: ListComprehension, comp: untyped): untyped = lc
macro `[]`*(lc: ListComprehension, comp, typ: untyped): untyped =
expectLen(comp, 3)
expectKind(comp, nnkInfix)
assert($comp[0] == "|")
result = newCall(newDotExpr(newIdentNode("result"), newIdentNode("add")), comp[1])
for i in countdown(comp[2].len - 1, 0):
let x = comp[2][i]
expectMinLen(x, 1)
if x[0].kind == nnkIdent and x[0].strVal == "<-":
expectLen(x, 3)
result = newNimNode(nnkForStmt).add(x[1], x[2], result)
else:
result = newIfStmt((x, result))
result = newNimNode(nnkCall).add(newNimNode(nnkPar)
.add(newNimNode(nnkLambda).add(newEmptyNode(), newEmptyNode(), newEmptyNode(),
newNimNode(nnkFormalParams).add(newNimNode(nnkBracketExpr).add(newIdentNode("seq"), typ)),
newEmptyNode(), newEmptyNode(), newStmtList(newAssignment(newIdentNode("result"),
newNimNode(nnkPrefix).add(newIdentNode("@"), newNimNode(nnkBracket))), result))))
|
