API CHANGES:

Changed csview: becomes a null-terminated string view.
Added csubview: a null-terminated string view/span, like previous csview.

Note that csview works like a csubview, so not much compability issues should arise.
However, some functions have changed from _sv suffix to _ss.

6 files changed, 281 insertions, 163 deletions

diff --git a/docs/cmap_api.md b/docs/cmap_api.md
index 4e6da57d..65777221 100644
--- a/docs/cmap_api.md
+++ b/docs/cmap_api.md
@@ -282,7 +282,7 @@ typedef struct {
     cstr country;
 } Viking;
 
-#define Viking_init() ((Viking){cstr_null, cstr_null})
+#define Viking_init() ((Viking){.name={0}, .country={0}})
 
 static inline int Viking_cmp(const Viking* a, const Viking* b) {
     int c = cstr_cmp(&a->name, &b->name);
diff --git a/docs/coroutine_api.md b/docs/coroutine_api.md
index f7d81a34..c44f4a4d 100644
--- a/docs/coroutine_api.md
+++ b/docs/coroutine_api.md
@@ -237,7 +237,7 @@ cco_task_struct (produce_items,
 int produce_items(struct produce_items* p, cco_runtime* rt)
 {
     cco_routine (p) {
-        p->str = cstr_null;
+        p->str = cstr_init();
         p->next.cco_func = next_value;
         while (true)
         {
diff --git a/docs/cregex_api.md b/docs/cregex_api.md
index 52476e09..98161fe9 100644
--- a/docs/cregex_api.md
+++ b/docs/cregex_api.md
@@ -33,11 +33,11 @@ int         cregex_compile(cregex *self, const char* pattern, int cflags = CREG_
 int         cregex_captures(const cregex* self); 
 
             // return CREG_OK, CREG_NOMATCH, or CREG_MATCHERROR
-int         cregex_find(const cregex* re, const char* input, csview match[], int mflags = CREG_DEFAULT);
+int         cregex_find(const cregex* re, const char* input, csubstr match[], int mflags = CREG_DEFAULT);
             // Search inside input string-view only
-int         cregex_find_sv(const cregex* re, csview input, csview match[]);
+int         cregex_find_ss(const cregex* re, csubstr input, csubstr match[]);
             // All-in-one search (compile + find + drop)
-int         cregex_find_pattern(const char* pattern, const char* input, csview match[], int cmflags = CREG_DEFAULT);
+int         cregex_find_pattern(const char* pattern, const char* input, csubstr match[], int cmflags = CREG_DEFAULT);
 
             // Check if there are matches in input
 bool        cregex_is_match(const cregex* re, const char* input);
@@ -45,14 +45,14 @@ bool        cregex_is_match(const cregex* re, const char* input);
             // Replace all matches in input
 cstr        cregex_replace(const cregex* re, const char* input, const char* replace, int count = INT_MAX);
             // Replace count matches in input string-view. Optionally transform replacement.
-cstr        cregex_replace_sv(const cregex* re, csview input, const char* replace, int count = INT_MAX);
-cstr        cregex_replace_sv(const cregex* re, csview input, const char* replace, int count,
-                              bool(*transform)(int group, csview match, cstr* result), int rflags);
+cstr        cregex_replace_ss(const cregex* re, csubstr input, const char* replace, int count = INT_MAX);
+cstr        cregex_replace_ss(const cregex* re, csubstr input, const char* replace, int count,
+                              bool(*transform)(int group, csubstr match, cstr* result), int rflags);
 
