Messing around replacing loops with recursion leveraging __attribute__((musttail)) in order to avoid stack overflow

6 files changed, 143 insertions, 49 deletions

diff --git a/ex1-10.c b/ex1-10.c
index 0b0c018..f17e748 100644
--- a/ex1-10.c
+++ b/ex1-10.c
@@ -6,31 +6,63 @@
 typedef enum _state {IN,OUT} state;
 
 /* true if c is a 'word' character (not a blank, space, or a tab)  */
-bool is_word(char c) {
+static bool is_word(char c) {
     return c != ' ' && c != '\t' && c != '\n';
 }
 
+struct res {
+    uint32_t cc;
+    uint32_t lc;
+    uint32_t wc;
+};
+
+struct res_internal {
+    struct res res;
+    state s;
+};
+
+static struct res_internal nri(void) {
+    struct res_internal res = {
+        .s = OUT,
+        .res = {
+            .cc = 0,
+            .lc = 0,
+            .wc = 0,
+        }
+    };
+    return res;
+}
+
+static struct res_internal do_count_internal(FILE* fin, struct res_internal res) {
+    int c = fgetc(fin);
+    if (c == EOF) {
+        return res;
+    }
+    res.res.cc++;
+    if (c == '\n') {
+        res.res.lc++;
+    }
+    if (!is_word(c)) {
+        res.s = OUT;
+    } else if (res.s == OUT) {
+        res.s = IN;
+        res.res.wc++;
+    }
+    __attribute__((musttail))
+    return do_count_internal(fin, res);
+}
+
+struct res do_count() {
+    struct res_internal ri = do_count_internal(stdin, nri());
+    return ri.res;
+}
 /* Counts characters, lines, and words from stdin. 
 
    'characters' are single byte characters. No handling for encodings in c standard lib.
    'lines' are newline characters.
    'words' are contiguous sequences of characters  other than space, tab, newline */
 int main(void) {
-    int c;
-    state s = OUT;
-    uint32_t cc = 0, lc = 0, wc = 0;
-    while ((c = getchar()) !=  EOF) {
-        cc++;
-        if (c == '\n') {
-            lc++;
-        }
-        if (!is_word(c)) {
-            s = OUT;
-        } else if (s == OUT) {
-            s = IN;
-            wc++;
-        }
-    }
-    printf("cc=%d lc=%d wc=%d\n", cc, lc, wc);
+    struct res res = do_count();
+    printf("cc=%d lc=%d wc=%d\n", res.cc, res.lc, res.wc);
     return 0;
 }
\ No newline at end of file
diff --git a/ex1-8.c b/ex1-8.c
index cc70b64..7e8c3bd 100644
--- a/ex1-8.c
+++ b/ex1-8.c
@@ -1,18 +1,43 @@
 #include <stdio.h>
 #include <stdint.h>
 
-int main(void) {
-  int c;
-  uint32_t nl = 0, tb = 0, bl = 0;
-  while ((c = getchar()) != EOF) {
-    if (c == ' ') {
-      bl++;
-    } else if (c == '\n') {
-      nl++;
-    } else if (c == '\t') {
-      tb++;
-    }
+struct res {
+  uint64_t nl;
+  uint64_t tb;
+  uint64_t bl;
+};
+
+struct res nr(void) {
+  struct res r = {
+    .nl = 0,
+    .tb = 0,
+    .bl = 0.
+  };
+  return r;
+}
+
+static struct res _loop(struct res res) {
+  int c = getchar();
+  if (c == EOF) {
+    return res;
   }
-  printf("nl=%ld tb=%ld bl=%ld\n", nl, tb, bl);
+  if (c == ' ') {
+     res = (struct res){
+      .bl = res.bl+1,
+      .nl = res.nl,
+      .tb = res.tb,
+    };
+  } else if (c == '\n') {
+    res.nl++;
+  } else if (c == '\t') {
+    res.tb++;
+  }
+  __attribute__((musttail))
+  return _loop(res);
+}
+
+int main(void) {
+  struct res r = _loop(nr());
+  printf("nl=%ld tb=%ld bl=%ld\n", r.nl, r.tb, r.bl);
   return 0;
 }
diff --git a/ex1-9.c b/ex1-9.c
index 07561d9..c2a625b 100644
--- a/ex1-9.c
+++ b/ex1-9.c
@@ -2,27 +2,29 @@
 #include <stdbool.h>
 #include <string.h>
 
