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/*
   Copyright (C) 2019-2020 Andreas Franz Borchert
                           Michael Christian Lehn
   ----------------------------------------------------------------------------
   The Astl Library for ULMasm is free software; you can redistribute it
   and/or modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either version
   2 of the License, or (at your option) any later version.

   The Astl Library for ULMasm is distributed in the hope that it will be
   useful, but WITHOUT ANY WARRANTY; without even the implied warranty
   of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with this library; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

sub getValue(node) {
    if (exists node.value) {
        return node.value;
    }
    println("unknown identifier " & node.ident);
    exit(1);
}

attribution rules {

    // leaf nodes have an immediate value
    ("integer" int) as node -> post {
        node.value = int;
    }

    // setup an empty symtab
    ("calc" *) as unit -> pre {
        unit.symtab = {};
    }


    // resove identifiers if possible, otherwise use name as value
    ("identifier" ident) as node in ("calc" *) as unit -> post {
        var name = gentext(ident);

        if (exists unit.symtab{name}) {
            node.value = unit.symtab{name};
        } else {
            node.ident = name;
        }
    }

    // evaluate sub nodes
    ("unary-" op) as node -> post {
        node.value = -getValue(op);
    }
    ("+" op1 op2) as node -> post {
        node.value = getValue(op1) + getValue(op2);
    }
    ("-" op1 op2) as node -> post {
        node.value = getValue(op1) - getValue(op2);
    }
    ("*" op1 op2) as node -> post {
        node.value = getValue(op1) * getValue(op2);
    }
    ("/" op1 op2) as node -> post {
        node.value = getValue(op1) div getValue(op2);
    }
    ("%" op1 op2) as node -> post {
        node.value = getValue(op1) mod getValue(op2);
    }

    // print original expressions
    ("expression" *) as node -> pre {
        println("> ", gentext(node));
    }
    // expression now has result
    ("expression" expr) as node -> post {
        println(expr.value);
    }

    // print original assignment
    ("=" *) as node -> pre {
        println("> ", gentext(node));
    }
    // assignment done, show result
    ("=" ident expr) as assign in ("calc" *) as unit -> post {
        var name = gentext(ident);
        unit.symtab{name} = getValue(expr);
        println(name, " = ", expr.value, "\n");
    }
}