             // All-in-one replacement (compile + find/replace + drop)
 cstr        cregex_replace_pattern(const char* pattern, const char* input, const char* replace, int count = INT_MAX);
 cstr        cregex_replace_pattern(const char* pattern, const char* input, const char* replace, int count,
-                                   bool(*transform)(int group, csview match, cstr* result), int rflags);
+                                   bool(*transform)(int group, csubstr match, cstr* result), int rflags);
             // destroy
 void        cregex_drop(cregex* self);
 ```
@@ -109,9 +109,9 @@ int main(void) {
     cregex re = cregex_from(pattern);
 
     // Lets find the first date in the string:
-    csview match[4]; // full-match, year, month, date.
+    csubstr match[4]; // full-match, year, month, date.
     if (cregex_find(&re, input, match) == CREG_OK)
-        printf("Found date: %.*s\n", c_SV(match[0]));
+        printf("Found date: %.*s\n", c_SS(match[0]));
     else
         printf("Could not find any date\n");
 
@@ -127,7 +127,7 @@ int main(void) {
 For a single match you may use the all-in-one function:
 ```c
 if (cregex_find_pattern(pattern, input, match))
-    printf("Found date: %.*s\n", c_SV(match[0]));
+    printf("Found date: %.*s\n", c_SS(match[0]));
 ```
 
 To use: `gcc first_match.c src/cregex.c src/utf8code.c`.
@@ -137,16 +137,16 @@ In order to use a callback function in the replace call, see `examples/regex_rep
 
 To iterate multiple matches in an input string, you may use
 ```c
-csview match[5] = {0};
+csubstr match[5] = {0};
 while (cregex_find(&re, input, match, CREG_NEXT) == CREG_OK)
     for (int k = 1; i <= cregex_captures(&re); ++k)
-        printf("submatch %d: %.*s\n", k, c_SV(match[k]));
+        printf("submatch %d: %.*s\n", k, c_SS(match[k]));
 ```
 There is also a for-loop macro to simplify it:
 ```c
 c_formatch (it, &re, input)
     for (int k = 1; i <= cregex_captures(&re); ++k)
-        printf("submatch %d: %.*s\n", k, c_SV(it.match[k]));
+        printf("submatch %d: %.*s\n", k, c_SS(it.match[k]));
 ```
 
 ## Using cregex in a project
@@ -154,7 +154,7 @@ c_formatch (it, &re, input)
 The easiest is to `#define i_import` before `#include <stc/cregex.h>`. Make sure to do that in one translation unit only.
 
 For reference, **cregex** uses the following files: 
-- `stc/cregex.h`, `stc/utf8.h`, `stc/csview.h`, `stc/cstr.h`, `stc/ccommon.h`, `stc/forward.h`
+- `stc/cregex.h`, `stc/utf8.h`, `stc/csubstr.h`, `stc/cstr.h`, `stc/ccommon.h`, `stc/forward.h`
 - `src/cregex.c`, `src/utf8code.c`.
 
 ## Regex Cheatsheet
diff --git a/docs/cstr_api.md b/docs/cstr_api.md
index dae5669f..36606b76 100644
--- a/docs/cstr_api.md
+++ b/docs/cstr_api.md
@@ -18,11 +18,11 @@ All cstr definitions and prototypes are available by including a single header f
 
 ## Methods
 ```c
-cstr        cstr_init(void);                                        // constructor; same as cstr_null.
+cstr        cstr_init(void);                                        // constructor; empty string
 cstr        cstr_lit(const char literal_only[]);                    // cstr from literal; no strlen() call.
 cstr        cstr_from(const char* str);                             // constructor using strlen()
 cstr        cstr_from_n(const char* str, intptr_t n);               // constructor with n first bytes of str
-cstr        cstr_from_sv(csview sv);                                // construct cstr from csview
+cstr        cstr_from_ss(csubstr sv);                                // construct cstr from csubstr
 cstr        cstr_with_capacity(intptr_t cap);
 cstr        cstr_with_size(intptr_t len, char fill);                // repeat fill len times
 cstr        cstr_from_fmt(const char* fmt, ...);                    // printf() formatting
@@ -34,7 +34,7 @@ void        cstr_drop(cstr* self);                                  // destructo
 
 const char* cstr_str(const cstr* self);                             // cast to const char*
 char*       cstr_data(cstr* self);                                  // cast to mutable char*
-csview      cstr_sv(const cstr* self);                              // cast to string view
+csubstr      cstr_ss(const cstr* self);                              // cast to string view
 cstr_buf    cstr_buffer(cstr* self);                                // cast to mutable buffer (with capacity)
 
 intptr_t    cstr_size(const cstr* self);
@@ -48,13 +48,13 @@ void        cstr_clear(cstr* self);
 
 char*       cstr_assign(cstr* self, const char* str);
 char*       cstr_assign_n(cstr* self, const char* str, intptr_t n); // assign n first bytes of str
-char*       cstr_assign_sv(cstr* self, csview sv);
+char*       cstr_assign_ss(cstr* self, csubstr sv);
 char*       cstr_copy(cstr* self, cstr s);                          // copy-assign a cstr
 int         cstr_printf(cstr* self, const char* fmt, ...);          // source and target must not overlap.
 
