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authorIndrajith K L2022-12-03 17:00:20 +0530
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+# v_printf/v_sprintf
+
+These are v implementations of the C language `printf` and `sprintf` functions.
+
+***Note: These functions are platform dependent in C, but in V they are platform independent.***
+
+### v_sprintf
+
+`v_sprintf` has a variable number of parameters.
+The first is a format string to control the appearance of the final string.
+Each format specifier (%s, %d, etc.) in the format string
+is replaced by the textual version of the following parameters.
+
+```v
+import strconv
+
+fn main() {
+ a := 'World'
+ s := strconv.v_sprintf('Hello %s!', a)
+ println(s)
+}
+```
+
+```
+Hello World!
+```
+
+### v_printf
+
+`v_printf` creates the same modified string as `v_sprintf`, using the same format specifiers,
+but it will immediately print the modified string to stdout instead of returning a string.
+
+### Syntax
+
+The syntax for a format specifier is:
+
+```
+%[parameter][flags][width][.precision][length]type
+```
+
+#### Flags field
+
+The Flags field may be zero or more (in any order) of:
+
+| Character | Description |
+| ----------- | ------------------------------------------------------------ |
+| `-` (minus) | Left-align the output of this specifier. (The default is to right-align the output.) |
+| `+` (plus) | Prepends a plus for positive signed-numeric types. positive = `+`, negative = `-`. (The default doesn't prepend anything to positive numbers.) |
+| `0` (zero) | When the 'width' option is specified, prepends zeros for numeric types. (The default prepends spaces.) For example, `printf("%4X",3)` produces ` 3`, while `printf("%04X",3)` produces `0003`. |
+
+#### Width field
+
+The Width field specifies a *maximum* number of characters to output,
+and is typically used to pad fixed-width fields in tabulated output,
+it causes truncation of oversized fields.
+
+The width field may be omitted, or it may be a numeric integer value,
+or may also be specified by a parameter when indicated by an asterisk `*`.
+For example, `v_printf("%*.s", 5, my_string)` will result in ` mystring` being printed,
+with a total width of 5 characters.
+
+#### Length field
+
+The Length field can be omitted or be any of:
+
+| Character | Description |
+| --------- | ------------------------------------------------------------ |
+| `hh` | For integer types, causes `printf` to expect an `byte` or `i8` argument. |
+| `h` | For integer types, causes `printf` to expect an `int16` or `u16` argument. |
+| `l` | For integer types, causes `printf` to expect an `i64` or `u64` argument. |
+| `ll` | For integer types, causes `printf` to expect an `i64` or `u64` argument. |
+| | |
+| | |
+
+#### Type field
+
+The Type field can be any of:
+
+| Character | Description |
+| --------- | ------------------------------------------------------------ |
+| `%` | Prints a literal `%` character (this type doesn't accept any flags, width, precision, length fields). |
+| `d`, `i` | `int` as a signed `int` `%d` and `%i` are synonymous for output. The size of the argument is specified by the length field. |
+| `u` | `unsigned int`. The size of the argument is specified by the length field. |
+| `f`, `F` | `double` in normal notation. `f` and `F` only differs in how the strings are printed: lowercase or uppercase. |
+| `e`, `E` | `double` in scientific notation.`e` and `E` only differs in how the strings are printed: lowercase or uppercase. |
