Improved an issue with cspan.

3 files changed, 22 insertions, 8 deletions

diff --git a/docs/cspan_api.md b/docs/cspan_api.md
index 1312ae6d..51d72856 100644
--- a/docs/cspan_api.md
+++ b/docs/cspan_api.md
@@ -29,6 +29,7 @@ by default (define `STC_NDEBUG` or `NDEBUG` to disable).
 ```c
 SpanType        cspan_init(TYPE SpanType, {v1, v2, ...});           // make a 1-d cspan from values
 SpanType        cspan_from(STCContainer* cnt);                      // make a 1-d cspan from a cvec, cstack, cpque (heap)
+SpanType        cspan_from_n(ValueType* ptr, intptr_t n);           // make a 1-d cspan from a pointer and length
 SpanType        cspan_from_array(ValueType array[]);                // make a 1-d cspan from a C array
 
 intptr_t        cspan_size(const SpanTypeN* self);                  // return number of elements
@@ -144,6 +145,7 @@ Slicing cspan without and with reducing the rank:
 ```c
 #define i_implement
 #include <c11/fmt.h>
+#include <stc/algorithm.h>
 #include <stc/cspan.h>
 
 using_cspan3(Span, int); // Shorthand to define Span, Span2, and Span3
@@ -164,6 +166,14 @@ int main(void)
         fmt_print(" {}", *i.ref);
     puts("");
 
+    // create span on-the-fly
+    int array[] = {3, 65, 4, 3, 7, 87, 45};
+    c_forfilter (i, ISpan, (ISpan)cspan_from_array(array),
+                    c_flt_skip(i, 2) &&
+                    c_flt_take(i, 3))
+        fmt_print(" {}", *i.ref);
+    puts("");
+
     // slice without reducing rank:
     Span3 ss3 = cspan_slice(Span3, &span3, {c_ALL}, {3,4}, {c_ALL});
 
diff --git a/include/stc/cspan.h b/include/stc/cspan.h
index 08045010..1b57d4d4 100644
--- a/include/stc/cspan.h
+++ b/include/stc/cspan.h
@@ -26,7 +26,7 @@
 #include <stc/cspan.h>
 #include <stc/algo/filter.h>
 using_cspan(Span2f, float, 2);
-using_cspan(Intspan, int, 1);
+using_cspan(Intspan, int);
 
 int demo1() {
     float raw[4*5];
@@ -65,7 +65,11 @@ int demo2() {
 
 #define using_cspan(...) c_MACRO_OVERLOAD(using_cspan, __VA_ARGS__)
 #define using_cspan_2(Self, T) \
-    using_cspan_3(Self, T, 1)
+    using_cspan_3(Self, T, 1); \
+    STC_INLINE Self Self##_from_n(Self##_raw* raw, const intptr_t n) { \
+        return (Self){.data=raw, .shape={(int32_t)n}, .stride={.d={1}}}; \
+    } \
+    struct stc_nostruct
 
 #define using_cspan_3(Self, T, RANK) \
     typedef T Self##_value; typedef T Self##_raw; \
@@ -77,9 +81,6 @@ int demo2() {
     \
     typedef struct { Self##_value *ref; int32_t pos[RANK]; const Self *_s; } Self##_iter; \
     \
-    STC_INLINE Self Self##_from_n(Self##_raw* raw, const intptr_t n) { \
-        return (Self){.data=raw, .shape={(int32_t)n}}; \
-    } \
     STC_INLINE Self Self##_slice_(Self##_value* d, const int32_t shape[], const int32_t stri[], \
                                   const int rank, const int32_t a[][2]) { \
         Self s; int outrank; \
@@ -104,7 +105,7 @@ int demo2() {
     } \
     struct stc_nostruct
 
-#define using_cspan2(Self, T) using_cspan_3(Self, T, 1); using_cspan_3(Self##2, T, 2)
+#define using_cspan2(Self, T) using_cspan_2(Self, T); using_cspan_3(Self##2, T, 2)
 #define using_cspan3(Self, T) using_cspan2(Self, T); using_cspan_3(Self##3, T, 3)
 #define using_cspan4(Self, T) using_cspan3(Self, T); using_cspan_3(Self##4, T, 4)
 #define using_cspan_tuple(N) typedef struct { int32_t d[N]; } cspan_tuple##N
@@ -124,8 +125,11 @@ using_cspan_tuple(7); using_cspan_tuple(8);
 #define cspan_from(container) \
     {.data=(container)->data, .shape={(int32_t)(container)->_len}, .stride={.d={1}}}
 
+#define cspan_from_n(ptr, n) \
+    {.data=(ptr), .shape={n}, .stride={.d={1}}}
+
 #define cspan_from_array(array) \
-    {.data=(array), .shape={c_arraylen(array)}, .stride={.d={1}}}
+    cspan_from_n(array, c_arraylen(array))
 
 #define cspan_size(self) _cspan_size((self)->shape, cspan_rank(self))
 #define cspan_rank(self) c_arraylen((self)->shape)
diff --git a/misc/examples/spans/printspan.c b/misc/examples/spans/printspan.c
index cd3c5f4f..eb9d80e3 100644
--- a/misc/examples/spans/printspan.c
+++ b/misc/examples/spans/printspan.c
@@ -11,7 +11,7 @@
 #include <stc/csset.h>
 
 #include <stc/cspan.h>
-using_cspan(intspan, int, 1);
+using_cspan(intspan, int);
 
 void printMe(intspan container) {
     printf("%d:", (int)cspan_size(&container));