 char*       cstr_append(cstr* self, const char* str);
 char*       cstr_append_n(cstr* self, const char* str, intptr_t n); // append n first bytes of str
-char*       cstr_append_sv(cstr* self, csview str);
+char*       cstr_append_ss(cstr* self, csubstr str);
 char*       cstr_append_s(cstr* self, cstr str);
 int         cstr_append_fmt(cstr* self, const char* fmt, ...);      // printf() formatting
 char*       cstr_append_uninit(cstr* self, intptr_t len);           // return ptr to start of uninited data
@@ -63,19 +63,19 @@ void        cstr_push(cstr* self, const char* chr);                 // append on
 void        cstr_pop(cstr* self);                                   // pop one utf8 char
 
 void        cstr_insert(cstr* self, intptr_t pos, const char* ins);
-void        cstr_insert_sv(cstr* self, intptr_t pos, csview ins);
+void        cstr_insert_ss(cstr* self, intptr_t pos, csubstr ins);
 void        cstr_insert_s(cstr* self, intptr_t pos, cstr ins);
 
 void        cstr_erase(cstr* self, intptr_t pos, intptr_t len);     // erase len bytes from pos
 
 void        cstr_replace(cstr* self, const char* search, const char* repl, unsigned count = MAX_INT);
-cstr        cstr_replace_sv(csview in, csview search, csview repl, unsigned count);
+cstr        cstr_replace_ss(csubstr in, csubstr search, csubstr repl, unsigned count);
 void        cstr_replace_at(cstr* self, intptr_t pos, intptr_t len, const char* repl); // replace at a pos
-void        cstr_replace_at_sv(cstr* self, intptr_t pos, intptr_t len, const csview repl);
+void        cstr_replace_at_ss(cstr* self, intptr_t pos, intptr_t len, const csubstr repl);
 void        cstr_replace_at_s(cstr* self, intptr_t pos, intptr_t len, cstr repl);
 
 bool        cstr_equals(const cstr* self, const char* str);
-bool        cstr_equals_sv(const cstr* self, csview sv);
+bool        cstr_equals_ss(const cstr* self, csubstr sv);
 bool        cstr_equals_s(const cstr* self, cstr s);
 
 intptr_t    cstr_find(const cstr* self, const char* search);
@@ -83,11 +83,11 @@ intptr_t    cstr_find_at(const cstr* self, intptr_t pos, const char* search); //
 bool        cstr_contains(const cstr* self, const char* search);
 
 bool        cstr_starts_with(const cstr* self, const char* str);
-bool        cstr_starts_with_sv(const cstr* self, csview sv);
+bool        cstr_starts_with_ss(const cstr* self, csubstr sv);
 bool        cstr_starts_with_s(const cstr* self, cstr s);
 
 bool        cstr_ends_with(const cstr* self, const char* str);
-bool        cstr_ends_with_sv(const cstr* self, csview sv);
+bool        cstr_ends_with_ss(const cstr* self, csubstr sv);
 bool        cstr_ends_with_s(const cstr* self, cstr s);
 
 bool        cstr_getline(cstr *self, FILE *stream);                 // cstr_getdelim(self, '\n', stream)
@@ -100,8 +100,8 @@ intptr_t    cstr_u8_size(const cstr* self);                         // number of
 intptr_t    cstr_u8_size_n(const cstr self, intptr_t nbytes);       // utf8 size within n bytes  
 intptr_t    cstr_u8_to_pos(const cstr* self, intptr_t u8idx);       // byte pos offset at utf8 codepoint index
 const char* cstr_u8_at(const cstr* self, intptr_t u8idx);           // char* position at utf8 codepoint index
-csview      cstr_u8_chr(const cstr* self, intptr_t u8idx);          // get utf8 character as a csview
-void        cstr_u8_replace_at(cstr* self, intptr_t bytepos, intptr_t u8len, csview repl); // replace u8len utf8 chars
+csubstr     cstr_u8_chr(const cstr* self, intptr_t u8idx);          // get utf8 character as a csubstr
+void        cstr_u8_replace_at(cstr* self, intptr_t bytepos, intptr_t u8len, csubstr repl); // replace u8len utf8 chars
 void        cstr_u8_erase(cstr* self, intptr_t bytepos, intptr_t u8len); // erase u8len codepoints from pos
 
