# multline inside an item

Is there a way to use a multline inside an \item element of enumerate WITHOUT a new line between the index of list and the formula?

 \begin{enumerate}[i.]
\item $checkorder( (\lambda,\lambda,\lambda) ) \triangleq true$
\item \begin{multline*}$$checkorder( (a,(u,U_1,U_2),(v,V_1,V_2)) ) \triangleq \\ (u = \lambda \vee u \leq_A a) \wedge (v = \lambda \vee a \leq_A v) \wedge \\ checkorder(U_1) \, \wedge checkorder(U_2) \wedge checkorder(V_1) \wedge checkorder(V_2)$$
\end{multline*}
\item $checkorder(T) \triangleq false$ negli altri casi
\end{enumerate}


this is what i have:

and this is what i would want:

-

The amsmath alignment environments are only for display math. But mathtools augments the available environments:

\documentclass[a4paper]{article}
\usepackage{mathtools,enumerate,amssymb}
\begin{document}

\begin{enumerate}[i.]
\item $\mathit{checkorder}( (\lambda,\lambda,\lambda) ) \triangleq \mathit{true}$
\item $\begin{multlined}[t] \mathit{checkorder}( (a,(u,U_1,U_2),(v,V_1,V_2)) ) \triangleq \\ (u = \lambda \vee u \leq_A a) \wedge (v = \lambda \vee a \leq_A v) \wedge {} \\ \mathit{checkorder}(U_1) \wedge \mathit{checkorder}(U_2) \wedge \mathit{checkorder}(V_1) \wedge checkorder(V_2) \end{multlined}$
\item $\mathit{checkorder}(T) \triangleq \mathit{false}$ negli altri casi
\end{enumerate}
\end{document}


Notice a couple of refinements: long function names should be inside \mathit, to get a better looking font in this case; the \wedge before \\ should be followed by {} to get correct spacing.

Never use $$ in LaTeX. - thanks! why never use$$ ? – tyranitar Feb 12 '12 at 11:52
See Why is $...$ preferable to ?. On this site appreciation for an answer is expressed by clicking on the upper arrow besides the text; usually, after a delay to see if other more useful answers come along, one accepts the better one. – egreg Feb 12 '12 at 12:08
+1 By the same rational, is it not more preferable to use $$...$$ instead of $...$ I reference Joseph Wright's comments in Are ( and ) preferable to \$? – cmhughes Feb 12 '12 at 17:14

I had a similar issue with \multline environment. So I came up with a forced solution. Here is what I did:

\item \abovedisplayskip-15pt
\belowdisplayskip\abovedisplayskip
\begin{setlength}{\multlinegap}{0pt}
\begin{multline*}
2(x^2y-2xy^3+6xy)-3(-5xy+3x^2y\\-7xy^3)
+5(xy^3-xy+x^2y)
\end{multline*}
\end{setlength}


Of course, egreg's solution is by far the best and mine is was just out of desperation in finding an immediate solutions. I know that my code above is not the best but hey it solved my problem. I have decided to implement egreg's answer into my code as it seems to better and more concise.

-