I want to test the expression ``` macroexpand(:@fastmath :+) ```
where `:+` is a symbol, not a function. I wasn't able to determine the difference. I used both `info` and `dump`, and my LHS (the result of the expression above) and what I constructed manually looked identical, and in the REPL, the epression ``` macroexpand(:@fastmath :+) == :(:+) ``` yields `true`. In `test/fastmath.jl`, it didn't. (It works fine for five other expressions that are currently being tested.) Anyway -- my point being that it can be quite useful to compare expressions, even if the exact value might change over time. Since Julia's macros are all about manipulating expressions, having ways to output, serialize, load, compare, and treat them like any other data makes totally sense. -erik On Wed, Dec 9, 2015 at 4:05 PM, Yichao Yu <yyc1...@gmail.com> wrote: > On Wed, Dec 9, 2015 at 3:57 PM, Erik Schnetter <schnet...@gmail.com> > wrote: > > 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. > > What's the difference between REPL and test script? > > julia -f -e 'println(macroexpand(:(@fastmath +)) == > :(Base.FastMath.add_fast))' > true > > > > > > -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/ > -- Erik Schnetter <schnet...@gmail.com> http://www.perimeterinstitute.ca/personal/eschnetter/