 // iterate utf8 codepoints
@@ -112,14 +112,14 @@ cstr_iter   cstr_advance(cstr_iter it, intptr_t n);
 
 // utf8 functions requires linking with src/utf8code.c symbols:
 bool        cstr_valid_utf8(const cstr* self);                      // check if str is valid utf8
-cstr        cstr_casefold_sv(csview sv);                            // returns new casefolded utf8 cstr
+cstr        cstr_casefold_ss(csubstr sv);                           // returns new casefolded utf8 cstr
 
 cstr        cstr_tolower(const char* str);                          // returns new lowercase utf8 cstr
-cstr        cstr_tolower_sv(csview sv);                             // returns new lowercase utf8 cstr
+cstr        cstr_tolower_ss(csubstr sv);                            // returns new lowercase utf8 cstr
 void        cstr_lowercase(cstr* self);                             // transform cstr to lowercase utf8
 
 cstr        cstr_toupper(const char* str);                          // returns new uppercase utf8 cstr
-cstr        cstr_toupper_sv(csview sv);                             // returns new uppercase utf8 cstr
+cstr        cstr_toupper_ss(csubstr sv);                            // returns new uppercase utf8 cstr
 void        cstr_uppercase(cstr* self);                             // transform cstr to uppercase utf8
  
 int         cstr_icmp(const cstr* s1, const cstr* s2);              // utf8 case-insensitive comparison
@@ -132,11 +132,10 @@ Note that all methods with arguments `(..., const char* str, intptr_t n)`, `n` m
 
 #### Helper methods:
 ```c
-int          cstr_cmp(const cstr* s1, const cstr* s2);
-bool         cstr_eq(const cstr* s1, const cstr* s2);
-bool         cstr_hash(const cstr* self);
-
-char*        cstrnstrn(const char* str, const char* search, intptr_t slen, intptr_t nlen);
+int         cstr_cmp(const cstr* s1, const cstr* s2);
+bool        cstr_eq(const cstr* s1, const cstr* s2);
+bool        cstr_hash(const cstr* self);
+char*       cstrnstrn(const char* str, const char* search, intptr_t slen, intptr_t nlen);
 ```
 
 ## Types
@@ -145,7 +144,7 @@ char*        cstrnstrn(const char* str, const char* search, intptr_t slen, intpt
 |:----------------|:---------------------------------------------|:---------------------|
 | `cstr`          | `struct { ... }`                             | The string type      |
 | `cstr_value`    | `char`                                       | String element type  |
-| `csview`        | `struct { const char *str; intptr_t size; }` | String view type     |
+| `csubstr`       | `struct { const char *str; intptr_t size; }` | String view type     |
 | `cstr_buf`      | `struct { char *data; intptr_t size, cap; }` | String buffer type   |
 
 ## Constants and macros
@@ -153,7 +152,6 @@ char*        cstrnstrn(const char* str, const char* search, intptr_t slen, intpt
 | Name              | Value             |
 |:------------------|:------------------|
 |  `c_NPOS`         | `INTPTR_MAX`      |
-|  `cstr_null`      | empty cstr value  |
 