+| `g`, `G` | `double` in automatic notation.`g` and `G` only differs in how the strings are printed: lowercase or uppercase. |
+| `x`, `X` | `unsigned int` as a hexadecimal number. `x` uses lower-case letters and `X` uses upper-case. |
+| `s` | string |
+| `p` | `void *` (pointer to void) in an implementation-defined format. |
+| `c` | `char` (character). |
+
+## Examples
+
+various types
+
+```v oksyntax
+a0 := u32(10)
+b0 := 200
+c0 := byte(12)
+s0 := 'ciAo'
+ch0 := `B`
+f0 := 0.312345
+f1 := 200000.0
+sc0 := 'ciao: [%-08u] %d %hhd [%8s] [%08X] [%-20.4f] [%-20.4f] [%c]'
+temp_s = strconv.v_sprintf(sc0, a0, b0, c0, s0, b0, f0, f1, ch0)
+println(temp_s)
+```
+
+```
+ciao: [10 ] 200 12 [ ciAo] [000000C8] [0.3123 ] [200000.0000 ] [B]
+```
+
+integer
+
+```v oksyntax
+a := byte(12)
+b := i16(13)
+c := 14
+d := i64(15)
+sc1 := '==>%hhd %hd %d %ld'
+temp_s = strconv.v_sprintf(sc1, a, b, c, d)
+println(temp_s)
+```
+
+```
+==>12 13 14 15
+```
+
+unsigned integer
+
+```v oksyntax
+a1 := byte(0xff)
+b1 := u16(0xffff)
+c1 := u32(0xffffffff)
+d1 := u64(-1)
+sc2 := '%hhu %hu %u %lu'
+temp_s = strconv.v_sprintf(sc2, a1, b1, c1, d1)
+println(temp_s)
+```
+
+```
+255 65535 4294967295 18446744073709551615
+```
+
+hexadecimal
+
+```v oksyntax
+a1 := byte(0xff)
+b1 := i16(0xffff)
+c1 := u32(0xffffffff)
+d1 := u64(-1)
+sc3 := '%hhx %hx %x %lx'
+temp_s = strconv.v_sprintf(sc3, a1, b1, c1, d1)
+println(temp_s)
+```
+
+```
+ff ffff ffffffff ffffffffffffffff
+```
+
+hexadecimal
+
+```v oksyntax
+a2 := 125
+sc7 := '[%9x] [%9X] [%-9x] [%-9X] [%09x] [%09X]'
+temp_s = strconv.v_sprintf(sc7, a2, a2, a2, a2, a2, a2)
+println(temp_s)
+```
+
+```
+[ 7d] [ 7D] [7d ] [7D ] [00000007d] [00000007D]
+```
+
+floating points
+
+```v oksyntax
+f0 := 0.312345
+f1 := 200000.0
+f2 := -1234.300e6
+f3 := 1234.300e-6
+sc4 := '[%-20.3e] [%20.3e] [%-020.3e] [%-020.3E] [%-020.3e] [%-020.3e]'
+temp_s = strconv.v_sprintf(sc4, f0, f1, f1, f1, f2, f3)
+println(temp_s)
+```
+
+```
+[3.123e-01 ] [ 2.000e+05] [2.000e+05 ] [2.000E+05 ] [-1.234e+09 ] [1.234e-03 ]
+```
+
+float automatic notations
+
+```v oksyntax
+mut ft := -1e-7
+mut x := 0
+sc8 := '[%20g][%20G]|'
+for x < 12 {
+ temp_s = strconv.v_sprintf(sc8, ft, ft)
+ println('$temp_s\n')
+ ft = ft * 10.0
+ x++
+}
+```
+
+```
+[ -1e-07][ -1E-07]|
+[ -1e-06][ -1E-06]|
+[ -1e-05][ -1E-05]|
+[ -0.0001][ -0.0001]|
+[ -0.001][ -0.001]|
+[ -0.01][ -0.01]|
+[ -0.1][ -0.1]|
+[ -1][ -1]|
+[ -10][ -10]|
+[ -100][ -100]|
+[ -1000][ -1000]|
+[ -10000][ -10000]|
+
+```
+
+## Utility functions
+
+The format module also has some utility functions:
+
+```v oksyntax nofmt
+// calling struct
+struct BF_param {
+ pad_ch byte = ` ` // padding char
+ len0 int = -1 // default len for whole the number or string
+ len1 int = 6 // number of decimal digits, if needed
+ positive bool = true // mandatory: the sign of the number passed
+ sign_flag bool = false // flag for print sign as prefix in padding
+ allign Align_text = .right // alignment of the string
+ rm_tail_zero bool = false // remove the tail zeros from floats
+}
+
+// utilities
+fn format_dec(d u64, p BF_param) string
+fn format_fl(f f64, p BF_param) string
+fn format_es(f f64, p BF_param) string
+fn remove_tail_zeros(s string) string
+```
+
+`format_dec` format the integer number using the parameters in the `BF_param` struct.
+
+`format_fl` format a float number in normal notation using the parameters in the `BF_param` struct.
+
+`format_es format a float number in scientific notation using the parameters in the BF_param`
+struct.
+
+`remove_tail_zeros` removes the tailing zeros from a floating point number as string.