funcs.h

/* symbol table */
struct symbol {				/* a variable name */
	char *name;
	double value;
	struct ast *func;		/* stmt for the function */
	struct symlist *syms;		/* list of dummy args */
};

/* simple symtab of fixed size */
#define NHASH 9997
struct symbol symtab[NHASH];
struct symbol *lookup(char*);

/* list of symbols, for an argument list */
struct symlist {
	struct symbol *sym;
	struct symlist *next;
};

struct symlist *newsymlist(struct symbol *sym, struct symlist *next);
void symlistfree(struct symlist *sl);

/* node types
 *	+ - * / |
 *	0-7 comparison ops
 *	M unary minus (negative)
 *	L statement list
 *	I IF statement
 *	W WHILE statement
 *	N symbol ref
 *	= assignment
 *	S list of symbols
 *	F built in function call
 *	C user function call
 */
enum bifs {				/* built-in functions type */
	B_sqrt = 1,
	B_exp,
	B_log,
	B_sin,
	B_cos,
	B_print
};

/* nodes in the Abstract Syntax Tree */
/* all have common initial nodetype */
struct ast {
	int nodetype;
	struct ast *l;
	struct ast *r;
};

struct fncall {				/* built-in function */
	int nodetype;			/* type F */
	struct ast *l;
	enum bifs functype;
};

struct ufncall {			/* user function */
	int nodetype;			/* type C */
	struct ast *l;			/* list of arguments */
	struct symbol *s;
};

struct flow {
	int nodetype;			/* type I or W */
	struct ast *cond;		/* condition */
	struct ast *tl;			/* then or do list */
	struct ast *el;			/* optional else list */
};

struct numval {
	int nodetype;			/* type K */
	double number;
};

struct symref {
	int nodetype;			/* type N */
	struct symbol *s;
};

struct symasgn {
	int nodetype;			/* type = */
	struct symbol *s;
	struct ast *v;			/* value */
};

// build an AST
struct ast *newast(int nodetype, struct ast *l, struct ast *r);
struct ast *newcmp(int cmptype, struct ast *l, struct ast *r);
struct ast *newfunc(int functype, struct ast *l);
struct ast *newcall(struct symbol *s, struct ast *l);
struct ast *newref(struct symbol *s);
struct ast *newasgn(struct symbol *s, struct ast *v);
struct ast *newnum(double d);
struct ast *newflow(int nodetype, struct ast *cond, struct ast *tl, struct ast *tr);

// define a function
void dodef(struct symbol *name, struct symlist *syms, struct ast *stmts);

// call to built-in or user-defined function
static double callbuiltin(struct fncall*);
static double calluser(struct ufncall*);

// evaluate an AST, return the result of calculation
double eval(struct ast *);

// delete and free an AST recursively
void treefree(struct ast *);

// interface to the lexer
void yyerror(char *s, ...);
int yywrap();