 ## Example
 ```c
diff --git a/docs/csubstr_api.md b/docs/csubstr_api.md
new file mode 100644
index 00000000..925c69db
--- /dev/null
+++ b/docs/csubstr_api.md
@@ -0,0 +1,217 @@
+# STC [csubstr](../include/stc/csubstr.h): String View
+![String](pics/string.jpg)
+
+The type **csubstr** is a string view and can refer to a constant contiguous sequence of char-elements with the first
+element of the sequence at position zero. The implementation holds two members: a pointer to constant char and a size.
+
+**csubstr** is non-null terminated, and therefore not a replacent for `const char*` - see [csview](csview_api.md) for
+that. **csubstr** never allocates memory, and therefore need not be destructed.
+Its lifetime is limited by the source string storage. It keeps the length of the string, and does not need to call
+*strlen()* to acquire the length.
+
+Note: a **csubstr** may ***not be null-terminated***, and must therefore be printed this way:
+```c
+printf("%.*s", c_SS(sstr))
+```
+
+See the c++ class [std::basic_string_view](https://en.cppreference.com/w/cpp/string/basic_string_view) for a functional
+description.
+
+## Header file
+
+All csubstr definitions and prototypes are available by including a single header file.
+
+```c
+#define i_implement
+#include <stc/cstr.h>
+#include <stc/csubstr.h> // after cstr.h: include extra cstr-csubstr functions
+```
+## Methods
+
+```c
+csubstr         c_ss(const char literal_only[]);                        // construct from literal, no strlen()
+csubstr         c_ss(const char* str, intptr_t n);                      // construct from str and length n
+csubstr         csubstr_from(const char* str);                           // construct from const char*
+csubstr         csubstr_from_n(const char* str, intptr_t n);             // alias for c_ss(str, n)
+
+intptr_t        csubstr_size(csubstr sv);
+bool            csubstr_empty(csubstr sv);
+void            csubstr_clear(csubstr* self);
+
+bool            csubstr_equals(csubstr sv, csubstr sv2);
+intptr_t        csubstr_find(csubstr sv, const char* str);
+intptr_t        csubstr_find_ss(csubstr sv, csubstr find);
+bool            csubstr_contains(csubstr sv, const char* str);
+bool            csubstr_starts_with(csubstr sv, const char* str);
+bool            csubstr_ends_with(csubstr sv, const char* str);
+
+csubstr         csubstr_substr_ex(csubstr sv, intptr_t pos, intptr_t n);  // negative pos count from end
+csubstr         csubstr_slice_ex(csubstr sv, intptr_t p1, intptr_t p2);   // negative p1, p2 count from end
+csubstr         csubstr_token(csubstr sv, const char* sep, intptr_t* start); // *start > sv.size after last token
+```
+
+#### UTF8 methods
+```c
+intptr_t        csubstr_u8_size(csubstr sv);
+csubstr         csubstr_u8_substr(csubstr sv, intptr_t bytepos, intptr_t u8len);
+bool            csubstr_valid_utf8(csubstr sv);                           // requires linking with src/utf8code.c
+
+csubstr_iter    csubstr_begin(const csubstr* self);
+csubstr_iter    csubstr_end(const csubstr* self);
+void            csubstr_next(csubstr_iter* it);                           // utf8 codepoint step, not byte!
+csubstr_iter    csubstr_advance(csubstr_iter it, intptr_t n);
+```
+
+#### Extended cstr methods
+```c
+csubstr         cstr_substr(const cstr* self, intptr_t pos, intptr_t n);
+csubstr         cstr_substr_ex(const cstr* s, intptr_t pos, intptr_t n); // negative pos count from end
+csubstr         cstr_u8_substr(const cstr* self, intptr_t bytepos, intptr_t u8len);
+
+csubstr         cstr_slice(const cstr* self, intptr_t p1, intptr_t p2);
+csubstr         cstr_slice_ex(const cstr* s, intptr_t p, intptr_t q);    // negative p or q count from end
+```
+#### Iterate tokens with *c_fortoken*, *c_fortoken_ss*
+
+To iterate tokens in an input string separated by a string:
+```c
+c_fortoken (i, "hello, one, two, three", ", ")
+    printf("token: %.*s\n", c_SS(i.token));
+```
+
+#### Helper methods
+```c
+int             csubstr_cmp(const csubstr* x, const csubstr* y);
+int             csubstr_icmp(const csubstr* x, const csubstr* y);
+bool            csubstr_eq(const csubstr* x, const csubstr* y);
+uint64_t        csubstr_hash(const csubstr* x);
+```
+
+## Types
+
+| Type name       | Type definition                            | Used to represent...     |
+|:----------------|:-------------------------------------------|:-------------------------|
+| `csubstr`        | `struct { const char *str; intptr_t size; }` | The string view type     |
+| `csubstr_value`  | `char`                                     | The string element type  |
+| `csubstr_iter`   | `struct { csubstr_value *ref; }`            | UTF8 iterator            |
+
+## Constants and macros
+
+| Name           | Value                | Usage                                        |
+|:---------------|:---------------------|:---------------------------------------------|
+| `c_SS(sv)`     | printf argument      | `printf("sv: %.*s\n", c_SS(sv));`            |
+
+## Example
+```c
+#define i_implement
+#include <stc/cstr.h>
+#include <stc/csubstr.h>
