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environment.c
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environment.c
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/* This file is part of Lithp.
Lithp is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
Lithp 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with lithp; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "cons.h"
#include "environment.h"
Cons* newEnvironment(Cons* parent)
{
return CONS(NEW_CONS_ATOM(parent), NIL);
}
// ( name . (variable))
// env => (parent (name . var) (name . var))
void newVariable(Cons* env, char* name, Atom* atom)
{
if(!env) {
ERROR("can't add variable to null environment", "");
return;
}
// look for an existing symbol by that name
while(CDR(env) && (env = CDRCONS(env))) {
if(strcmp(CAR(CARCONS(env))->value.symbol, name)==0) {
CDR(CARCONS(env)) = atom; // if we find it already, replace it
return;
}
}
// otherwise add a new one
Cons* pair = CONS(NEW_SYMBOL_ATOM(name), atom);
CDR(env) = NEW_CONS_ATOM(CONS(NEW_CONS_ATOM(pair),NIL));
}
Atom* lookupVariable(Cons* env, char* name)
{
Cons* parent = CARCONS(env);
while(CDR(env) && (env = CDRCONS(env))) {
Cons* pair = CARCONS(env); // (name . var)
if(strcmp(CAR(pair)->value.symbol, name) == 0) return CDR(pair);
}
if(parent) return lookupVariable(parent, name);
return 0;
}
void REGISTER_PRIMITIVE(Cons* env, char* name, LITHP_FUNCTION function, int special)
{
newVariable(env, name, NEW_PRIMITIVE_ATOM(function, special));
}