Created
May 31, 2014 15:27
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| #include "mpc.h" | |
| #include <editline/readline.h> | |
| enum { LERR_DIV_ZERO, LERR_BAD_OP, LERR_BAD_NUM }; | |
| enum { LVAL_NUM, LVAL_ERR }; | |
| typedef struct { | |
| int type; | |
| long num; | |
| int err; | |
| } lval; | |
| lval lval_num(long x) { | |
| lval v; | |
| v.type = LVAL_NUM; | |
| v.num = x; | |
| return v; | |
| } | |
| lval lval_err(int x) { | |
| lval v; | |
| v.type = LVAL_ERR; | |
| v.err = x; | |
| return v; | |
| } | |
| void lval_print(lval v) { | |
| switch (v.type) { | |
| case LVAL_NUM: | |
| printf("%li", v.num); | |
| break; | |
| case LVAL_ERR: | |
| if (v.err == LERR_DIV_ZERO) { printf("Error: Division By Zero!"); } | |
| if (v.err == LERR_BAD_OP) { printf("Error: Invalid Operator!"); } | |
| if (v.err == LERR_BAD_NUM) { printf("Error: Invalid Number!"); } | |
| break; | |
| } | |
| } | |
| void lval_println(lval v) { lval_print(v); putchar('\n'); } | |
| lval eval_op(lval x, char* op, lval y) { | |
| if (x.type == LVAL_ERR) { return x; } | |
| if (y.type == LVAL_ERR) { return y; } | |
| if (strcmp(op, "+") == 0) { return lval_num(x.num + y.num); } | |
| if (strcmp(op, "-") == 0) { return lval_num(x.num - y.num); } | |
| if (strcmp(op, "*") == 0) { return lval_num(x.num * y.num); } | |
| if (strcmp(op, "/") == 0) { | |
| return y.num == 0 ? lval_err(LERR_DIV_ZERO) : lval_num(x.num / y.num); | |
| } | |
| return lval_err(LERR_BAD_OP); | |
| } | |
| lval eval(mpc_ast_t* t) { | |
| if (strstr(t->tag, "number")) { | |
| errno = 0; | |
| long x = strtol(t->contents, NULL, 10); | |
| return errno != ERANGE ? lval_num(x) : lval_err(LERR_BAD_NUM); | |
| } | |
| char* op = t->children[1]->contents; | |
| lval x = eval(t->children[2]); | |
| int i = 3; | |
| while(strstr(t->children[i]->tag, "expr")) { | |
| x = eval_op(x, op, eval(t->children[i])); | |
| i++; | |
| } | |
| return x; | |
| } | |
| // compile with | |
| // $ cc -std=c99 -Wall error_handling.c mpc.c -ledit -lm -o error_handling | |
| int main(int argc, char** argv) { | |
| mpc_parser_t* Number = mpc_new("number"); | |
| mpc_parser_t* Operator = mpc_new("operator"); | |
| mpc_parser_t* Expr = mpc_new("expr"); | |
| mpc_parser_t* Lispy = mpc_new("lispy"); | |
| mpca_lang(MPCA_LANG_DEFAULT, | |
| " \ | |
| number : /-?[0-9]+/ ; \ | |
| operator : '+' | '-' | '*' | '/' ; \ | |
| expr : <number> | '(' <operator> <expr>+ ')' ; \ | |
| lispy : /^/ <operator> <expr>+ /$/ ; \ | |
| ", | |
| Number, Operator, Expr, Lispy); | |
| puts("Lispy Version 0.0.0.0.4"); | |
| puts("Press Ctrl+c to Exit\n"); | |
| while (1) { | |
| char* input = readline("lispy> "); | |
| add_history(input); | |
| mpc_result_t r; | |
| if (mpc_parse("<stdin>", input, Lispy, &r)) { | |
| lval result = eval(r.output); | |
| lval_println(result); | |
| mpc_ast_delete(r.output); | |
| } else { | |
| mpc_err_print(r.error); | |
| mpc_err_delete(r.error); | |
| } | |
| free(input); | |
| } | |
| mpc_cleanup(4, Number, Operator, Expr, Lispy); | |
| return 0; | |
| } |
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