136 lines
2.3 KiB
C
136 lines
2.3 KiB
C
#include "runtime.h"
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box_t cons(box_t car, box_t cdr) {
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cons_t* kons = alloc();
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kons->car = car;
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kons->cdr = cdr;
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box_t box;
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box.type = CONS;
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box.cons = kons;
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return box;
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}
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void chomp_ws() {
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char c = getchar();
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for(;;) {
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if (c == ' ' || c == '\t' || c == '\n' || c == '\r') {
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c = getchar();
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} else {
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ungetchar(c);
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break;
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}
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}
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}
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box_t read_integer() {
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char buf[256];
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size_t i = 0;
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char next = getchar();
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while(isdigit(next)) {
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buf[i] = next;
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next = getchar();
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i++;
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}
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ungetchar(next);
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buf[i] = 0;
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box_t res;
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res.type = INTEGER;
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res.integer = atoi(buf);
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chomp_ws();
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return res;
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}
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box_t read_symbol() {
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char buf[256];
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size_t i = 0;
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char next = getchar();
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while (isalpha(next)) { // Totally insufficent but we'll look into it later
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buf[i] = next;
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next = getchar();
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i++;
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}
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ungetchar(next);
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buf[i] = 0;
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box_t res;
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char *str = strndup(buf, i);
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res.type = SYMBOL;
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res.symbol = str;
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chomp_ws(); // Clean up whitespace afterwards
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return res;
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}
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box_t read_list() {
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char c = getchar();
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box_t val;
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if (c == ')') {
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chomp_ws();
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val.type = CONS;
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val.cons = the_empty_list;
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return val;
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} else {
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ungetchar(c);
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box_t car = read();
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box_t cdr = read_list();
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return cons(car, cdr);
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}
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}
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box_t read() {
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chomp_ws();
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char next = getchar();
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if (next == '(') {
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chomp_ws();
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return read_list();
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} else if (isdigit(next)) {
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ungetchar(next);
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return read_integer();
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} else if (isalpha(next) || ispunct(next)) {
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ungetchar(next);
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return read_symbol();
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} else if (next == EOF) {
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box_t bye;
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bye.type = BYE;
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return bye;
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} else {
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fprintf(stderr, "Bad input");
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exit(1);
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}
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}
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void scm_print_cons(box_t exp) {
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printf("(");
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while(exp.type = CONS && exp.cons != the_empty_list) {
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scm_print(exp.cons->car);
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if (exp.cons->cdr.cons != the_empty_list) {
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printf(" ");
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}
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exp = exp.cons->cdr;
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}
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if (exp.cons == the_empty_list) {
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printf(")");
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} else {
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printf(". ");
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scm_print(exp);
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printf(")");
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}
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}
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void scm_print(box_t exp) {
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switch (exp.type) {
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case INTEGER:
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printf("%d", exp.integer);
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break;
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case SYMBOL:
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printf("%s", exp.symbol);
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break;
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case CONS:
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scm_print_cons(exp);
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break;
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}
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}
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box_t eval(box_t exp) {
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return exp;
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}
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