--- stack/stack.c 2002/02/05 12:14:42 1.29 +++ stack/stack.c 2002/02/05 23:00:42 1.33 @@ -58,6 +58,7 @@ typedef struct { stackitem *head; /* Head of the stack */ hashtbl symbols; /* Hash table of all variable bindings */ + int err; /* Error flag */ } environment; /* A type for pointers to external functions */ @@ -178,10 +179,10 @@ new_symbol= hash(env->symbols, in_string); new_value->content.ptr= *new_symbol; - if(new_value->content.ptr==NULL) { /* If symbol was undefined */ + if(*new_symbol==NULL) { /* If symbol was undefined */ /* Create a new symbol */ - *new_symbol= malloc(sizeof(symbol)); + (*new_symbol)= malloc(sizeof(symbol)); (*new_symbol)->val= NULL; /* undefined value */ (*new_symbol)->next= NULL; (*new_symbol)->id= malloc(strlen(in_string)+1); @@ -254,7 +255,7 @@ } /* Print newline. */ -extern void nl() +extern void nl(environment *env) { printf("\n"); } @@ -348,6 +349,28 @@ return out_item; } +/* Recall a value from a symbol, if bound */ +extern void rcl(environment *env) +{ + value *val; + + if(env->head == NULL) { + printerr("Stack empty"); + return; + } + + if(env->head->item->type!=symb) { + printerr("Not a symbol"); + return; + } + val=((symbol *)(env->head->item->content.ptr))->val; + if(val == NULL){ + printerr("Unbound variable"); + return; + } + toss(env); /* toss the symbol */ + push_val(&(env->head), val); /* Return its bound value */ +} /* If the top element is a symbol, determine if it's bound to a function value, and if it is, toss the symbol and execute the @@ -392,9 +415,6 @@ return; } -/* push(&(env->head), copy(env->head)); */ -/* swap(env); */ -/* toss(env); */ } /* Make a list. */ @@ -624,6 +644,21 @@ toss(env); } +/* List all defined words */ +extern void words(environment *env) +{ + symbol *temp; + int i; + + for(i= 0; isymbols[i]; + while(temp!=NULL) { + printf("%s\n", temp->id); + temp= temp->next; + } + } +} + int main() { environment myenv;