Shows optimizing parentheses in TeX output for a left-associative operator.

pretty_binary.js

PrettyMath_Binary_LeftAssoc(opsymbol) {
    let left = this.arglist[0].PrettyMath();
    let right = this.arglist[1].PrettyMath();

    // Use parentheses around the left child expression
    // if its operator precedence is less than this node's precedence.
    // If it is equal, assume left-associativity means parentheses are not needed.
    if (this.arglist[0].precedence < this.precedence) {
        left = '\\left(' + left + '\\right)';
    }

    // Use parentheses around the right child expression
    // if operator precedence is lower or equal.
    // Even if equal, parentheses are needed because we are
    // overriding left-associativity.
    if (this.arglist[1].precedence <= this.precedence) {
        right = '\\left(' + right + '\\right)';
    }

    return left + (opsymbol || this.optoken.text) + right;
}