(Somewhat adapted) code and solutions from the book "Build Your Own Lisp"
http://www.buildyourownlisp.com
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142 lines
3.5 KiB
142 lines
3.5 KiB
#include <stdio.h>
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#include <stdlib.h>
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#include "../mpc/mpc.h"
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/* If we are on Windows compile these functions */
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#ifdef _WIN32
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#include <string.h>
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#include <assert.h>
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static char buffer[2048];
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/* Fake readline function */
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char* readline(char* prompt) {
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fputs(prompt, stdout);
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fgets(buffer, 2048, stdin);
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char* cpy = malloc(strlen(buffer)+1);
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assert(cpy != NULL)
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strcpy(cpy, buffer);
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cpy[strlen(cpy)-1] = '\0';
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return cpy;
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}
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/* Fake add_history function */
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void add_history(char* unused) {}
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/* Otherwise include the editline headers
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could use __APPLE__ for detection of OSX */
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#else
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#include <editline/readline.h>
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#endif
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long min(long x, long y) {
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if (x <= y) {
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return x;
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} else {
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return y;
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}
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}
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long max(long x, long y) {
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if (x >= y) {
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return x;
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} else {
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return y;
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}
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}
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/* Use operator string to see which operation to perform */
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long eval_op(long x, char* op, long y) {
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if (strcmp(op, "+") == 0) {return x + y;}
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if (strcmp(op, "-") == 0) {return x - y;}
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if (strcmp(op, "*") == 0) {return x * y;}
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if (strcmp(op, "/") == 0) {return x / y;}
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if (strcmp(op, "%") == 0) {return x % y;}
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if (strcmp(op, "^") == 0) {return pow(x, y);}
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if (strcmp(op, "min") == 0) {return min(x, y);}
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if (strcmp(op, "max") == 0) {return max(x, y);}
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return 0;
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}
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long eval(mpc_ast_t* t) {
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/* If tagged as number return it directly */
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if (strstr(t->tag, "number")) {
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return atoi(t->contents);
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}
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/* The operator is always second child */
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char* op = t->children[1]->contents;
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/* We store the third children in x */
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long x = eval(t->children[2]);
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/* Iterate the remaining children and combining */
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unsigned int i = 3;
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while (strstr(t->children[i]->tag, "expr")) {
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x = eval_op(x, op, eval(t->children[i]));
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i++;
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}
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return x;
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}
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int main(int argc, char const *argv[]) {
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/* Create some parsers */
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mpc_parser_t* Number = mpc_new("number");
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mpc_parser_t* Operator = mpc_new("operator");
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mpc_parser_t* Expr = mpc_new("expr");
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mpc_parser_t* Lispy = mpc_new("lispy");
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/* Define them with the following language */
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mpca_lang(MPCA_LANG_DEFAULT,
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" \
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number : /-?[0-9]+/ ; \
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operator : '+' | '-' | '*' | '/' | '%' | '^' | \
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\"min\" | \"max\" ; \
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expr : <number> | '(' <operator> <expr>+ ')' ; \
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lispy : /^/ <operator> <expr>+ /$/ ; \
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",
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Number, Operator, Expr, Lispy);
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/* Print version and exit information */
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puts("Lispy version 0.0.0.0.3");
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puts("Press Ctrl+c to exit\n");
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/* In a never ending loop */
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while (1) {
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/* Output our prompt and get input */
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char* input = readline("lispy> ");
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/* Add input to history */
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add_history(input);
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/* Attempt to parse the user input */
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mpc_result_t r;
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if (mpc_parse("<stdin>", input, Lispy, &r)) {
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/* On success evaluate the user input */
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long result = eval(r.output);
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printf("%li\n", result);
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mpc_ast_delete(r.output);
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} else {
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/* Otherwise print the error */
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mpc_err_print(r.error);
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mpc_err_delete(r.error);
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}
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/* Free retrieved input */
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free(input);
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}
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/* Undefine and delete our parsers */
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mpc_cleanup(4, Number, Operator, Expr, Lispy);
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return 0;
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}
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