-/* Copy stdin to stdout, replacing consecutive spaces with a single space
-   Edge case: a leading space is retained if there are leading spaces.
-   Edge case: an empty file just doesn't echo anything, but emits a warning on stderr */
-int remspace(FILE* fin, FILE* fout, FILE* ferr) {
-  int c = fgetc(fin);
-  if (c == EOF) {
-    fprintf(ferr, "warning: no input\n");
-    goto exit;
-  }
-  fputc(c, fout);
-  bool bl = (c == ' ');
-  while ((c = fgetc(fin)) != EOF) {
-    if ((!bl) || (c != ' ')) {
+static int _remspace_internal(FILE* fin, FILE* fout, FILE* ferr, int pc) {
+    int c = fgetc(fin);
+    if (c == EOF) {
+        // Should I still put EOF here? does it work with pipes or not?
+        //fputc(c, fout);
+        return 0;
+    }
+    if (c == ' ' && pc == ' ') {
+        // skip it
+    } else {
         fputc(c, fout);
     }
-    bl = (c == ' ');
-  }
-exit:
+    __attribute__((musttail))
+    return _remspace_internal(fin, fout, ferr, c);
+}
+
+/* Copy stdin to stdout, replacing consecutive spaces with a single space
+   Edge case: a leading space is retained if there are leading spaces. */
+int remspace(FILE* fin, FILE* fout, FILE* ferr) {
+  int res = _remspace_internal(fin, fout, ferr, -1);
   fflush(fout);
   fflush(ferr);
-  return 0;
+  return res;
 }
 
 #ifndef test
@@ -47,7 +49,7 @@ void do_test(CuTest* tc, char* input, const char* expected, const char* err_expe
     CuAssertStrEquals(tc, err_expected, err_buf);
 }
 void test_remspace_empty(CuTest* tc) {
-    do_test(tc, "", "", "warning: no input\n");
+    do_test(tc, "", "", "");
 }
 void test_remspace_oneword(CuTest* tc) {
     do_test(tc, "foobar", "foobar", "");
diff --git a/fib.c b/fib.c
new file mode 100644
index 0000000..6f510c2
--- /dev/null
+++ b/fib.c
@@ -0,0 +1,35 @@
+#include <stdio.h>
+
+static long fib_internal(int n, long a, long b) {
+    if (n == 0) {
+        return a;
+    } else if (n == 1) {
+        return b;
+    } else {
+        __attribute__((musttail))
+        return fib_internal(n-1, b, a + b);
+    }
+}
+
+long fib(int n) {
+    return fib_internal(n, 0, 1);
+}
+
+void test(int n) {
+    printf("fib [%d] = [%ld]\n", n, fib(n));
+}
+
+// static long recursion_depth(long n, long max) {
+//     if (n >= max) {
+//         return n;
+//     }
+//     __attribute__((musttail))
+//     return recursion_depth(n+1, max);
+// }
+
+int main(void) {
+    for (int i=1; i<300; i++) {
+        test(i);
+    }
+    //printf("%ld\n", recursion_depth(0, 1000000000));
+}
\ No newline at end of file
diff --git a/run b/run
index 11c2851..96e9fac 100755
--- a/run
+++ b/run
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 set -e
-cc -o exe $@
+clang -Wall -Werror -o exe $@
 ./exe
 result=$?
 rm exe
diff --git a/test b/test
index 4e32886..77c4f7d 100755
--- a/test
+++ b/test
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 set -e
-cc -Dtest=true -o test_exe CuTest.c $@ 
+clang -Wall -Werror -Dtest=true -o test_exe CuTest.c $@ 
 ./test_exe
 result=$?
 rm test_exe