initial version

oper.c

@@ -0,0 +1,58 @@
+#include <string.h>
+#include <malloc.h>
+#include "lceb.h"
+
+unsigned ncombinations(nops, len)
+    int nops, len;
+{
+    int result = 1;
+    while(len > 0){
+        if(len & 1)
+            result *= nops;
+        nops *= nops;
+        len >>=1;
+    }
+    return result;
+}
+
+char *combination(ops, len, n)
+    char *ops;                                    /* string to combine */
+    int len;                                      /* len of result */
+    int n;                                        /* iteration # */
+{
+    static char *res=NULL;
+    static int len_ops;
+    int i;
+
+    if (!res) {                                   // 1st call
+        len_ops=strlen(ops);
+        res=malloc(len * sizeof(char) + 1);
+    }
+    for(i=0; i<len; ++i){
+        res[len -i -1] = ops[n % len_ops];
+        n /= len_ops;
+    }
+    return res;
+}
+
+#ifdef STANDALONE
+int main(ac, av)
+    int ac;
+    char **av;
+{
+    char *ops="+-*/", *p;
+    int len_ops=strlen(ops);
+    int i, j, nops, ncombs;
+
+    nops=atoi(*(av+1));
+    ncombs=ncombinations(len_ops, nops);
+    printf("# operators combinations : %d\nlist = ", ncombs);
+    for (i=0; i<ncombs; ++i) {
+        p=combination(ops, nops, i);
+        printf("[%s]\n", p);
+        //for (j=0; j<4; ++j)
+        //    distribute(j, p);
+        //printf("\n");
+    }
+}
+#endif