chapter 8

CMakeLists.txt

@@ -0,0 +1,8 @@
+cmake_minimum_required(VERSION 3.12)
+project(crisp C)
+
+set(CMAKE_C_STANDARD 99)
+
+add_executable(main main.c mpc.c eval.c eval.h)
+
+target_link_libraries(main edit)

README.md

@@ -1,3 +1,5 @@
 # crisp
 
-lisp but crispier
+lisp but crispier
+
+follows the book http://www.buildyourownlisp.com

eval.c

@@ -0,0 +1,77 @@
+//
+// Created by red on 05/12/19.
+//
+
+#include "eval.h"
+
+// create number type cval
+cval cval_num(long x) {
+  cval v;
+  v.type = CVAL_NUM;
+  v.num = x;
+  return v;
+}
+
+// create error type cval
+cval cval_err(int x){
+  cval v;
+  v.type = CVAL_ERR;
+  v.err = x;
+  return v;
+}
+
+
+void cval_print(cval v) {
+  switch (v.type) {
+  case CVAL_NUM: printf("%li", v.num); break;
+  case CVAL_ERR: {
+    switch (v.err) {
+    case CERR_DIV_ZERO: printf("Error: Division by zero"); break;
+    case CERR_BAD_OP: printf("Error: Invalid operator"); break;
+    case CERR_BAD_NUM: printf("Error: Invalid number"); break;
+    default: break;
+    }
+  }
+  default: break;
+  }
+}
+
+void cval_println(cval v) {
+  cval_print(v);
+  putchar('\n');
+}
+
+cval eval_op(cval x, char* op, cval y) {
+  if (x.type == CVAL_ERR) {return x;}
+  if (y.type == CVAL_ERR) {return y;}
+  switch (*op) {
+  case '+': return cval_num(x.num + y.num);
+  case '-': return cval_num(x.num - y.num);
+  case '*': return cval_num(x.num * y.num);
+  //return error
+  case '/': return y.num == 0 ? cval_err(CERR_DIV_ZERO) : cval_num(x.num / y.num);
+  default: return cval_err(CERR_BAD_OP);
+  }
+}
+
+cval eval(mpc_ast_t* t) {
+
+  if (strstr(t->tag, "number")) {
+    errno = 0;
+    long x = strtol(t->contents, NULL, 10);
+    return errno != ERANGE ? cval_num(x) : cval_err(CERR_BAD_NUM);
+  }
+
+  // the operator is always the second child
+  char* op = t->children[1]->contents;
+  cval x = eval(t->children[2]);
+
+  // iterate over the remaining children and combine
+  int i = 3;
+  while (strstr(t->children[i]->tag, "expr")) {
+    x = eval_op(x, op, eval(t->children[i]));
+    i++;
+  }
+
+  return x;
+}

eval.h

@@ -0,0 +1,21 @@
+//
+// Created by red on 05/12/19.
+//
+
+
+#include "mpc.h"
+
+#ifndef CRISP_EVAL_H
+#define CRISP_EVAL_H
+typedef struct {
+  int type;
+  long num;
+  int err;
+} cval;
+enum { CVAL_NUM, CVAL_ERR };
+enum { CERR_DIV_ZERO, CERR_BAD_OP, CERR_BAD_NUM };
+cval eval(mpc_ast_t* t);
+void cval_print(cval v);
+void cval_println(cval v);
+
+#endif //CRISP_EVAL_H

main.c

@@ -0,0 +1,54 @@
+//
+// Created by red on 03/12/19.
+//
+
+#include <stdio.h>
+#include <editline/readline.h>
+#include <editline/history.h>
+#include <stdlib.h>
+#include "mpc.h"
+#include "eval.h"
+
+#pragma clang diagnostic ignored "-Wmissing-noreturn"
+
+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* Crisp = mpc_new("crisp");
+
+  mpca_lang(MPCA_LANG_DEFAULT,
+      " number   : /-?[0-9]+/ ;"
+      " operator : '+' | '-' | '*' | '/' ;"
+      " expr     : <number> | '(' <operator> <expr>+ ')' ;"
+      " crisp    : /^/ <operator> <expr>+ /$/ ;",
+      Number, Operator, Expr, Crisp);
+
+  puts("Crisp v.0.0.1");
+  puts("Press Ctrl-C to exit\n");
+
+  for (;;) {
+
+    char* input = readline("crisp> ");
+    add_history(input);
+
+    // attempt to parse input
+    mpc_result_t r;
+    if (mpc_parse("<stdin>", input, Crisp, &r)) {
+
+      cval result = eval(r.output);
+      cval_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, Crisp);
+  return EXIT_SUCCESS;
+}