# For fun: parsing nested decision chains for GDL3 / Task Planning

**Category:** [BMM/Expressions](https://discourse.openehr.org/c/bmm-el/60)
**Created:** 2022-02-21 21:56 UTC
**Views:** 482
**Replies:** 0
**URL:** https://discourse.openehr.org/t/for-fun-parsing-nested-decision-chains-for-gdl3-task-planning/2385

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## Post #1 by @thomas.beale

Mainly for language geeks, I have the following parsing in my development Antlr4 Expression Language parser.
Geek clinicians like @joostholslag, @siljelb , @varntzen might or might not find it interesting. (You have to pretend you are an oncologist to even potentially be excited).

```
Result :=
    choice in
        ================================================================================
        not metastatic:     choice in
                                ========================================================================
                                molecular_subtype matches
                                    {#luminal_B_HER2_negative, #triple_negative}
                                and
                                (tnm_t matches {"1b", "1c"} or tnm_n > 0):     #taxanes,
                                ------------------------------------------------------------------------
                                molecular_subtype = #luminal_A and
                                (tnm_t ≥ 3 or tnm_n ≥ 2 or tnm_g ≥ 3):         #anthracyclines,
                                ------------------------------------------------------------------------
                                molecular_subtype = #luminal_B_HER2_positive and
                                (tnm_t matches {"1b", "1c"} and tnm_n = 0)
                                or
                                molecular_subtype = #HER2_positive and
                                (tnm_t = "1b" and tnm_n = 0):                  #paditaxel_trastuzumab
                                ========================================================================
                            ;,
        --------------------------------------------------------------------------------
        *:                  choice in
                                =====================
                                yyy:        aaa,
                                ---------------------
                                xxx:        bbb,
                                ---------------------
                                *:          ccc
                                =====================
                            ;
        =================================================================================
    ;
```

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**Canonical:** https://discourse.openehr.org/t/for-fun-parsing-nested-decision-chains-for-gdl3-task-planning/2385
**Original content:** https://discourse.openehr.org/t/for-fun-parsing-nested-decision-chains-for-gdl3-task-planning/2385