Add source of chapter 08

chapter_08/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_08/lispy.c

@@ -0,0 +1,226 @@
+#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
+
+
+/* Declare new lval struct */
+typedef struct {
+    int type;
+    long num;
+    int err;
+} lval;
+
+
+/* Create enumeration of possible lval types */
+enum {LVAL_NUM, LVAL_ERR};
+
+
+/* Create enumeration of possible error types */
+enum {LERR_DIV_ZERO, LERR_BAD_OP, LERR_BAD_NUM};
+
+
+/* Create a new number of type lval */
+lval lval_num(long x) {
+    lval v;
+    v.type = LVAL_NUM;
+    v.num = x;
+    return v;
+}
+
+
+/* Create a new error type lval */
+lval lval_err(int x) {
+    lval v;
+    v.type = LVAL_ERR;
+    v.err = x;
+    return v;
+}
+
+
+/* Print an lval */
+void lval_print(lval v) {
+    switch (v.type) {
+        /* In the case the type is a number print it
+           Then break out of the switch */
+        case LVAL_NUM:
+            printf("%li", v.num);
+            break;
+        /* In the case the type is an error */
+        case LVAL_ERR:
+            /* Check what type of error it is & print it */
+            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;
+    }
+}
+
+
+/* Print an lval followed by a newline */
+void lval_println(lval v) {
+    lval_print(v);
+    putchar('\n');
+}
+
+
+long min(long x, long y) {
+    if (x <= y) {
+        return x;
+    } else {
+        return y;
+    }
+}
+
+
+long max(long x, long y) {
+    if (x >= y) {
+        return x;
+    } else {
+        return y;
+    }
+}
+
+
+/* Use operator string to see which operation to perform */
+lval eval_op(lval x, char* op, lval y) {
+
+    /* If either value is an error return it */
+    if (x.type == LVAL_ERR) {
+        return x;
+    }
+    if (y.type == LVAL_ERR) {
+        return y;
+    }
+
+    /* Otherwise do maths on the number values */
+
+    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) {
+        /* If second operand is zero return error */
+        return y.num == 0 ? lval_err(LERR_DIV_ZERO)
+                          : lval_num(x.num / y.num);
+    }
+    if (strcmp(op, "%") == 0) {return lval_num(x.num % y.num);}
+    if (strcmp(op, "^") == 0) {return lval_num(pow(x.num, y.num));}
+    if (strcmp(op, "min") == 0) {return lval_num(min(x.num, y.num));}
+    if (strcmp(op, "max") == 0) {return lval_num(max(x.num, y.num));}
+
+    return lval_err(LERR_BAD_OP);
+}
+
+
+lval eval(mpc_ast_t* t) {
+
+    if (strstr(t->tag, "number")) {
+        /* Check if there is some error in conversion */
+        errno = 0;
+        long x = strtol(t->contents, NULL, 10);
+        return errno != ERANGE ? lval_num(x) : lval_err(LERR_BAD_NUM);
+    }
+
+    /* The operator is always second child */
+    char* op = t->children[1]->contents;
+
+    /* We store the third children in x */
+    lval 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 : '+' | '-' | '*' | '/' | '%' | '^' |      \
+            \"min\" | \"max\" ;                                 \
+            expr     : <number> | '(' <operator> <expr>+ ')' ;  \
+            lispy    : /^/ <operator> <expr>+ /$/ ;             \
+        ",
+        Number, Operator, Expr, Lispy);
+
+    /* Print version and exit information */
+    puts("Lispy version 0.0.0.0.4");
+    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 */
+            lval result = eval(r.output);
+            lval_println(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;
+}