Macros
macro genAstOpt(options: static set[GenAstOpt]; args: varargs[untyped]): untyped
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Accepts a list of captured variables a=b or a and a block and returns the AST that represents it. Local {.inject.} symbols (e.g. procs) are captured unless kDirtyTemplate in options.
Example:
# This example shows how one could write a simplified version of `unittest.check`. import std/[macros, strutils] macro check2(cond: bool): untyped = assert cond.kind == nnkInfix, "$# not implemented" % $cond.kind result = genAst(cond, s = repr(cond), lhs = cond[1], rhs = cond[2]): # each local symbol we access must be explicitly captured if not cond: doAssert false, "'$#'' failed: lhs: '$#', rhs: '$#'" % [s, $lhs, $rhs] let a = 3 check2 a*2 == a+3 if false: check2 a*2 < a+1 # would error with: 'a * 2 < a + 1'' failed: lhs: '6', rhs: '4'
Example:
# This example goes in more details about the capture semantics. macro fun(a: string, b: static bool): untyped = let c = 'z' var d = 11 # implicitly {.gensym.} and needs to be captured for use in `genAst`. proc localFun(): auto = 12 # implicitly {.inject.}, doesn't need to be captured. genAst(a, b, c = true): # `a`, `b` are captured explicitly, `c` is a local definition masking `c = 'z'`. const b2 = b # macro static param `b` is forwarded here as a static param. # `echo d` would give: `var not init` because `d` is not captured. (a & a, b, c, localFun()) # localFun can be called without capture. assert fun("ab", false) == ("abab", false, true, 12)
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