Function alignedHandler

src/environments/array.ts:701–786

(context: EnvContextLike, args: AnyParseNode[])

// Convenience function for align, align*, aligned, alignat, alignat*, alignedat.
const alignedHandler = function(context: EnvContextLike, args: AnyParseNode[]) {
    if (!context.envName.includes("ed")) {
        validateAmsEnvironmentContext(context);
    }
    const cols: AlignSpec[] = [];
    const isSplit = context.envName === "split";
    const res = parseArray(context.parser,
        {
            cols,
            addJot: true,
            autoTag: isSplit ? undefined : getAutoTag(context.envName),
            emptySingleRow: true,
            colSeparationType: context.envName.includes("at") ? "alignat" : "align",
            maxNumCols: isSplit ? 2 : undefined,
            leqno: context.parser.settings.leqno,
        },
        "display"
    );

    // Determining number of columns.
    // 1. If the first argument is given, we use it as a number of columns,
    //    and makes sure that each row doesn't exceed that number.
    // 2. Otherwise, just count number of columns = maximum number
    //    of cells in each row ("aligned" mode -- isAligned will be true).
    //
    // At the same time, prepend empty group {} at beginning of every second
    // cell in each row (starting with second cell) so that operators become
    // binary.  This behavior is implemented in amsmath's \start@aligned.
    let numMaths = 0;
    let numCols = 0;
    const emptyGroup: ParseNode<"ordgroup"> = {
        type: "ordgroup",
        mode: context.mode,
        body: [],
    };
    if (args[0] && args[0].type === "ordgroup") {
        let arg0 = "";
        for (let i = 0; i < args[0].body.length; i++) {
            const textord = assertNodeType(args[0].body[i], "textord");
            arg0 += textord.text;
        }
        numMaths = Number(arg0);
        numCols = numMaths * 2;
    }
    const isAligned = !numCols;
    res.body.forEach(function(row) {
        for (let i = 1; i < row.length; i += 2) {
            // Modify ordgroup node within styling node
            const styling = assertNodeType(row[i], "styling");
            const ordgroup = assertNodeType(styling.body[0], "ordgroup");
            ordgroup.body.unshift(emptyGroup);
        }
        if (!isAligned) { // Case 1
            const curMaths = row.length / 2;
            if (numMaths < curMaths) {
                throw new ParseError(
                    "Too many math in a row: " +
                    `expected ${numMaths}, but got ${curMaths}`,