+
+int main(void)
+{
+    cstr str1 = cstr_lit("We think in generalities, but we live in details.");
+                                                            // (quoting Alfred N. Whitehead)
+
+    csubstr sv1 = cstr_substr_ex(&str1, 3, 5);               // "think"
+    intptr_t pos = cstr_find(&str1, "live");                // position of "live" in str1
+    csubstr sv2 = cstr_substr_ex(&str1, pos, 4);             // get "live"
+    csubstr sv3 = cstr_slice_ex(&str1, -8, -1);              // get "details"
+    printf("%.*s %.*s %.*s\n",
+        c_SS(sv1), c_SS(sv2), c_SS(sv3));
+    cstr s1 = cstr_lit("Apples are red");
+    cstr s2 = cstr_from_ss(cstr_substr_ex(&s1, -3, 3));     // "red"
+    cstr s3 = cstr_from_ss(cstr_substr_ex(&s1, 0, 6));      // "Apples"
+    printf("%s %s\n", cstr_str(&s2), cstr_str(&s3));
+
+    c_drop(cstr, &str1, &s1, &s2, &s3);
+}
+```
+Output:
+```
+think live details
+red Apples
+```
+
+### Example 2: UTF8 handling
+```c
+#define i_import // include dependent cstr, utf8 and cregex function definitions.
+#include <stc/cstr.h>
+
+int main(void)
+{
+    cstr s1 = cstr_lit("hell😀 w😀rld");
+
+    cstr_u8_replace_at(&s1, cstr_find(&s1, "😀rld"), 1, c_ss("ø"));
+    printf("%s\n", cstr_str(&s1));
+
+    c_foreach (i, cstr, s1)
+        printf("%.*s,", c_SS(i.u8.chr));
+
+    cstr_drop(&s1);
+}
+```
+Output:
+```
+hell😀 wørld
+h,e,l,l,😀, ,w,ø,r,l,d,
+```
+
+### Example 3: csubstr tokenizer (string split)
+Splits strings into tokens. *print_split()* makes **no** memory allocations or *strlen()* calls,
+and does not depend on null-terminated strings. *string_split()* function returns a vector of cstr.
+```c
+#include <stdio.h>
+#include <stc/csubstr.h>
+
+void print_split(csubstr input, const char* sep)
+{
+    c_fortoken_ss (i, input, sep)
+        printf("[%.*s]\n", c_SS(i.token));
+    puts("");
+}
+#define i_implement
+#include <stc/cstr.h>
+#define i_key_str
+#include <stc/cstack.h>
+
+cstack_str string_split(csubstr input, const char* sep)
+{
+    cstack_str out = cstack_str_init();
+    
+    c_fortoken_ss (i, input, sep)
+        cstack_str_push(&out, cstr_from_ss(i.token));
+
+    return out;
+}
+
+int main(void)
+{
+    print_split(c_ss("//This is a//double-slash//separated//string"), "//");
+    print_split(c_ss("This has no matching separator"), "xx");
+
+    cstack_str s = string_split(c_ss("Split,this,,string,now,"), ",");
+
+    c_foreach (i, cstack_str, s)
+        printf("[%s]\n", cstr_str(i.ref));
+    puts("");
+
+    cstack_str_drop(&s);
+}
+```
+Output:
+```
+[]
+[This is a]
+[double-slash]
+[separated]
+[string]
+
+[This has no matching separator]
+
+[Split]
+[this]
+[]
+[string]
+[now]
+[]
+```
diff --git a/docs/csview_api.md b/docs/csview_api.md
index 49e4f9d1..4fdff0d1 100644
--- a/docs/csview_api.md
+++ b/docs/csview_api.md
@@ -1,19 +1,14 @@
 # STC [csview](../include/stc/csview.h): String View
 ![String](pics/string.jpg)
 
-The type **csview** is a string view and can refer to a constant contiguous sequence of char-elements with the first
-element of the sequence at position zero. The implementation holds two members: a pointer to constant char and a size.
+The type **csview** is a ***null-terminated*** string view and refers to a constant contiguous sequence of
+char-elements with the first element of the sequence at position zero. The implementation holds two
+members: a pointer to constant char and a size. See [csubstr](csubstr_api.md) for a ***non null-terminated***
+string view/span type.
 
-**csview** is an efficient replacent for `const char*`. It never allocates memory, and therefore need not be destructed.
-Its lifetime is limited by the source string storage. It keeps the length of the string, and does not call *strlen()*
-when passing it around. It is faster when using`csview` as convertion type (raw) than `const char*` in associative
-containers with cstr keys.
-
-Note: a **csview** may ***not be null-terminated***, and must therefore be printed like: 
-`printf("%.*s", csview_ARG(sv))`.
-
-See the c++ class [std::basic_string_view](https://en.cppreference.com/w/cpp/string/basic_string_view) for a functional
-description.
+Because **csview** is null-terminated, it can be a more efficient replacent for `const char*`. It never
+allocates memory, and need therefore not be destructed. Its lifetime is limited by the source string
+storage. It keeps the length of the string, and does not call *strlen()* when passing it around.
 
 ## Header file
 
@@ -42,17 +37,12 @@ intptr_t        csview_find_sv(csview sv, csview find);
 bool            csview_contains(csview sv, const char* str);
 bool            csview_starts_with(csview sv, const char* str);
 bool            csview_ends_with(csview sv, const char* str);
-
-csview          csview_substr_ex(csview sv, intptr_t pos, intptr_t n);  // negative pos count from end
-csview          csview_slice_ex(csview sv, intptr_t p1, intptr_t p2);   // negative p1, p2 count from end
-csview          csview_token(csview sv, const char* sep, intptr_t* start); // *start > sv.size after last token
 ```
 
