Add source of chapter 07

chapter_07/Makefile

@@ -0,0 +1,13 @@
+MPC_DIR := ../mpc
+
+
+all: lispy
+
+
+%: %.c
+	cc -std=c11 -Wall $@.c ${MPC_DIR}/mpc.c -ledit -o $@
+
+
+.PHONY: clean
+clean:
+	rm -rf lispy

chapter_07/lispy.c

@@ -0,0 +1,119 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "../mpc/mpc.h"
+
+
+/* If we are on Windows compile these functions */
+#ifdef _WIN32
+#include <string.h>
+#include <assert.h>
+
+static char buffer[2048];
+
+/* Fake readline function */
+char* readline(char* prompt) {
+    fputs(prompt, stdout);
+    fgets(buffer, 2048, stdin);
+    char* cpy = malloc(strlen(buffer)+1);
+    assert(cpy != NULL)
+    strcpy(cpy, buffer);
+    cpy[strlen(cpy)-1] = '\0';
+    return cpy;
+}
+
+/* Fake add_history function */
+void add_history(char* unused) {}
+
+/* Otherwise include the editline headers
+   could use __APPLE__ for detection of OSX */
+#else
+#include <editline/readline.h>
+#endif
+
+
+/* Use operator string to see which operation to perform */
+long eval_op(long x, char* op, long y) {
+    if (strcmp(op, "+") == 0) {return x + y;}
+    if (strcmp(op, "-") == 0) {return x - y;}
+    if (strcmp(op, "*") == 0) {return x * y;}
+    if (strcmp(op, "/") == 0) {return x / y;}
+    return 0;
+}
+
+
+long eval(mpc_ast_t* t) {
+
+    /* If tagged as number return it directly */
+    if (strstr(t->tag, "number")) {
+        return atoi(t->contents);
+    }
+
+    /* The operator is always second child */
+    char* op = t->children[1]->contents;
+
+    /* We store the third children in x */
+    long x = eval(t->children[2]);
+
+    /* Iterate the remaining children and combining */
+    unsigned int i = 3;
+    while (strstr(t->children[i]->tag, "expr")) {
+        x = eval_op(x, op, eval(t->children[i]));
+        i++;
+    }
+
+    return x;
+}
+
+
+int main(int argc, char const *argv[])
+{
+    /* Create some parsers */
+    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");
+
+    /* Define them with the following language */
+    mpca_lang(MPCA_LANG_DEFAULT,
+        "                                                       \
+            number   : /-?[0-9]+/ ;                             \
+            operator : '+' | '-' | '*' | '/' ;                  \
+            expr     : <number> | '(' <operator> <expr>+ ')' ;  \
+            lispy    : /^/ <operator> <expr>+ /$/ ;             \
+        ",
+        Number, Operator, Expr, Lispy);
+
+    /* Print version and exit information */
+    puts("Lispy version 0.0.0.0.3");
+    puts("Press Ctrl+c to exit\n");
+
+    /* In a never ending loop */
+    while (1) {
+        /* Output our prompt and get input */
+        char* input = readline("lispy> ");
+
+        /* Add input to history */
+        add_history(input);
+
+        /* Attempt to parse the user input */
+        mpc_result_t r;
+        if (mpc_parse("<stdin>", input, Lispy, &r)) {
+            /* On success evaluate the user input */
+            long result = eval(r.output);
+            printf("%li\n", result);
+            mpc_ast_delete(r.output);
+        } else {
+            /* Otherwise print the error */
+            mpc_err_print(r.error);
+            mpc_err_delete(r.error);
+        }
+
+        /* Free retrieved input */
+        free(input);
+    }
+
+    /* Undefine and delete our parsers */
+    mpc_cleanup(4, Number, Operator, Expr, Lispy);
+
+    return 0;
+}