inplace accum.jl

using MacroTools

symchar(symb::Symbol) = symb, 'N'

function symchar(ex::Expr)
    if ex.head == symbol("'")
        return ex.args[1], 'C'
    elseif ex.head == :(.')
        return ex.args[1], 'T'
    else
        throw(Error("invalid macro usage"))
    end
end

macro into_plus!(ex)
    α = 1.0
    last_match = nothing
    matched = false
    match = @match ex begin
           (C_ += A_ * B_) => (C, A, B)
    end
    if match != nothing
        last_match = match
        matched = true
    end
    match = @match ex begin
            (C_ += α_ * A_ * B_) => (C, A, B, α)
        end
    if match != nothing
        last_match = match
        matched = true
        α = match[4]
    end

    if last_match != nothing
         C, A_s, B_s = last_match[1], last_match[2], last_match[3]
         A, A_char = symchar(A_s)
         B, B_char = symchar(B_s)
        quote BLAS.gemm!($A_char, $B_char, $α, $A, $B, 1.0, $C) end
    else
        throw(ArgumentError("invalid macro usage"))
    end
end