discard """
file: "tstringinterp.nim"
output: "Hello Alice, 64 | Hello Bob, 10$"
"""
import macros, parseutils, strutils
proc concat(strings: varargs[string]): string =
result = newString(0)
for s in items(strings): result.add(s)
template processInterpolations(e) =
var s = e[1].strVal
for f in interpolatedFragments(s):
case f.kind
of ikStr: addString(f.value)
of ikDollar: addDollar()
of ikVar, ikExpr: addExpr(newCall("$", parseExpr(f.value)))
macro formatStyleInterpolation(e: untyped): untyped =
let e = callsite()
var
formatString = ""
arrayNode = newNimNode(nnkBracket)
idx = 1
proc addString(s: string) =
formatString.add(s)
proc addExpr(e: NimNode) =
arrayNode.add(e)
formatString.add("$" & $(idx))
inc idx
proc addDollar() =
formatString.add("$$")
processInterpolations(e)
result = parseExpr("\"x\" % [y]")
result[1].strVal = formatString
result[2] = arrayNode
macro concatStyleInterpolation(e: untyped): untyped =
let e = callsite()
var args: seq[NimNode]
newSeq(args, 0)
proc addString(s: string) = args.add(newStrLitNode(s))
proc addExpr(e: NimNode) = args.add(e)
proc addDollar() = args.add(newStrLitNode"$")
processInterpolations(e)
result = newCall("concat", args)
###
proc sum(a, b, c: int): int =
return (a + b + c)
var
alice = "Alice"
bob = "Bob"
a = 10
b = 20
c = 34
var
s1 = concatStyleInterpolation"Hello ${alice}, ${sum(a, b, c)}"
s2 = formatStyleInterpolation"Hello ${bob}, ${sum(alice.len, bob.len, 2)}$$"
write(stdout, s1 & " | " & s2)