Comparing expressions is useful if you want to write a test case for a function that transforms expressions, such as e.g. `@fastmath`. I recently added some test cases, but was unable to test the result of
macroexpand(:@fastmath :+) since I don't know how to explicitly construct the expected result. I know how to do it in the REPL, but this doesn't work in test cases. -erik On Wed, Dec 9, 2015 at 3:46 PM, Yichao Yu <yyc1...@gmail.com> wrote: > On Wed, Dec 9, 2015 at 3:05 PM, <vish...@stanford.edu> wrote: > > Interesting. I didn't think to use dump to check differences. > > > > Another followup question. After using dump on some simple if statements, > > I've noticed that all blocks induce this LineNumberNode which is messing > up > > the equality. > > Is there a way to ignore these nodes in the equality check? They show up > in > > any kind of block statement (function, if, etc) > > > > May I ask what do you need the equality of expressions for? It doesn't > sound like a too useful concept. There can be expressions that are > equal but have different side effects due to the variables they > capture (try constructing `Expr(:call, :push!, [1, 2], 1)` twice and > eval/compare them). There can also be expressions that are equivalant > but appears differently. > > In general, I never find `==` of expressions too useful. When > processing it, you can just ignore the line number nodes if you don't > care too much about debug info (also see base/docs/Docs.jl for some > example of stripping unwanted part from a expression). There's also > MacroTools.jl which provides a nice way to process expressions. > > > eg: > > > > dump(:(if true 1 else 0 end)) > > > > Expr > > > > head: Symbol if > > > > args: Array(Any,(3,)) > > > > 1: Bool true > > > > 2: Expr > > > > head: Symbol block > > > > args: Array(Any,(2,)) > > > > 1: LineNumberNode > > > > file: Symbol none > > > > line: Int64 1 > > > > 2: Int64 1 > > > > typ: Any > > > > 3: Expr > > > > head: Symbol block > > > > args: Array(Any,(2,)) > > > > 1: LineNumberNode > > > > file: Symbol none > > > > line: Int64 1 > > > > 2: Int64 0 > > > > typ: Any > > > > typ: Any > > > > > > dump(Expr(:if, true, Expr(:block, 0), Expr(:block,1))) > > > > Expr > > > > head: Symbol if > > > > args: Array(Any,(3,)) > > > > 1: Bool true > > > > 2: Expr > > > > head: Symbol block > > > > args: Array(Any,(1,)) > > > > 1: Int64 0 > > > > typ: Any > > > > 3: Expr > > > > head: Symbol block > > > > args: Array(Any,(1,)) > > > > 1: Int64 1 > > > > typ: Any > > > > typ: Any > > > > > > They're the same minus LineNumberNodes, because block type expressions > > always create those things. > > > > > > On Wednesday, December 9, 2015 at 7:21:55 AM UTC-8, STAR0SS wrote: > >> > >> You can also use dump() on your expressions to see how they differ > >> exactly. The normal printing doesn't really show you much. > -- Erik Schnetter <schnet...@gmail.com> http://www.perimeterinstitute.ca/personal/eschnetter/
