/*
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");
}
}