visitor_ex

#!/bin/bash
#
# A simple example to demo implementation of an expression calc.  (Not
# entirely an indented use case of the library.)

readonly DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
. ${DIR}/../gobash


function Val() {
        local -r val="${1}"

        make_ "$FUNCNAME" \
              "val" "${val}"
}

function Val_accept() {
        local val="${1}"
        $val val
}

function AddExpr() {
        local -r l="${1}"
        local -r r="${2}"

        make_ "$FUNCNAME" \
              "l" "${l}" \
              "r" "${r}"
}

function AddExpr_accept() {
        local -r e="${1}"
        local -r v="${2}"

        $v visit_add "$e"
}

function MulExpr() {
        local -r l="${1}"
        local -r r="${2}"

        make_ "$FUNCNAME" \
              "l" "${l}" \
              "r" "${r}"
}

function MulExpr_accept() {
        local -r e="${1}"
        local -r v="${2}"

        $v visit_mul "$e"
}

function SubExpr() {
        local -r l="${1}"
        local -r r="${2}"

        make_ "$FUNCNAME" \
              "l" "${l}" \
              "r" "${r}"
}

function SubExp_accept() {
        local -r e="${1}"
        local -r v="${2}"

        $v visit_sub "$e"
}

function DivExpr() {
        local -r l="${1}"
        local -r r="${2}"

        make_ "$FUNCNAME" \
              "l" "${l}" \
              "r" "${r}"
}

function DivExpr_accept() {
        local -r e="${1}"
        local -r v="${2}"

        $v visit_div "$e"
}

function Visitor() {
        make_ "$FUNCNAME"
}

function Visitor_visit_add() {
        local -r v="${1}"
        local -r e="${2}"

        local lv=$($($e l) accept "$v")
        local rv=$($($e r) accept "$v")
        math_calc "${lv} + ${rv}"
}

function Visitor_visit_mul() {
        local -r v="${1}"
        local -r e="${2}"

        local lv=$($($e l) accept "$v")
        local rv=$($($e r) accept "$v")
        math_calc "${lv} * ${rv}"
}

function Visitor_visit_sub() {
        local -r v="${1}"
        local -r e="${2}"

        local lv=$($($e l) accept "$v")
        local rv=$($($e r) accept "$v")
        math_calc "${lv} - ${rv}"
}

function Visitor_visit_div() {
        local -r v="${1}"
        local -r e="${2}"

        local lv=$($($e l) accept "$v")
        local rv=$($($e r) accept "$v")
        math_calc "${lv} / ${rv}"
}

# (5 + 3) * (10 / 2)
l=$(AddExpr "$(Val 5)" "$(Val 3)")
r=$(DivExpr "$(Val 10)" "$(Val 2)")
root=$(MulExpr "$l" "$r")

v=$(Visitor)
$root accept "$v"