 #### UTF8 methods
 ```c
 intptr_t        csview_u8_size(csview sv);
-csview          csview_u8_substr(csview sv, intptr_t bytepos, intptr_t u8len);
-bool            csview_valid_utf8(csview sv);                           // requires linking with src/utf8code.c
+bool            csview_valid_utf8(csview sv);                           // depends on src/utf8code.c
 
 csview_iter     csview_begin(const csview* self);
 csview_iter     csview_end(const csview* self);
@@ -74,27 +64,10 @@ uint32_t        utf8_peek(const char* s);                               // codep
 uint32_t        utf8_peek_off(const char* s, int offset);               // codepoint value at utf8 pos (may be negative)
 ```
 
-#### Extended cstr methods
-```c
-csview          cstr_substr(const cstr* self, intptr_t pos, intptr_t n);
-csview          cstr_substr_ex(const cstr* s, intptr_t pos, intptr_t n); // negative pos count from end
-csview          cstr_u8_substr(const cstr* self, intptr_t bytepos, intptr_t u8len);
-
-csview          cstr_slice(const cstr* self, intptr_t p1, intptr_t p2);
-csview          cstr_slice_ex(const cstr* s, intptr_t p, intptr_t q);    // negative p or q count from end
-```
-#### Iterate tokens with *c_fortoken*, *c_fortoken_sv*
-
-To iterate tokens in an input string separated by a string:
-```c
-c_fortoken (i, "hello, one, two, three", ", ")
-    printf("token: %.*s\n", c_SV(i.token));
-```
-
 #### Helper methods
 ```c
 int             csview_cmp(const csview* x, const csview* y);
-int             csview_icmp(const csview* x, const csview* y);
+int             csview_icmp(const csview* x, const csview* y);          // depends on src/utf8code.c:
 bool            csview_eq(const csview* x, const csview* y);
 uint64_t        csview_hash(const csview* x);
 ```
@@ -107,46 +80,36 @@ uint64_t        csview_hash(const csview* x);
 | `csview_value`  | `char`                                     | The string element type  |
 | `csview_iter`   | `struct { csview_value *ref; }`            | UTF8 iterator            |
 
