Excel LAMBDA RPN Programming Challenge

Hi All: There is a website called rosettacode.org (currently offline) that is an archive of the same problem solved in large number of computer-languages( approximately 96 – listed below) . E...

excel

Formulas and Functions

LBROWN7

Brass Contributor

Oct 12, 2023

Below is my solution to the RPN Programming problem.

It works in Sheets. But returns a CALC error in Excel.

I suspect my problem is with the SCAN function in Excel which differs from what I expect/understand.

=LAMBDA(rpn_string,
    LET(
        _100, "RPN Calculator: https://www.rosettacode.org/wiki/Parsing/RPN_calculator_algorithm",
        SPLIT2_L, LAMBDA(string, delimiters,
            LET(
                _0, "SPLIT",
                _00, "Equivalent of Google Sheets Split funciton",
                _10, "with 'split by each' set to true ",
                _20, "see Google Sheets SPLIT documentation",
                _30, "",
                chars, MAKEARRAY(1, LEN(string), LAMBDA(ROW, COL, MID(string, COL, 1))),
                result, REDUCE(
                    "",
                    chars,
                    LAMBDA(acc, cv,
                        LET(
                            acclen, ROWS(acc),
                            isdelim, LAMBDA(v, ISNUMBER(FIND(v, delimiters))),
                            concat2lastrow, LAMBDA(update,
                                MAKEARRAY(
                                    acclen,
                                    1,
                                    LAMBDA(row, col, INDEX(acc, row, col) & IF(row = acclen, update, ""))
                                )
                            ),
                            addblankrow, LAMBDA(IF(INDEX(acc, acclen, 1) = "", acc, VSTACK(acc, ""))),
                            new_acc, IF(isdelim(cv), addblankrow(), concat2lastrow(cv)),
                            new_acc
                        )
                    )
                ),
                MAP(TOROW(result), LAMBDA(v, IF(ISNUMBER(v + 0), (v + 0), v)))
            )
        ),
        Lpad_L, LAMBDA(str, out_len, IF(LEN(str) < out_len, REPT(" ", out_len - LEN(str)), "") & str),
        expr_L, LAMBDA(op, x, y, CHOOSE(FIND(op, "+-*/^"), y + x, y - x, y * x, y / x, y ^ x)),
        tokens_v, SPLIT2_L(rpn_string, " "),
        parse_rpm_m, SCAN(
            "",
            tokens_v,
            LAMBDA(acc_v, c,
                IF(
                    ISNUMBER(c),
                    (IF(acc_v = "", HSTACK(c), VSTACK(acc_v, c))),
                    LET(
                        stack_rows, ROWS(acc_v),
                        expression, expr_L(c, INDEX(acc_v, stack_rows), INDEX(acc_v, stack_rows - 1)),
                        IF(
                            stack_rows - 2 = 0,
                            expression,
                            VSTACK(
                                MAKEARRAY(stack_rows - 2, 1, LAMBDA(r, c, INDEX(acc_v, r, c))),
                                expression
                            )
                        )
                    )
                )
            )
        ),
        result_1, TRANSPOSE(parse_rpm_m),
        result_2, MAP(
            SEQUENCE(COLUMNS(tokens_v)),
            LAMBDA(i, HSTACK(" [ " & Lpad_L(i, 2) & " ] " & INDEX(tokens_v, i), INDEX(result_1, i)))
        ),
        result_3, VSTACK(
            {"POSTFIX  EVALUATOR "},
            HSTACK("POSTFIX" & ":", TRIM(rpn_string)),
            HSTACK("RESULT" & ":", TRIM(INDEX(result_1, ROWS(result_1)))),
            {" ", " "},
            {"STEPS", "STACK  "},
            result_2
        ),
        result_4, MAP(result_3, LAMBDA(c, IF(ISERROR(c), "", c))),
        result_4
    )
)("3 4 2 * 1 5 - 2 3 ^ ^ / +")

Below is the output

POSTFIX EVALUATOR
POSTFIX:	3 4 2 * 1 5 - 2 3 ^ ^ / +
RESULT:	3.00012207

STEPS	STACK
[ 1 ] 3	3
[ 2 ] 4	3	4
[ 3 ] 2	3	4	2
[ 4 ] *	3	8
[ 5 ] 1	3	8	1
[ 6 ] 5	3	8	1	5
[ 7 ] -	3	8	-4
[ 8 ] 2	3	8	-4	2
[ 9 ] 3	3	8	-4	2	3
[ 10 ] ^	3	8	-4	8
[ 11 ] ^	3	8	65536
[ 12 ] /	3	0.0001220703125
[ 13 ] +	3.00012207

SergeiBaklan

MVP

Oct 13, 2023

LBROWN7

rpn = LAMBDA(str,
    LET(
        arr, TEXTSPLIT(str, " "),
        operand, LAMBDA(op, pair,
            LET(
                a, --INDEX(pair, 1, 1),
                b, --INDEX(pair, 1, 2),
                SWITCH( op,
                    "*", a*b,
                    "-", a-b,
                    "^", a^b,
                    "/", a/b,
                    "+", a+b
                )
            )
        ),
        operation, LAMBDA(a,v,
            IF( ISNUMBER(--v),
                HSTACK(a, v),
                HSTACK(DROP(a,,-2), operand(v, (TAKE(a,,-2))) )
            ) ),
        REDUCE( "Result:", arr, operation)
))

SergeiBaklan

MVP

Oct 13, 2023

LBROWN7

As variant

rpn = LAMBDA(str,
LET(
    arr, TEXTSPLIT(str, " "), 
    mpl, LAMBDA(pair, INDEX(pair,1,1)*INDEX(pair,1,2) ),
    sbs, LAMBDA(pair, INDEX(pair,1,1)-INDEX(pair,1,2) ),
    pow, LAMBDA(pair, INDEX(pair,1,1)^INDEX(pair,1,2) ),
    div, LAMBDA(pair, INDEX(pair,1,1)/INDEX(pair,1,2) ),
    pls, LAMBDA(pair, INDEX(pair,1,1)+INDEX(pair,1,2) ),
    DROP(
    REDUCE(0, arr,
    LAMBDA(a,v,
        IF( ISNUMBER(--v), HSTACK(a,v),
        IF( v="*", HSTACK( DROP(a,,-2), mpl( TAKE(a,,-2) )),
        IF( v="-", HSTACK( DROP(a,,-2), sbs( TAKE(a,,-2) )),
        IF( v="^", HSTACK( DROP(a,,-2), pow( TAKE(a,,-2) )),
        IF( v="/", HSTACK( DROP(a,,-2), div( TAKE(a,,-2) )),
        IF( v="+", HSTACK( DROP(a,,-2), pls( TAKE(a,,-2) )),
         ))))))
    ) ), ,1 )
))

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Excel LAMBDA RPN Programming Challenge

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