support parsing of a small subset of MathML

...let's see what can be done with it

src/math.jl

 
 """
-    parseMath(ast::VPtr)::Math
+    ast_is(ast::VPtr, what::Symbol)::Bool
+
+Helper for quickly recognizing kinds of ASTs
+"""
+ast_is(ast::VPtr, what::Symbol)::Bool = ccall(sbml(what), Cint, (VPtr,), ast) != 0
+
+"""
+    parse_math(ast::VPtr)::Math
 
 This attempts to parse out a decent Julia-esque ([`Math`](@ref) AST from a
 pointer to `ASTNode_t`.
 """
-function parseMath(ast::VPtr)::Math
-    @info "got $ast"
-    MathIdent("placeholder")
+function parse_math(ast::VPtr)::Math
+    if ast_is(ast, :ASTNode_isName) || ast_is(ast, :ASTNode_isConstant)
+        return MathIdent(get_string(ast, :ASTNode_getName))
+    elseif ast_is(ast, :ASTNode_isConstantNumber)
+        return MathVal(ccall_sbml(:ASTNode_getValue), Cdouble, (VPtr,), ast)
+    elseif ast_is(ast, :ASTNode_isFunction)
+        return MathApply(
+            get_string(ast, :ASTNode_getName),
+            [
+                parse_math(ccall(sbml(:ASTNode_getChild), VPtr, (VPtr, Cuint), ast, i - 1))
+                for i = 1:ccall(sbml(:ASTNode_getNumChildren), Cuint, (VPtr,), ast)
+            ],
+        )
+    elseif ast_is(ast, :ASTNode_isOperator)
+        return MathApply(
+            string(Char(ccall(sbml(:ASTNode_getCharacter), Cchar, (VPtr,), ast))),
+            [
+                parse_math(ccall(sbml(:ASTNode_getChild), VPtr, (VPtr, Cuint), ast, i - 1))
+                for i = 1:ccall(sbml(:ASTNode_getNumChildren), Cuint, (VPtr,), ast)
+            ],
+        )
+    else
+        @warn "unsupported math element at $ast"
+        return MathIdent("?unsupported?")
+    end
 end

src/readsbml.jl

@@ -236,7 +236,7 @@ function extractModel(mdl::VPtr)::Model
             end
 
             if ccall(sbml(:KineticLaw_isSetMath), Cint, (VPtr,), kl) != 0
-                math = parseMath(ccall(sbml(:KineticLaw_getMath), VPtr, (VPtr,), kl))
+                math = parse_math(ccall(sbml(:KineticLaw_getMath), VPtr, (VPtr,), kl))
             end
         end
 

src/structs.jl

@@ -79,7 +79,6 @@ Function application ("call by name", no tricks allowed) in mathematical express
 """
 struct MathApply <: Math
     fn::String
-    attributes::Dict{String,String}
     args::Vector{Math}
 end