-## Constants and macros
-
-| Name           | Value                | Usage                                        |
-|:---------------|:---------------------|:---------------------------------------------|
-| `c_SV(sv)`     | printf argument      | `printf("sv: %.*s\n", c_SV(sv));`            |
-
-## Example
+## Example: UTF8 iteration and case conversion
 ```c
-#define i_implement
+#define i_import
 #include <stc/cstr.h>
 #include <stc/csview.h>
 
 int main(void)
 {
-    cstr str1 = cstr_lit("We think in generalities, but we live in details.");
-                                                            // (quoting Alfred N. Whitehead)
-
-    csview sv1 = cstr_substr_ex(&str1, 3, 5);               // "think"
-    intptr_t pos = cstr_find(&str1, "live");                // position of "live" in str1
-    csview sv2 = cstr_substr_ex(&str1, pos, 4);             // get "live"
-    csview sv3 = cstr_slice_ex(&str1, -8, -1);              // get "details"
-    printf("%.*s %.*s %.*s\n",
-        c_SV(sv1), c_SV(sv2), c_SV(sv3));
-    cstr s1 = cstr_lit("Apples are red");
-    cstr s2 = cstr_from_sv(cstr_substr_ex(&s1, -3, 3));     // "red"
-    cstr s3 = cstr_from_sv(cstr_substr_ex(&s1, 0, 6));      // "Apples"
-    printf("%s %s\n", cstr_str(&s2), cstr_str(&s3));
-
-    c_drop(cstr, &str1, &s1, &s2, &s3);
+    cstr str = cstr_from("Liberté, égalité, fraternité.");
+    csview sv = cstr_sv(&str);
+
+    c_foreach (i, csview, sv)
+        printf("%.*s ", c_SS(i.u8.chr));
+    puts("");
+
+    cstr_uppercase(&str);
+    printf("%s\n", cstr_str(&str));
+
+    cstr_drop(&str);
 }
 ```
 Output:
 ```
-think live details
-red Apples
+L i b e r t é ,   é g a l i t é ,   f r a t e r n i t é . 
+LIBERTÉ, ÉGALITÉ, FRATERNITÉ.
 ```
 
-### Example 2: UTF8 handling
+### Example 2: UTF8 replace
 ```c
-#define i_import // include dependent cstr, utf8 and cregex function definitions.
+#define i_import // include dependent utf8 definitions.
 #include <stc/cstr.h>
 
 int main(void)
@@ -157,7 +120,7 @@ int main(void)
     printf("%s\n", cstr_str(&s1));
 
     c_foreach (i, cstr, s1)
-        printf("%.*s,", c_SV(i.u8.chr));
+        printf("%.*s,", c_SS(i.u8.chr)); // u8.chr is a csubstr
 
     cstr_drop(&s1);
 }
@@ -167,63 +130,3 @@ Output:
 hell😀 wørld
 h,e,l,l,😀, ,w,ø,r,l,d,
 ```
-
-### Example 3: csview tokenizer (string split)
-Splits strings into tokens. *print_split()* makes **no** memory allocations or *strlen()* calls,
-and does not depend on null-terminated strings. *string_split()* function returns a vector of cstr.
-```c
-#include <stdio.h>
-#include <stc/csview.h>
-
-void print_split(csview input, const char* sep)
-{
-    c_fortoken_sv (i, input, sep)
-        printf("[%.*s]\n", c_SV(i.token));
-    puts("");
-}
-#define i_implement
-#include <stc/cstr.h>
-#define i_key_str
-#include <stc/cstack.h>
-
-cstack_str string_split(csview input, const char* sep)
-{
-    cstack_str out = cstack_str_init();
-    
-    c_fortoken_sv (i, input, sep)
-        cstack_str_push(&out, cstr_from_sv(i.token));
-
-    return out;
-}
-
-int main(void)
-{
-    print_split(c_sv("//This is a//double-slash//separated//string"), "//");
-    print_split(c_sv("This has no matching separator"), "xx");
-
-    cstack_str s = string_split(c_sv("Split,this,,string,now,"), ",");
-
-    c_foreach (i, cstack_str, s)
-        printf("[%s]\n", cstr_str(i.ref));
-    puts("");
-
-    cstack_str_drop(&s);
-}
-```
-Output:
-```
-[]
-[This is a]
-[double-slash]
-[separated]
-[string]
-
-[This has no matching separator]
-
-[Split]
-[this]
-[]
-[string]
-[now]
-[]
-```